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-rw-r--r--linker/linker.c156
1 files changed, 99 insertions, 57 deletions
diff --git a/linker/linker.c b/linker/linker.c
index 8dde941..e1f2792 100644
--- a/linker/linker.c
+++ b/linker/linker.c
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2008 The Android Open Source Project
+ * Copyright (C) 2008, 2009 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -48,6 +48,7 @@
#include "linker.h"
#include "linker_debug.h"
+#include "linker_format.h"
#include "ba.h"
@@ -71,7 +72,6 @@
*
* open issues / todo:
*
- * - should we do anything special for STB_WEAK symbols?
* - are we doing everything we should for ARM_COPY relocations?
* - cleaner error reporting
* - after linking, set as much stuff as possible to READONLY
@@ -95,15 +95,15 @@ static soinfo *somain; /* main process, always the one after libdl_info */
#endif
-/* Set up for the buddy allocator managing the prelinked libraries. */
-static struct ba_bits ba_prelink_bitmap[(LIBLAST - LIBBASE) / LIBINC];
-static struct ba ba_prelink = {
+/* Set up for the buddy allocator managing the non-prelinked libraries. */
+static struct ba_bits ba_nonprelink_bitmap[(LIBLAST - LIBBASE) / LIBINC];
+static struct ba ba_nonprelink = {
.base = LIBBASE,
.size = LIBLAST - LIBBASE,
.min_alloc = LIBINC,
/* max_order will be determined automatically */
- .bitmap = ba_prelink_bitmap,
- .num_entries = sizeof(ba_prelink_bitmap)/sizeof(ba_prelink_bitmap[0]),
+ .bitmap = ba_nonprelink_bitmap,
+ .num_entries = sizeof(ba_nonprelink_bitmap)/sizeof(ba_nonprelink_bitmap[0]),
};
static inline int validate_soinfo(soinfo *si)
@@ -151,7 +151,7 @@ static char tmp_err_buf[768];
static char __linker_dl_err_buf[768];
#define DL_ERR(fmt, x...) \
do { \
- snprintf(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), \
+ format_buffer(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), \
"%s[%d]: " fmt, __func__, __LINE__, ##x); \
ERROR(fmt "\n", ##x); \
} while(0)
@@ -266,7 +266,7 @@ static soinfo *alloc_info(const char *name)
if(strlen(name) >= SOINFO_NAME_LEN) {
DL_ERR("%5d library name %s too long", pid, name);
- return 0;
+ return NULL;
}
/* The freelist is populated when we call free_info(), which in turn is
@@ -414,20 +414,20 @@ static Elf32_Sym *_elf_lookup(soinfo *si, unsigned hash, const char *name)
s = symtab + n;
if(strcmp(strtab + s->st_name, name)) continue;
- /* only concern ourselves with global symbols */
+ /* only concern ourselves with global and weak symbol definitions */
switch(ELF32_ST_BIND(s->st_info)){
case STB_GLOBAL:
+ case STB_WEAK:
/* no section == undefined */
if(s->st_shndx == 0) continue;
- case STB_WEAK:
TRACE_TYPE(LOOKUP, "%5d FOUND %s in %s (%08x) %d\n", pid,
name, si->name, s->st_value, s->st_size);
return s;
}
}
- return 0;
+ return NULL;
}
static unsigned elfhash(const char *_name)
@@ -445,17 +445,9 @@ static unsigned elfhash(const char *_name)
}
static Elf32_Sym *
-_do_lookup_in_so(soinfo *si, const char *name, unsigned *elf_hash)
-{
- if (*elf_hash == 0)
- *elf_hash = elfhash(name);
- return _elf_lookup (si, *elf_hash, name);
-}
-
-static Elf32_Sym *
_do_lookup(soinfo *si, const char *name, unsigned *base)
{
- unsigned elf_hash = 0;
+ unsigned elf_hash = elfhash(name);
Elf32_Sym *s;
unsigned *d;
soinfo *lsi = si;
@@ -463,8 +455,14 @@ _do_lookup(soinfo *si, const char *name, unsigned *base)
/* Look for symbols in the local scope first (the object who is
* searching). This happens with C++ templates on i386 for some
- * reason. */
- s = _do_lookup_in_so(si, name, &elf_hash);
+ * reason.
+ *
+ * Notes on weak symbols:
+ * The ELF specs are ambigious about treatment of weak definitions in
+ * dynamic linking. Some systems return the first definition found
+ * and some the first non-weak definition. This is system dependent.
+ * Here we return the first definition found for simplicity. */
+ s = _elf_lookup(si, elf_hash, name);
if(s != NULL)
goto done;
@@ -482,12 +480,12 @@ _do_lookup(soinfo *si, const char *name, unsigned *base)
if (!validate_soinfo(lsi)) {
DL_ERR("%5d bad DT_NEEDED pointer in %s",
pid, si->name);
- return 0;
+ return NULL;
}
DEBUG("%5d %s: looking up %s in %s\n",
pid, si->name, name, lsi->name);
- s = _do_lookup_in_so(lsi, name, &elf_hash);
+ s = _elf_lookup(lsi, elf_hash, name);
if ((s != NULL) && (s->st_shndx != SHN_UNDEF))
goto done;
}
@@ -502,7 +500,7 @@ _do_lookup(soinfo *si, const char *name, unsigned *base)
lsi = somain;
DEBUG("%5d %s: looking up %s in executable %s\n",
pid, si->name, name, lsi->name);
- s = _do_lookup_in_so(lsi, name, &elf_hash);
+ s = _elf_lookup(lsi, elf_hash, name);
}
#endif
@@ -515,7 +513,7 @@ done:
return s;
}
- return 0;
+ return NULL;
}
/* This is used by dl_sym(). It performs symbol lookup only within the
@@ -523,15 +521,14 @@ done:
*/
Elf32_Sym *lookup_in_library(soinfo *si, const char *name)
{
- unsigned unused = 0;
- return _do_lookup_in_so(si, name, &unused);
+ return _elf_lookup(si, elfhash(name), name);
}
/* This is used by dl_sym(). It performs a global symbol lookup.
*/
Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start)
{
- unsigned elf_hash = 0;
+ unsigned elf_hash = elfhash(name);
Elf32_Sym *s = NULL;
soinfo *si;
@@ -543,7 +540,7 @@ Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start)
{
if(si->flags & FLAG_ERROR)
continue;
- s = _do_lookup_in_so(si, name, &elf_hash);
+ s = _elf_lookup(si, elf_hash, name);
if (s != NULL) {
*found = si;
break;
@@ -556,7 +553,7 @@ Elf32_Sym *lookup(const char *name, soinfo **found, soinfo *start)
return s;
}
- return 0;
+ return NULL;
}
soinfo *find_containing_library(void *addr)
@@ -643,7 +640,7 @@ static int open_library(const char *name)
return fd;
for (path = ldpaths; *path; path++) {
- n = snprintf(buf, sizeof(buf), "%s/%s", *path, name);
+ n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name);
if (n < 0 || n >= (int)sizeof(buf)) {
WARN("Ignoring very long library path: %s/%s\n", *path, name);
continue;
@@ -652,7 +649,7 @@ static int open_library(const char *name)
return fd;
}
for (path = sopaths; *path; path++) {
- n = snprintf(buf, sizeof(buf), "%s/%s", *path, name);
+ n = format_buffer(buf, sizeof(buf), "%s/%s", *path, name);
if (n < 0 || n >= (int)sizeof(buf)) {
WARN("Ignoring very long library path: %s/%s\n", *path, name);
continue;
@@ -851,14 +848,14 @@ alloc_mem_region(soinfo *si)
for it from the buddy allocator, which manages the area between
LIBBASE and LIBLAST.
*/
- si->ba_index = ba_allocate(&ba_prelink, si->size);
+ si->ba_index = ba_allocate(&ba_nonprelink, si->size);
if(si->ba_index >= 0) {
- si->base = ba_start_addr(&ba_prelink, si->ba_index);
+ si->base = ba_start_addr(&ba_nonprelink, si->ba_index);
PRINT("%5d mapping library '%s' at %08x (index %d) " \
"through buddy allocator.\n",
pid, si->name, si->base, si->ba_index);
if (reserve_mem_region(si) < 0) {
- ba_free(&ba_prelink, si->ba_index);
+ ba_free(&ba_nonprelink, si->ba_index);
si->ba_index = -1;
si->base = 0;
goto err;
@@ -1154,7 +1151,7 @@ load_library(const char *name)
/* Now actually load the library's segments into right places in memory */
if (load_segments(fd, &__header[0], si) < 0) {
if (si->ba_index >= 0) {
- ba_free(&ba_prelink, si->ba_index);
+ ba_free(&ba_nonprelink, si->ba_index);
si->ba_index = -1;
}
goto fail;
@@ -1257,7 +1254,7 @@ unsigned unload_library(soinfo *si)
PRINT("%5d releasing library '%s' address space at %08x "\
"through buddy allocator.\n",
pid, si->name, si->base);
- ba_free(&ba_prelink, si->ba_index);
+ ba_free(&ba_nonprelink, si->ba_index);
}
notify_gdb_of_unload(si);
free_info(si);
@@ -1296,10 +1293,64 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count)
if(sym != 0) {
sym_name = (char *)(strtab + symtab[sym].st_name);
s = _do_lookup(si, sym_name, &base);
- if(s == 0) {
- DL_ERR("%5d cannot locate '%s'...", pid, sym_name);
- return -1;
- }
+ if(s == NULL) {
+ /* We only allow an undefined symbol if this is a weak
+ reference.. */
+ s = &symtab[sym];
+ if (ELF32_ST_BIND(s->st_info) != STB_WEAK) {
+ DL_ERR("%5d cannot locate '%s'...\n", pid, sym_name);
+ return -1;
+ }
+
+ /* IHI0044C AAELF 4.5.1.1:
+
+ Libraries are not searched to resolve weak references.
+ It is not an error for a weak reference to remain
+ unsatisfied.
+
+ During linking, the value of an undefined weak reference is:
+ - Zero if the relocation type is absolute
+ - The address of the place if the relocation is pc-relative
+ - The address of nominial base address if the relocation
+ type is base-relative.
+ */
+
+ switch (type) {
+#if defined(ANDROID_ARM_LINKER)
+ case R_ARM_JUMP_SLOT:
+ case R_ARM_GLOB_DAT:
+ case R_ARM_ABS32:
+ case R_ARM_RELATIVE: /* Don't care. */
+ case R_ARM_NONE: /* Don't care. */
+#elif defined(ANDROID_X86_LINKER)
+ case R_386_JUMP_SLOT:
+ case R_386_GLOB_DAT:
+ case R_386_32:
+ case R_386_RELATIVE: /* Dont' care. */
+#endif /* ANDROID_*_LINKER */
+ /* sym_addr was initialized to be zero above or relocation
+ code below does not care about value of sym_addr.
+ No need to do anything. */
+ break;
+
+#if defined(ANDROID_X86_LINKER)
+ case R_386_PC32:
+ sym_addr = reloc;
+ break;
+#endif /* ANDROID_X86_LINKER */
+
+#if defined(ANDROID_ARM_LINKER)
+ case R_ARM_COPY:
+ /* Fall through. Can't really copy if weak symbol is
+ not found in run-time. */
+#endif /* ANDROID_ARM_LINKER */
+ default:
+ DL_ERR("%5d unknown weak reloc type %d @ %p (%d)\n",
+ pid, type, rel, (int) (rel - start));
+ return -1;
+ }
+ } else {
+ /* We got a definition. */
#if 0
if((base == 0) && (si->base != 0)){
/* linking from libraries to main image is bad */
@@ -1308,20 +1359,11 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count)
return -1;
}
#endif
- // st_shndx==SHN_UNDEF means an undefined symbol.
- // st_value should be 0 then, except that the low bit of st_value is
- // used to indicate whether the symbol points to an ARM or thumb function,
- // and should be ignored in the following check.
- if ((s->st_shndx == SHN_UNDEF) && ((s->st_value & ~1) != 0)) {
- DL_ERR("%5d In '%s', symbol=%s shndx=%d && value=0x%08x. We do not "
- "handle this yet", pid, si->name, sym_name, s->st_shndx,
- s->st_value);
- return -1;
- }
- sym_addr = (unsigned)(s->st_value + base);
+ sym_addr = (unsigned)(s->st_value + base);
+ }
COUNT_RELOC(RELOC_SYMBOL);
} else {
- s = 0;
+ s = NULL;
}
/* TODO: This is ugly. Split up the relocations by arch into
@@ -1988,7 +2030,7 @@ static int link_image(soinfo *si, unsigned wr_offset)
return 0;
fail:
- ERROR("failed to link %s\n", si->name);
+ DL_ERR("failed to link %s\n", si->name);
si->flags |= FLAG_ERROR;
return -1;
}
@@ -2145,7 +2187,7 @@ unsigned __linker_init(unsigned **elfdata)
vecs += 2;
}
- ba_init(&ba_prelink);
+ ba_init(&ba_nonprelink);
si->base = 0;
si->dynamic = (unsigned *)-1;
generated by cgit v1.1 at 2025-11-28 07:03:56 +0000