bpf: enable verifier to add 0 to packet ptr

The patch fixes the case when adding a zero value to the packet
pointer.  The zero value could come from src_reg equals type
BPF_K or CONST_IMM.  The patch fixes both, otherwise the verifer
reports the following error:
  [...]
    R0=imm0,min_value=0,max_value=0
    R1=pkt(id=0,off=0,r=4)
    R2=pkt_end R3=fp-12
    R4=imm4,min_value=4,max_value=4
    R5=pkt(id=0,off=4,r=4)
  269: (bf) r2 = r0     // r2 becomes imm0
  270: (77) r2 >>= 3
  271: (bf) r4 = r1     // r4 becomes pkt ptr
  272: (0f) r4 += r2    // r4 += 0
  addition of negative constant to packet pointer is not allowed

Signed-off-by: William Tu <u9012063@gmail.com>
Signed-off-by: Mihai Budiu <mbudiu@vmware.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c

path: root/tools/perf/trace/beauty/waitid_options.c

#include <sys/types.h>
#include <sys/wait.h>

static size_t syscall_arg__scnprintf_waitid_options(char *bf, size_t size,
						    struct syscall_arg *arg)
{
	int printed = 0, options = arg->val;

#define	P_OPTION(n) \
	if (options & W##n) { \
		printed += scnprintf(bf + printed, size - printed, "%s%s", printed ? "|" : "", #n); \
		options &= ~W##n; \
	}

	P_OPTION(NOHANG);
	P_OPTION(UNTRACED);
	P_OPTION(CONTINUED);
#undef P_OPTION

	if (options)
		printed += scnprintf(bf + printed, size - printed, "%s%#x", printed ? "|" : "", options);

	return printed;
}

#define SCA_WAITID_OPTIONS syscall_arg__scnprintf_waitid_options