From a5fd477ceb5f5c130a39d0415b3ea82c697b131a Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Thu, 2 Dec 2010 11:12:53 +0100
Subject: Also read ELF data sections

---
 elf.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 79 insertions(+), 5 deletions(-)

diff --git a/elf.c b/elf.c
index 439433b..eca6d9f 100644
--- a/elf.c
+++ b/elf.c
@@ -9,6 +9,7 @@
  */
 
 #include <stdio.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <libelf.h>
 #include <gelf.h>
@@ -23,11 +24,34 @@
  * http://elftoolchain.sourceforge.net/for-review/libelf-by-example-20100112.pdf
  */
 
+static bool elf_is_text_section(GElf_Shdr *shdr)
+{
+	if (shdr->sh_type == SHT_PROGBITS
+	    && (shdr->sh_flags & ~SHF_WRITE) == (SHF_ALLOC | SHF_EXECINSTR))
+		return true;
+	return false;
+}
+
+static bool elf_is_data_section(GElf_Shdr *shdr)
+{
+	if (shdr->sh_type == SHT_PROGBITS
+	    && (shdr->sh_flags & ~SHF_WRITE) == SHF_ALLOC)
+		return true;
+
+	if (shdr->sh_type == SHT_NOBITS
+	    && (shdr->sh_flags == (SHF_ALLOC | SHF_WRITE)))
+		return true;
+
+	return false;
+}
+
 static int elf_read_sections(Elf *e, struct memory *mem)
 {
 	Elf_Scn *scn = NULL;
 	size_t shstrndx;
 	char *name;
+	bool found_text = false;
+	bool found_data = false;
 
 	if (elf_getshdrstrndx(e, &shstrndx) != 0) {
 		err("elf_getshdrstrndx() failed: %s\n", elf_errmsg(-1));
@@ -36,7 +60,6 @@ static int elf_read_sections(Elf *e, struct memory *mem)
 
 	while ((scn = elf_nextscn(e, scn)) != NULL) {
 		GElf_Shdr shdr;
-		GElf_Phdr phdr;
 
 		if (gelf_getshdr(scn, &shdr) == NULL) {
 			err("Couldn't get section header: %s\n", elf_errmsg(-1));
@@ -44,8 +67,34 @@ static int elf_read_sections(Elf *e, struct memory *mem)
 		}
 
 		/* Is it a .text section? */
-		if (shdr.sh_type == SHT_PROGBITS
-		    && (shdr.sh_flags & ~SHF_WRITE) == (SHF_ALLOC | SHF_EXECINSTR)) {
+		if (elf_is_text_section(&shdr)) {
+			Elf_Data *text;
+			size_t n;
+
+			if ((name = elf_strptr(e, shstrndx, shdr.sh_name)) == NULL) {
+				err("Couldn't get section name: %s\n", elf_errmsg(-1));
+				return -1;
+			}
+
+			dbg("text section %zu: %s (size=%zu, flags=%08lx, addr=%08lx, off=%08lx)\n",
+					elf_ndxscn(scn), name, shdr.sh_size, shdr.sh_flags, shdr.sh_addr, shdr.sh_offset);
+
+			text = NULL;
+			n = 0;
+			while (n < shdr.sh_size &&
+					(text = elf_getdata(scn, text)) != NULL) {
+				if (shdr.sh_addr + n + text->d_size > mem->size) {
+					err("Would write behind memory\n");
+					return -1;
+				}
+
+				memcpy(&mem->base[(shdr.sh_addr + n) / 4], text->d_buf, text->d_size);
+
+				n += text->d_size;
+			}
+
+			found_text = true;
+		} else if (elf_is_data_section(&shdr)) {
 			Elf_Data *data;
 			size_t n;
 
@@ -54,19 +103,43 @@ static int elf_read_sections(Elf *e, struct memory *mem)
 				return -1;
 			}
 
-			dbg("Section %zu: %s (size=%zu, flags=%08lx, addr=%08lx, off=%08lx)\n", elf_ndxscn(scn), name, shdr.sh_size, shdr.sh_flags, shdr.sh_addr, shdr.sh_offset);
+			dbg("data section %zu: %s (size=%zu, flags=%08lx, addr=%08lx, off=%08lx)\n",
+					elf_ndxscn(scn), name, shdr.sh_size, shdr.sh_flags, shdr.sh_addr, shdr.sh_offset);
 
 			data = NULL;
 			n = 0;
 			while (n < shdr.sh_size &&
 					(data = elf_getdata(scn, data)) != NULL) {
+				if (shdr.sh_addr + n + data->d_size > mem->size) {
+					err("Would write behind memory\n");
+					return -1;
+				}
+
+				/* XXX: why could this ever be NULL? */
+				if (data->d_buf == NULL) {
+					err("data section %s is empty\n", name);
+					break;
+				}
+
 				memcpy(&mem->base[(shdr.sh_addr + n) / 4], data->d_buf, data->d_size);
 
 				n += data->d_size;
 			}
+
+			found_data = true;
 		}
 	}
 
+	if (!found_text) {
+		err("No text section found in binary\n");
+		return -1;
+	}
+
+	if (!found_data) {
+		err("No data section found in binary\n");
+		return -1;
+	}
+
 	return 0;
 }
 
@@ -76,7 +149,6 @@ int elf_load(FILE *fp, const char *name, struct memory *mem)
 	int ret;
 	Elf *e;
 	GElf_Ehdr ehdr;
-	size_t n;
 
 	if (unlikely(fd < 0)) {
 		err("Couldn't get file descriptor for '%s'\n", name);
@@ -95,6 +167,8 @@ int elf_load(FILE *fp, const char *name, struct memory *mem)
 		goto out;
 	}
 
+	/* Check whether we've got a valid ELF executable for Nios II */
+
 	if (elf_kind(e) != ELF_K_ELF) {
 		err("'%s' is not an ELF object\n", name);
 		goto out;
-- 
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