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2016-12-11sparc64:Support User Probes for sparcAllen Pais1-0/+1
Signed-off-by: Eric Saint Etienne <eric.saint.etienne@oracle.com> Signed-off-by: Allen Pais <allen.pais@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-11-23treewide: Remove old email addressPeter Zijlstra1-1/+1
There were still a number of references to my old Red Hat email address in the kernel source. Remove these while keeping the Red Hat copyright notices intact. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31uprobes/x86: Make arch_uretprobe_is_alive(RP_CHECK_CALL) more cleverOleg Nesterov1-0/+1
The previous change documents that cleanup_return_instances() can't always detect the dead frames, the stack can grow. But there is one special case which imho worth fixing: arch_uretprobe_is_alive() can return true when the stack didn't actually grow, but the next "call" insn uses the already invalidated frame. Test-case: #include <stdio.h> #include <setjmp.h> jmp_buf jmp; int nr = 1024; void func_2(void) { if (--nr == 0) return; longjmp(jmp, 1); } void func_1(void) { setjmp(jmp); func_2(); } int main(void) { func_1(); return 0; } If you ret-probe func_1() and func_2() prepare_uretprobe() hits the MAX_URETPROBE_DEPTH limit and "return" from func_2() is not reported. When we know that the new call is not chained, we can do the more strict check. In this case "sp" points to the new ret-addr, so every frame which uses the same "sp" must be dead. The only complication is that arch_uretprobe_is_alive() needs to know was it chained or not, so we add the new RP_CHECK_CHAIN_CALL enum and change prepare_uretprobe() to pass RP_CHECK_CALL only if !chained. Note: arch_uretprobe_is_alive() could also re-read *sp and check if this word is still trampoline_vaddr. This could obviously improve the logic, but I would like to avoid another copy_from_user() especially in the case when we can't avoid the false "alive == T" positives. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134028.GA4786@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31uprobes: Add the "enum rp_check ctx" arg to arch_uretprobe_is_alive()Oleg Nesterov1-1/+6
arch/x86 doesn't care (so far), but as Pratyush Anand pointed out other architectures might want why arch_uretprobe_is_alive() was called and use different checks depending on the context. Add the new argument to distinguish 2 callers. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134026.GA4779@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31uprobes/x86: Reimplement arch_uretprobe_is_alive()Oleg Nesterov1-0/+1
Add the x86 specific version of arch_uretprobe_is_alive() helper. It returns true if the stack frame mangled by prepare_uretprobe() is still on stack. So if it returns false, we know that the probed function has already returned. We add the new return_instance->stack member and change the generic code to initialize it in prepare_uretprobe, but it should be equally useful for other architectures. TODO: this assumes that the probed application can't use multiple stacks (say sigaltstack). We will try to improve this logic later. Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134018.GA4766@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-31uprobes: Export 'struct return_instance', introduce arch_uretprobe_is_alive()Oleg Nesterov1-0/+10
Add the new "weak" helper, arch_uretprobe_is_alive(), used by the next patches. It should return true if this return_instance is still valid. The arch agnostic version just always returns true. The patch exports "struct return_instance" for the architectures which want to override this hook. We can also cleanup prepare_uretprobe() if we pass the new return_instance to arch_uretprobe_hijack_return_addr(). Tested-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134016.GA4762@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-10-22uprobes: Remove "weak" from function declarationsBjorn Helgaas1-7/+7
For the following interfaces: set_swbp() set_orig_insn() is_swbp_insn() is_trap_insn() uprobe_get_swbp_addr() arch_uprobe_ignore() arch_uprobe_copy_ixol() kernel/events/uprobes.c provides default definitions explicitly marked "weak". Some architectures provide their own definitions intended to override the defaults, but the "weak" attribute on the declarations applied to the arch definitions as well, so the linker chose one based on link order (see 10629d711ed7 ("PCI: Remove __weak annotation from pcibios_get_phb_of_node decl")). Remove the "weak" attribute from the declarations so we always prefer a non-weak definition over the weak one, independent of link order. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> CC: Victor Kamensky <victor.kamensky@linaro.org> CC: Oleg Nesterov <oleg@redhat.com> CC: David A. Long <dave.long@linaro.org> CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
2014-06-12Merge branch 'perf-core-for-linus' of ↵Linus Torvalds1-0/+4
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull more perf updates from Ingo Molnar: "A second round of perf updates: - wide reaching kprobes sanitization and robustization, with the hope of fixing all 'probe this function crashes the kernel' bugs, by Masami Hiramatsu. - uprobes updates from Oleg Nesterov: tmpfs support, corner case fixes and robustization work. - perf tooling updates and fixes from Jiri Olsa, Namhyung Ki, Arnaldo et al: * Add support to accumulate hist periods (Namhyung Kim) * various fixes, refactorings and enhancements" * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits) perf: Differentiate exec() and non-exec() comm events perf: Fix perf_event_comm() vs. exec() assumption uprobes/x86: Rename arch_uprobe->def to ->defparam, minor comment updates perf/documentation: Add description for conditional branch filter perf/x86: Add conditional branch filtering support perf/tool: Add conditional branch filter 'cond' to perf record perf: Add new conditional branch filter 'PERF_SAMPLE_BRANCH_COND' uprobes: Teach copy_insn() to support tmpfs uprobes: Shift ->readpage check from __copy_insn() to uprobe_register() perf/x86: Use common PMU interrupt disabled code perf/ARM: Use common PMU interrupt disabled code perf: Disable sampled events if no PMU interrupt perf: Fix use after free in perf_remove_from_context() perf tools: Fix 'make help' message error perf record: Fix poll return value propagation perf tools: Move elide bool into perf_hpp_fmt struct perf tools: Remove elide setup for SORT_MODE__MEMORY mode perf tools: Fix "==" into "=" in ui_browser__warning assignment perf tools: Allow overriding sysfs and proc finding with env var perf tools: Consider header files outside perf directory in tags target ...
2014-05-25ARM: 8043/1: uprobes need icache flush after xol writeVictor Kamensky1-0/+3
After instruction write into xol area, on ARM V7 architecture code need to flush dcache and icache to sync them up for given set of addresses. Having just 'flush_dcache_page(page)' call is not enough - it is possible to have stale instruction sitting in icache for given xol area slot address. Introduce arch_uprobe_ixol_copy weak function that by default calls uprobes copy_to_page function and than flush_dcache_page function and on ARM define new one that handles xol slot copy in ARM specific way flush_uprobe_xol_access function shares/reuses implementation with/of flush_ptrace_access function and takes care of writing instruction to user land address space on given variety of different cache types on ARM CPUs. Because flush_uprobe_xol_access does not have vma around flush_ptrace_access was split into two parts. First that retrieves set of condition from vma and common that receives those conditions as flags. Note ARM cache flush function need kernel address through which instruction write happened, so instead of using uprobes copy_to_page function changed code to explicitly map page and do memcpy. Note arch_uprobe_copy_ixol function, in similar way as copy_to_user_page function, has preempt_disable/preempt_enable. Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: David A. Long <dave.long@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2014-05-14uprobes/x86: Fix the wrong ->si_addr when xol triggers a trapOleg Nesterov1-0/+4
If the probed insn triggers a trap, ->si_addr = regs->ip is technically correct, but this is not what the signal handler wants; we need to pass the address of the probed insn, not the address of xol slot. Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in uprobes.h uses a macro to avoid include hell and ensure that it can be compiled even if an architecture doesn't define instruction_pointer(). Test-case: #include <signal.h> #include <stdio.h> #include <unistd.h> extern void probe_div(void); void sigh(int sig, siginfo_t *info, void *c) { int passed = (info->si_addr == probe_div); printf(passed ? "PASS\n" : "FAIL\n"); _exit(!passed); } int main(void) { struct sigaction sa = { .sa_sigaction = sigh, .sa_flags = SA_SIGINFO, }; sigaction(SIGFPE, &sa, NULL); asm ( "xor %ecx,%ecx\n" ".globl probe_div; probe_div:\n" "idiv %ecx\n" ); return 0; } it fails if probe_div() is probed. Note: show_unhandled_signals users should probably use this helper too, but we need to cleanup them first. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
2014-03-18uprobes: allow ignoring of probe hitsDavid A. Long1-0/+1
Allow arches to decided to ignore a probe hit. ARM will use this to only call handlers if the conditions to execute a conditionally executed instruction are satisfied. Signed-off-by: David A. Long <dave.long@linaro.org> Acked-by: Oleg Nesterov <oleg@redhat.com>
2013-11-20uprobes: Cleanup !CONFIG_UPROBES decls, unexport xol_areaOleg Nesterov1-27/+4
1. Don't include asm/uprobes.h unconditionally, we only need it if CONFIG_UPROBES. 2. Move the definition of "struct xol_area" into uprobes.c. Perhaps we should simply kill struct uprobes_state, it buys nothing. 3. Kill the dummy definition of uprobe_get_swbp_addr(), nobody except handle_swbp() needs it. 4. Purely cosmetic, but move the decl of uprobe_get_swbp_addr() up, close to other __weak helpers. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2013-11-20uprobes: Add uprobe_task->dup_xol_work/dup_xol_addrOleg Nesterov1-5/+16
uprobe_task->vaddr is a bit strange. The generic code uses it only to pass the additional argument to arch_uprobe_pre_xol(), and since it is always equal to instruction_pointer() this looks even more strange. And both utask->vaddr and and utask->autask have the same scope, they only have the meaning when the task executes the probed insn out-of-line, so it is safe to reuse both in UTASK_RUNNING state. This all means that logically ->vaddr belongs to arch_uprobe_task and we should probably move it there, arch_uprobe_pre_xol() can record instruction_pointer() itself. OTOH, it is also used by uprobe_copy_process() and dup_xol_work() for another purpose, this doesn't look clean and doesn't allow to move this member into arch_uprobe_task. This patch adds the union with 2 anonymous structs into uprobe_task. The first struct is autask + vaddr, this way we "almost" move vaddr into autask. The second struct has 2 new members for uprobe_copy_process() paths: ->dup_xol_addr which can be used instead ->vaddr, and ->dup_xol_work which can be used to avoid kmalloc() and simplify the code. Note that this union will likely have another member(s), we need something like "private_data_for_handlers" so that the tracing handlers could use it to communicate with call_fetch() methods. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2013-11-06uprobes: Export write_opcode() as uprobe_write_opcode()Oleg Nesterov1-0/+1
set_swbp() and set_orig_insn() are __weak, but this is pointless because write_opcode() is static. Export write_opcode() as uprobe_write_opcode() for the upcoming arm port, this way it can actually override set_swbp() and use __opcode_to_mem_arm(bpinsn) instead if UPROBE_SWBP_INSN. Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-11-06uprobes: Move function declarations out of archDavid A. Long1-0/+8
Move the function declarations from the arch headers to the common header, since only the function bodies are architecture-specific. These changes are from Vincent Rabin's uprobes patch. [ oleg: update arch/powerpc/include/asm/uprobes.h ] Signed-off-by: Rabin Vincent <rabin@rab.in> Signed-off-by: David A. Long <dave.long@linaro.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-10-29uprobes: Teach uprobe_copy_process() to handle CLONE_VFORKOleg Nesterov1-2/+2
uprobe_copy_process() does nothing if the child shares ->mm with the forking process, but there is a special case: CLONE_VFORK. In this case it would be more correct to do dup_utask() but avoid dup_xol(). This is not that important, the child should not unwind its stack too much, this can corrupt the parent's stack, but at least we need this to allow to ret-probe __vfork() itself. Note: in theory, it would be better to check task_pt_regs(p)->sp instead of CLONE_VFORK, we need to dup_utask() if and only if the child can return from the function called by the parent. But this needs the arch-dependant helper, and I think that nobody actually does clone(same_stack, CLONE_VM). Reported-by: Martin Cermak <mcermak@redhat.com> Reported-by: David Smith <dsmith@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-10-29uprobes: Remove the wrong __weak attributeRalf Baechle1-1/+1
linux/uprobes.h declares arch_uprobe_skip_sstep() as a weak function. But as there is no definition of generic version so when trying to build uprobes for an architecture that doesn't yet have a arch_uprobe_skip_sstep() implementation, the vmlinux will try to call arch_uprobe_skip_sstep() somehwere in Stupidhistan leading to a system crash. We rather want a proper link error so remove arch_uprobe_skip_sstep(). Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-04-13uretprobes: Limit the depth of return probe nestednessAnton Arapov1-0/+3
Unlike the kretprobes we can't trust userspace, thus must have protection from user space attacks. User-space have "unlimited" stack, and this patch limits the return probes nestedness as a simple remedy for it. Note that this implementation leaks return_instance on siglongjmp until exit()/exec(). The intention is to have KISS and bare minimum solution for the initial implementation in order to not complicate the uretprobes code. In the future we may come up with more sophisticated solution that remove this depth limitation. It is not easy task and lays beyond this patchset. Signed-off-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-04-13uretprobes: Return probe entry, prepare_uretprobe()Anton Arapov1-0/+1
When a uprobe with return probe consumer is hit, prepare_uretprobe() function is invoked. It creates return_instance, hijacks return address and replaces it with the trampoline. * Return instances are kept as stack per uprobed task. * Return instance is chained, when the original return address is trampoline's page vaddr (e.g. recursive call of the probed function). Signed-off-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-04-13uretprobes: Introduce uprobe_consumer->ret_handler()Anton Arapov1-0/+3
Enclose return probes implementation, introduce ->ret_handler() and update existing code to rely on ->handler() *and* ->ret_handler() for uprobe and uretprobe respectively. Signed-off-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-04-04uprobes: Add trap variant helperAnanth N Mavinakayanahalli1-0/+1
Some architectures like powerpc have multiple variants of the trap instruction. Introduce an additional helper is_trap_insn() for run-time handling of non-uprobe traps on such architectures. While there, change is_swbp_at_addr() to is_trap_at_addr() for reading clarity. With this change, the uprobe registration path will supercede any trap instruction inserted at the requested location, while taking care of delivering the SIGTRAP for cases where the trap notification came in for an address without a uprobe. See [1] for a more detailed explanation. [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2013-March/104771.html This change was suggested by Oleg Nesterov. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-02-08uprobes: Introduce uprobe_apply()Oleg Nesterov1-0/+6
Currently it is not possible to change the filtering constraints after uprobe_register(), so a consumer can not, say, start to trace a task/mm which was previously filtered out, or remove the no longer needed bp's. Introduce uprobe_apply() which simply does register_for_each_vma() again to consult uprobe_consumer->filter() and install/remove the breakpoints. The only complication is that register_for_each_vma() can no longer assume that uprobe->consumers should be consulter if is_register == T, so we change it to accept "struct uprobe_consumer *new" instead. Unlike uprobe_register(), uprobe_apply(true) doesn't do "unregister" if register_for_each_vma() fails, it is up to caller to handle the error. Note: we probably need to cleanup the current interface, it is strange that uprobe_apply/unregister need inode/offset. We should either change uprobe_register() to return "struct uprobe *", or add a private ->uprobe member in uprobe_consumer. And in the long term uprobe_apply() should take a single argument, uprobe or consumer, even "bool add" should go away. Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2013-02-08uprobes: Teach handler_chain() to filter out the probed taskOleg Nesterov1-0/+3
Currrently the are 2 problems with pre-filtering: 1. It is not possible to add/remove a task (mm) after uprobe_register() 2. A forked child inherits all breakpoints and uprobe_consumer can not control this. This patch does the first step to improve the filtering. handler_chain() removes the breakpoints installed by this uprobe from current->mm if all handlers return UPROBE_HANDLER_REMOVE. Note that handler_chain() relies on ->register_rwsem to avoid the race with uprobe_register/unregister which can add/del a consumer, or even remove and then insert the new uprobe at the same address. Perhaps we will add uprobe_apply_mm(uprobe, mm, is_register) and teach copy_mm() to do filter(UPROBE_FILTER_FORK), but I think this change makes sense anyway. Note: instead of checking the retcode from uc->handler, we could add uc->filter(UPROBE_FILTER_BPHIT). But I think this is not optimal to call 2 hooks in a row. This buys nothing, and if handler/filter do something nontrivial they will probably do the same work twice. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2013-02-08uprobes: Reintroduce uprobe_consumer->filter()Oleg Nesterov1-0/+9
Finally add uprobe_consumer->filter() and change consumer_filter() to actually call this method. Note that ->filter() accepts mm_struct, not task_struct. Because: 1. We do not have for_each_mm_user(mm, task). 2. Even if we implement for_each_mm_user(), ->filter() can use it itself. 3. It is not clear who will actually need this interface to do the "nontrivial" filtering. Another argument is "enum uprobe_filter_ctx", consumer->filter() can use it to figure out why/where it was called. For example, perhaps we can add UPROBE_FILTER_PRE_REGISTER used by build_map_info() to quickly "nack" the unwanted mm's. In this case consumer should know that it is called under ->i_mmap_mutex. See the previous discussion at http://marc.info/?t=135214229700002 Perhaps we should pass more arguments, vma/vaddr? Note: this patch obviously can't help to filter out the child created by fork(), this will be addressed later. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2013-02-08uprobes: Kill uprobe_consumer->filter()Oleg Nesterov1-5/+0
uprobe_consumer->filter() is pointless in its current form, kill it. We will add it back, but with the different signature/semantics. Perhaps we will even re-introduce the callsite in handler_chain(), but not to just skip uc->handler(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-11-16uprobes: Use percpu_rw_semaphore to fix register/unregister vs dup_mmap() raceOleg Nesterov1-0/+8
This was always racy, but 268720903f87e0b84b161626c4447b81671b5d18 "uprobes: Rework register_for_each_vma() to make it O(n)" should be blamed anyway, it made everything worse and I didn't notice. register/unregister call build_map_info() and then do install/remove breakpoint for every mm which mmaps inode/offset. This can obviously race with fork()->dup_mmap() in between and we can miss the child. uprobe_register() could be easily fixed but unregister is much worse, the new mm inherits "int3" from parent and there is no way to detect this if uprobe goes away. So this patch simply adds percpu_down_read/up_read around dup_mmap(), and percpu_down_write/up_write into register_for_each_vma(). This adds 2 new hooks into dup_mmap() but we can kill uprobe_dup_mmap() and fold it into uprobe_end_dup_mmap(). Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
2012-11-03uprobes: Kill arch_uprobe_enable/disable_step() hooksOleg Nesterov1-2/+0
Kill arch_uprobe_enable/disable_step() hooks, they do nothing and nobody needs them. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-10-07uprobes: Introduce prepare_uprobe()Oleg Nesterov1-10/+0
Preparation. Extract the copy_insn/arch_uprobe_analyze_insn code from install_breakpoint() into the new helper, prepare_uprobe(). And move uprobe->flags defines from uprobes.h to uprobes.c, nobody else can use them anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-09-29uprobes: Kill UTASK_BP_HIT stateOleg Nesterov1-1/+0
Kill UTASK_BP_HIT state, it buys nothing but complicates the code. It is only used in uprobe_notify_resume() to decide who should be called, we can check utask->active_uprobe != NULL instead. And this allows us to simplify handle_swbp(), no need to clear utask->state. Likewise we could kill UTASK_SSTEP, but UTASK_BP_HIT is worse and imho should die. The problem is, it creates the special case when task->utask is NULL, we can't distinguish RUNNING and BP_HIT. With this patch utask == NULL always means RUNNING. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-09-15uprobes: Introduce arch_uprobe_enable/disable_step()Sebastian Andrzej Siewior1-0/+2
As Oleg pointed out in [0] uprobe should not use the ptrace interface for enabling/disabling single stepping. [0] http://lkml.kernel.org/r/20120730141638.GA5306@redhat.com Add the new "__weak arch" helpers which simply call user_*_single_step() as a preparation. This is only needed to not break the powerpc port, we will fold this logic into arch_uprobe_pre/post_xol() hooks later. We should also change handle_singlestep(), _disable_step(&uprobe->arch) should be called before put_uprobe(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-08-28uprobes: Remove "verify" argument from set_orig_insn()Oleg Nesterov1-1/+1
Nobody does set_orig_insn(verify => false), and I think nobody will. Remove this argument. IIUC set_orig_insn(verify => false) was needed to single-step without xol area. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-08-28uprobes: Fold uprobe_reset_state() into uprobe_dup_mmap()Oleg Nesterov1-4/+0
Now that we have uprobe_dup_mmap() we can fold uprobe_reset_state() into the new hook and remove it. mmput()->uprobe_clear_state() can't be called before dup_mmap(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-08-28uprobes: Introduce MMF_HAS_UPROBESOleg Nesterov1-0/+5
Add the new MMF_HAS_UPROBES flag. It is set by install_breakpoint() and it is copied by dup_mmap(), uprobe_pre_sstep_notifier() checks it to avoid the slow path if the task was never probed. Perhaps it makes sense to check it in valid_vma(is_register => false) as well. This needs the new dup_mmap()->uprobe_dup_mmap() hook. We can't use uprobe_reset_state() or put MMF_HAS_UPROBES into MMF_INIT_MASK, we need oldmm->mmap_sem to avoid the race with uprobe_register() or mmap() from another thread. Currently we never clear this bit, it can be false-positive after uprobe_unregister() or uprobe_munmap() or if dup_mmap() hits the probed VM_DONTCOPY vma. But this is fine correctness-wise and has no effect unless the task hits the non-uprobe breakpoint. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-08-28uprobes: Kill uprobes_state->countOleg Nesterov1-1/+1
uprobes_state->count is only needed to avoid the slow path in uprobe_pre_sstep_notifier(). It is also checked in uprobe_munmap() but ironically its only goal to decrement this counter. However, it is very broken. Just some examples: - uprobe_mmap() can race with uprobe_unregister() and wrongly increment the counter if it hits the non-uprobe "int3". Note that install_breakpoint() checks ->consumers first and returns -EEXIST if it is NULL. "atomic_sub() if error" in uprobe_mmap() looks obviously wrong too. - uprobe_munmap() can race with uprobe_register() and wrongly decrement the counter by the same reason. - Suppose an appication tries to increase the mmapped area via sys_mremap(). vma_adjust() does uprobe_munmap(whole_vma) first, this can nullify the counter temporarily and race with another thread which can hit the bp, the application will be killed by SIGTRAP. - Suppose an application mmaps 2 consecutive areas in the same file and one (or both) of these areas has uprobes. In the likely case mmap_region()->vma_merge() suceeds. Like above, this leads to uprobe_munmap/uprobe_mmap from vma_merge()->vma_adjust() but then mmap_region() does another uprobe_mmap(resulting_vma) and doubles the counter. This patch only removes this counter and fixes the compile errors, then we will try to cleanup the changed code and add something else instead. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-04-14uprobes/core: Decrement uprobe count before the pages are unmappedSrikar Dronamraju1-2/+3
Uprobes has a callback (uprobe_munmap()) in the unmap path to maintain the uprobes count. In the exit path this callback gets called in unlink_file_vma(). However by the time unlink_file_vma() is called, the pages would have been unmapped (in unmap_vmas()) and the task->rss_stat counts accounted (in zap_pte_range()). If the exiting process has probepoints, uprobe_munmap() checks if the breakpoint instruction was around before decrementing the probe count. This results in a file backed page being reread by uprobe_munmap() and hence it does not find the breakpoint. This patch fixes this problem by moving the callback to unmap_single_vma(). Since unmap_single_vma() may not unmap the complete vma, add start and end parameters to uprobe_munmap(). This bug became apparent courtesy of commit c3f0327f8e9d ("mm: add rss counters consistency check"). Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Anton Arapov <anton@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120411103527.23245.9835.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-31uprobes/core: Optimize probe hits with the help of a counterSrikar Dronamraju1-0/+5
Maintain a per-mm counter: number of uprobes that are inserted on this process address space. This counter can be used at probe hit time to determine if we need a lookup in the uprobes rbtree. Everytime a probe gets inserted successfully, the probe count is incremented and everytime a probe gets removed, the probe count is decremented. The new uprobe_munmap hook ensures the count is correct on a unmap or remap of a region. We expect that once a uprobe_munmap() is called, the vma goes away. So uprobe_unregister() finding a probe to unregister would either mean unmap event hasnt occurred yet or a mmap event on the same executable file occured after a unmap event. Additionally, uprobe_mmap hook now also gets called: a. on every executable vma that is COWed at fork. b. a vma of interest is newly mapped; breakpoint insertion also happens at the required address. On process creation, make sure the probes count in the child is set correctly. Special cases that are taken care include: a. mremap b. VM_DONTCOPY vmas on fork() c. insertion/removal races in the parent during fork(). Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Anton Arapov <anton@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120330182646.10018.85805.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-31uprobes/core: Allocate XOL slots for uprobes useSrikar Dronamraju1-0/+34
Uprobes executes the original instruction at a probed location out of line. For this, we allocate a page (per mm) upon the first uprobe hit, in the process user address space, divide it into slots that are used to store the actual instructions to be singlestepped. These slots are known as xol (execution out of line) slots. Care is taken to ensure that the allocation is in an unmapped area as close to the top of the user address space as possible, with appropriate permission settings to keep selinux like frameworks happy. Upon a uprobe hit, a free slot is acquired, and is released after the singlestep completes. Lots of improvements courtesy suggestions/inputs from Peter and Oleg. [ Folded a fix for build issue on powerpc fixed and reported by Stephen Rothwell. ] Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Anton Arapov <anton@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120330182631.10018.48175.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-03-14uprobes/core: Handle breakpoint and singlestep exceptionsSrikar Dronamraju1-3/+52
Uprobes uses exception notifiers to get to know if a thread hit a breakpoint or a singlestep exception. When a thread hits a uprobe or is singlestepping post a uprobe hit, the uprobe exception notifier sets its TIF_UPROBE bit, which will then be checked on its return to userspace path (do_notify_resume() ->uprobe_notify_resume()), where the consumers handlers are run (in task context) based on the defined filters. Uprobe hits are thread specific and hence we need to maintain information about if a task hit a uprobe, what uprobe was hit, the slot where the original instruction was copied for xol so that it can be singlestepped with appropriate fixups. In some cases, special care is needed for instructions that are executed out of line (xol). These are architecture specific artefacts, such as handling RIP relative instructions on x86_64. Since the instruction at which the uprobe was inserted is executed out of line, architecture specific fixups are added so that the thread continues normal execution in the presence of a uprobe. Postpone the signals until we execute the probed insn. post_xol() path does a recalc_sigpending() before return to user-mode, this ensures the signal can't be lost. Uprobes relies on DIE_DEBUG notification to notify if a singlestep is complete. Adds x86 specific uprobe exception notifiers and appropriate hooks needed to determine a uprobe hit and subsequent post processing. Add requisite x86 fixups for xol for uprobes. Specific cases needing fixups include relative jumps (x86_64), calls, etc. Where possible, we check and skip singlestepping the breakpointed instructions. For now we skip single byte as well as few multibyte nop instructions. However this can be extended to other instructions too. Credits to Oleg Nesterov for suggestions/patches related to signal, breakpoint, singlestep handling code. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120313180011.29771.89027.sendpatchset@srdronam.in.ibm.com [ Performed various cleanliness edits ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13uprobes/core: Rename bkpt to swbpSrikar Dronamraju1-2/+2
bkpt doesnt seem to be a correct abbrevation for breakpoint. Choice was between bp and breakpoint. Since bp can refer to things other than breakpoint, use swbp to refer to breakpoints. This is pure cleanup, no functional change intended. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120312092545.5379.91251.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13uprobes/core: Make order of function parameters consistent across functionsSrikar Dronamraju1-6/+6
If a function takes struct uprobe or struct arch_uprobe, then it is passed as the first parameter. This is pure cleanup, no functional change intended. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120312092530.5379.18394.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-03-13uprobes/core: Make macro names consistentSrikar Dronamraju1-2/+2
Rename macros that refer to individual uprobe to start with UPROBE_ instead of UPROBES_. This is pure cleanup, no functional change intended. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Linux-mm <linux-mm@kvack.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120312092514.5379.36595.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22uprobes: Update copyright noticesIngo Molnar1-1/+2
Add Peter Zijlstra's copyright to the uprobes code, whose contributions to the uprobes code are not visible in the Git history, because they were backmerged. Also update existing copyright notices to the year 2012. Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Link: http://lkml.kernel.org/n/tip-vjqxst502pc1efz7ah8cyht4@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22uprobes/core: Move insn to arch specific structureSrikar Dronamraju1-21/+2
Few cleanups suggested by Ingo Molnar. - Rename struct uprobe_arch_info to struct arch_uprobe. - Move insn from struct uprobe to struct arch_uprobe. - Make arch specific uprobe functions to accept struct arch_uprobe instead of struct uprobe. - Move struct uprobe to kernel/uprobes.c from include/linux/uprobes.h Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Stone <jistone@redhat.com> Link: http://lkml.kernel.org/r/20120222091602.15880.40249.sendpatchset@srdronam.in.ibm.com [ Made various small improvements ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22uprobes/core: Remove uprobe_opcode_szSrikar Dronamraju1-2/+0
uprobe_opcode_sz refers to the smallest instruction size for that architecture. UPROBES_BKPT_INSN_SIZE refers to the size of the breakpoint instruction for that architecture. For now we are assuming that both uprobe_opcode_sz and UPROBES_BKPT_INSN_SIZE are the same for all archs and hence removing uprobe_opcode_sz in favour of UPROBES_BKPT_INSN_SIZE. However if we have to support architectures where the smallest instruction size is different from the size of breakpoint instruction, we may have to re-introduce uprobe_opcode_sz. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Josh Stone <jistone@redhat.com> Link: http://lkml.kernel.org/r/20120222091549.15880.67020.sendpatchset@srdronam.in.ibm.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-17uprobes/core: Clean up, refactor and improve the codeIngo Molnar1-15/+13
Make the uprobes code readable to me: - improve the Kconfig text so that a mere mortal gets some idea what CONFIG_UPROBES=y is really about - do trivial renames to standardize around the uprobes_*() namespace - clean up and simplify various code flow details - separate basic blocks of functionality - line break artifact and white space related removal - use standard local varible definition blocks - use vertical spacing to make things more readable - remove unnecessary volatile - restructure comment blocks to make them more uniform and more readable in general Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Jim Keniston <jkenisto@us.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Link: http://lkml.kernel.org/n/tip-ewbwhb8o6navvllsauu7k07p@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-17uprobes, mm, x86: Add the ability to install and remove uprobes breakpointsSrikar Dronamraju1-0/+98
Add uprobes support to the core kernel, with x86 support. This commit adds the kernel facilities, the actual uprobes user-space ABI and perf probe support comes in later commits. General design: Uprobes are maintained in an rb-tree indexed by inode and offset (the offset here is from the start of the mapping). For a unique (inode, offset) tuple, there can be at most one uprobe in the rb-tree. Since the (inode, offset) tuple identifies a unique uprobe, more than one user may be interested in the same uprobe. This provides the ability to connect multiple 'consumers' to the same uprobe. Each consumer defines a handler and a filter (optional). The 'handler' is run every time the uprobe is hit, if it matches the 'filter' criteria. The first consumer of a uprobe causes the breakpoint to be inserted at the specified address and subsequent consumers are appended to this list. On subsequent probes, the consumer gets appended to the existing list of consumers. The breakpoint is removed when the last consumer unregisters. For all other unregisterations, the consumer is removed from the list of consumers. Given a inode, we get a list of the mms that have mapped the inode. Do the actual registration if mm maps the page where a probe needs to be inserted/removed. We use a temporary list to walk through the vmas that map the inode. - The number of maps that map the inode, is not known before we walk the rmap and keeps changing. - extending vm_area_struct wasn't recommended, it's a size-critical data structure. - There can be more than one maps of the inode in the same mm. We add callbacks to the mmap methods to keep an eye on text vmas that are of interest to uprobes. When a vma of interest is mapped, we insert the breakpoint at the right address. Uprobe works by replacing the instruction at the address defined by (inode, offset) with the arch specific breakpoint instruction. We save a copy of the original instruction at the uprobed address. This is needed for: a. executing the instruction out-of-line (xol). b. instruction analysis for any subsequent fixups. c. restoring the instruction back when the uprobe is unregistered. We insert or delete a breakpoint instruction, and this breakpoint instruction is assumed to be the smallest instruction available on the platform. For fixed size instruction platforms this is trivially true, for variable size instruction platforms the breakpoint instruction is typically the smallest (often a single byte). Writing the instruction is done by COWing the page and changing the instruction during the copy, this even though most platforms allow atomic writes of the breakpoint instruction. This also mirrors the behaviour of a ptrace() memory write to a PRIVATE file map. The core worker is derived from KSM's replace_page() logic. In essence, similar to KSM: a. allocate a new page and copy over contents of the page that has the uprobed vaddr b. modify the copy and insert the breakpoint at the required address c. switch the original page with the copy containing the breakpoint d. flush page tables. replace_page() is being replicated here because of some minor changes in the type of pages and also because Hugh Dickins had plans to improve replace_page() for KSM specific work. Instruction analysis on x86 is based on instruction decoder and determines if an instruction can be probed and determines the necessary fixups after singlestep. Instruction analysis is done at probe insertion time so that we avoid having to repeat the same analysis every time a probe is hit. A lot of code here is due to the improvement/suggestions/inputs from Peter Zijlstra. Changelog: (v10): - Add code to clear REX.B prefix as suggested by Denys Vlasenko and Masami Hiramatsu. (v9): - Use insn_offset_modrm as suggested by Masami Hiramatsu. (v7): Handle comments from Peter Zijlstra: - Dont take reference to inode. (expect inode to uprobe_register to be sane). - Use PTR_ERR to set the return value. - No need to take reference to inode. - use PTR_ERR to return error value. - register and uprobe_unregister share code. (v5): - Modified del_consumer as per comments from Peter. - Drop reference to inode before dropping reference to uprobe. - Use i_size_read(inode) instead of inode->i_size. - Ensure uprobe->consumers is NULL, before __uprobe_unregister() is called. - Includes errno.h as recommended by Stephen Rothwell to fix a build issue on sparc defconfig - Remove restrictions while unregistering. - Earlier code leaked inode references under some conditions while registering/unregistering. - Continue the vma-rmap walk even if the intermediate vma doesnt meet the requirements. - Validate the vma found by find_vma before inserting/removing the breakpoint - Call del_consumer under mutex_lock. - Use hash locks. - Handle mremap. - Introduce find_least_offset_node() instead of close match logic in find_uprobe - Uprobes no more depends on MM_OWNER; No reference to task_structs while inserting/removing a probe. - Uses read_mapping_page instead of grab_cache_page so that the pages have valid content. - pass NULL to get_user_pages for the task parameter. - call SetPageUptodate on the new page allocated in write_opcode. - fix leaking a reference to the new page under certain conditions. - Include Instruction Decoder if Uprobes gets defined. - Remove const attributes for instruction prefix arrays. - Uses mm_context to know if the application is 32 bit. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Also-written-by: Jim Keniston <jkenisto@us.ibm.com> Reviewed-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Roland McGrath <roland@hack.frob.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Anton Arapov <anton@redhat.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linux-mm <linux-mm@kvack.org> Link: http://lkml.kernel.org/r/20120209092642.GE16600@linux.vnet.ibm.com [ Made various small edits to the commit log ] Signed-off-by: Ingo Molnar <mingo@elte.hu>