[PATCH 2/6] x86: relocs: consolidate processing logic
From: Kees Cook
Date: Fri Apr 12 2013 - 16:14:52 EST
Instead of counting and then processing relocations, do it in a single
pass. This splits the processing logic into separate functions for
realmode and 32-bit (and paves the way for 64-bit). Also extracts helper
functions when emitting relocations.
Based on work by Neill Clift and Michael Davidson.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/x86/tools/relocs.c | 304 ++++++++++++++++++++++++++---------------------
1 file changed, 170 insertions(+), 134 deletions(-)
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index fd28ef7..bdc5930 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -2,6 +2,7 @@
#include <stdarg.h>
#include <stdlib.h>
#include <stdint.h>
+#include <inttypes.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
@@ -38,10 +39,15 @@ static void die(char *fmt, ...);
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
static Elf_Ehdr ehdr;
-static unsigned long reloc_count, reloc_idx;
-static unsigned long *relocs;
-static unsigned long reloc16_count, reloc16_idx;
-static unsigned long *relocs16;
+
+struct relocs {
+ uint32_t *offset;
+ unsigned long count;
+ unsigned long size;
+};
+
+static struct relocs relocs16;
+static struct relocs relocs32;
struct section {
Elf_Shdr shdr;
@@ -583,8 +589,23 @@ static void print_absolute_relocs(void)
printf("\n");
}
-static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym),
- int use_real_mode)
+static void add_reloc(struct relocs *r, uint32_t offset)
+{
+ if (r->count == r->size) {
+ unsigned long newsize = r->size + 50000;
+ void *mem = realloc(r->offset, newsize * sizeof(r->offset[0]));
+
+ if (!mem)
+ die("realloc of %ld entries for relocs failed\n",
+ newsize);
+ r->offset = mem;
+ r->size = newsize;
+ }
+ r->offset[r->count++] = offset;
+}
+
+static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel,
+ Elf_Sym *sym, const char *symname))
{
int i;
/* Walk through the relocations */
@@ -606,100 +627,142 @@ static void walk_relocs(void (*visit)(Elf_Rel *rel, Elf_Sym *sym),
sh_symtab = sec_symtab->symtab;
sym_strtab = sec_symtab->link->strtab;
for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) {
- Elf_Rel *rel;
- Elf_Sym *sym;
- unsigned r_type;
- const char *symname;
- int shn_abs;
+ Elf_Rel *rel = &sec->reltab[j];
+ Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
+ const char *symname = sym_name(sym_strtab, sym);
- rel = &sec->reltab[j];
- sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
- r_type = ELF_R_TYPE(rel->r_info);
-
- shn_abs = sym->st_shndx == SHN_ABS;
-
- switch (r_type) {
- case R_386_NONE:
- case R_386_PC32:
- case R_386_PC16:
- case R_386_PC8:
- /*
- * NONE can be ignored and and PC relative
- * relocations don't need to be adjusted.
- */
+ process(sec, rel, sym, symname);
+ }
+ }
+}
+
+static int do_reloc(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
+ const char *symname)
+{
+ unsigned r_type = ELF32_R_TYPE(rel->r_info);
+ int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
+
+ switch (r_type) {
+ case R_386_NONE:
+ case R_386_PC32:
+ case R_386_PC16:
+ case R_386_PC8:
+ /*
+ * NONE can be ignored and PC relative relocations don't
+ * need to be adjusted.
+ */
+ break;
+
+ case R_386_32:
+ if (shn_abs) {
+ /*
+ * Whitelisted absolute symbols do not require
+ * relocation.
+ */
+ if (is_reloc(S_ABS, symname))
break;
- case R_386_16:
- symname = sym_name(sym_strtab, sym);
- if (!use_real_mode)
- goto bad;
- if (shn_abs) {
- if (is_reloc(S_ABS, symname))
- break;
- else if (!is_reloc(S_SEG, symname))
- goto bad;
- } else {
- if (is_reloc(S_LIN, symname))
- goto bad;
- else
- break;
- }
- visit(rel, sym);
+ die("Invalid absolute %s relocation: %s\n",
+ rel_type(r_type), symname);
+ break;
+ }
+
+ add_reloc(&relocs32, rel->r_offset);
+ break;
+
+ default:
+ die("Unsupported relocation type: %s (%d)\n",
+ rel_type(r_type), r_type);
+ break;
+ }
+
+ return 0;
+}
+
+static int do_reloc_real(struct section *sec, Elf_Rel *rel, Elf_Sym *sym,
+ const char *symname)
+{
+ unsigned r_type = ELF32_R_TYPE(rel->r_info);
+ int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname);
+
+ switch (r_type) {
+ case R_386_NONE:
+ case R_386_PC32:
+ case R_386_PC16:
+ case R_386_PC8:
+ /*
+ * NONE can be ignored and PC relative relocations don't
+ * need to be adjusted.
+ */
+ break;
+
+ case R_386_16:
+ if (shn_abs) {
+ /*
+ * Whitelisted absolute symbols do not require
+ * relocation.
+ */
+ if (is_reloc(S_ABS, symname))
break;
- case R_386_32:
- symname = sym_name(sym_strtab, sym);
- if (shn_abs) {
- if (is_reloc(S_ABS, symname))
- break;
- else if (!is_reloc(S_REL, symname))
- goto bad;
- } else {
- if (use_real_mode &&
- !is_reloc(S_LIN, symname))
- break;
- }
- visit(rel, sym);
+ if (is_reloc(S_SEG, symname)) {
+ add_reloc(&relocs16, rel->r_offset);
+ break;
+ }
+ } else {
+ if (!is_reloc(S_LIN, symname))
break;
- default:
- die("Unsupported relocation type: %s (%d)\n",
- rel_type(r_type), r_type);
+ }
+ die("Invalid %s %s relocation: %s\n",
+ shn_abs ? "absolute" : "relative",
+ rel_type(r_type), symname);
+ break;
+
+ case R_386_32:
+ if (shn_abs) {
+ /*
+ * Whitelisted absolute symbols do not require
+ * relocation.
+ */
+ if (is_reloc(S_ABS, symname))
+ break;
+
+ if (is_reloc(S_REL, symname)) {
+ add_reloc(&relocs32, rel->r_offset);
break;
- bad:
- symname = sym_name(sym_strtab, sym);
- die("Invalid %s %s relocation: %s\n",
- shn_abs ? "absolute" : "relative",
- rel_type(r_type), symname);
}
+ } else {
+ if (is_reloc(S_LIN, symname))
+ add_reloc(&relocs32, rel->r_offset);
+ break;
}
- }
-}
+ die("Invalid %s %s relocation: %s\n",
+ shn_abs ? "absolute" : "relative",
+ rel_type(r_type), symname);
+ break;
-static void count_reloc(Elf_Rel *rel, Elf_Sym *sym)
-{
- if (ELF_R_TYPE(rel->r_info) == R_386_16)
- reloc16_count++;
- else
- reloc_count++;
-}
+ default:
+ die("Unsupported relocation type: %s (%d)\n",
+ rel_type(r_type), r_type);
+ break;
+ }
-static void collect_reloc(Elf_Rel *rel, Elf_Sym *sym)
-{
- /* Remember the address that needs to be adjusted. */
- if (ELF_R_TYPE(rel->r_info) == R_386_16)
- relocs16[reloc16_idx++] = rel->r_offset;
- else
- relocs[reloc_idx++] = rel->r_offset;
+ return 0;
}
static int cmp_relocs(const void *va, const void *vb)
{
- const unsigned long *a, *b;
+ const uint32_t *a, *b;
a = va; b = vb;
return (*a == *b)? 0 : (*a > *b)? 1 : -1;
}
-static int write32(unsigned int v, FILE *f)
+static void sort_relocs(struct relocs *r)
+{
+ qsort(r->offset, r->count, sizeof(r->offset[0]), cmp_relocs);
+}
+
+static int write32(uint32_t v, FILE *f)
{
unsigned char buf[4];
@@ -707,33 +770,25 @@ static int write32(unsigned int v, FILE *f)
return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;
}
+static int write32_as_text(uint32_t v, FILE *f)
+{
+ return fprintf(f, "\t.long 0x%08"PRIx32"\n", v) > 0 ? 0 : -1;
+}
+
static void emit_relocs(int as_text, int use_real_mode)
{
int i;
- /* Count how many relocations I have and allocate space for them. */
- reloc_count = 0;
- walk_relocs(count_reloc, use_real_mode);
- relocs = malloc(reloc_count * sizeof(relocs[0]));
- if (!relocs) {
- die("malloc of %d entries for relocs failed\n",
- reloc_count);
- }
+ int (*write_reloc)(uint32_t, FILE *) = write32;
- relocs16 = malloc(reloc16_count * sizeof(relocs[0]));
- if (!relocs16) {
- die("malloc of %d entries for relocs16 failed\n",
- reloc16_count);
- }
/* Collect up the relocations */
- reloc_idx = 0;
- walk_relocs(collect_reloc, use_real_mode);
+ walk_relocs(use_real_mode ? do_reloc_real : do_reloc);
- if (reloc16_count && !use_real_mode)
+ if (relocs16.count && !use_real_mode)
die("Segment relocations found but --realmode not specified\n");
/* Order the relocations for more efficient processing */
- qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
- qsort(relocs16, reloc16_count, sizeof(relocs16[0]), cmp_relocs);
+ sort_relocs(&relocs16);
+ sort_relocs(&relocs32);
/* Print the relocations */
if (as_text) {
@@ -742,43 +797,24 @@ static void emit_relocs(int as_text, int use_real_mode)
*/
printf(".section \".data.reloc\",\"a\"\n");
printf(".balign 4\n");
- if (use_real_mode) {
- printf("\t.long %lu\n", reloc16_count);
- for (i = 0; i < reloc16_count; i++)
- printf("\t.long 0x%08lx\n", relocs16[i]);
- printf("\t.long %lu\n", reloc_count);
- for (i = 0; i < reloc_count; i++) {
- printf("\t.long 0x%08lx\n", relocs[i]);
- }
- } else {
- /* Print a stop */
- printf("\t.long 0x%08lx\n", (unsigned long)0);
- for (i = 0; i < reloc_count; i++) {
- printf("\t.long 0x%08lx\n", relocs[i]);
- }
- }
-
- printf("\n");
+ write_reloc = write32_as_text;
}
- else {
- if (use_real_mode) {
- write32(reloc16_count, stdout);
- for (i = 0; i < reloc16_count; i++)
- write32(relocs16[i], stdout);
- write32(reloc_count, stdout);
-
- /* Now print each relocation */
- for (i = 0; i < reloc_count; i++)
- write32(relocs[i], stdout);
- } else {
- /* Print a stop */
- write32(0, stdout);
- /* Now print each relocation */
- for (i = 0; i < reloc_count; i++) {
- write32(relocs[i], stdout);
- }
- }
+ if (use_real_mode) {
+ write_reloc(relocs16.count, stdout);
+ for (i = 0; i < relocs16.count; i++)
+ write_reloc(relocs16.offset[i], stdout);
+
+ write_reloc(relocs32.count, stdout);
+ for (i = 0; i < relocs32.count; i++)
+ write_reloc(relocs32.offset[i], stdout);
+ } else {
+ /* Print a stop */
+ write_reloc(0, stdout);
+
+ /* Now print each relocation */
+ for (i = 0; i < relocs32.count; i++)
+ write_reloc(relocs32.offset[i], stdout);
}
}
--
1.7.9.5
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