From b364d9538073716a256b37a790ff7bf3ddbb4f1b Mon Sep 17 00:00:00 2001
From: Dmitriy Ivanov <dimitry@google.com>
Date: Tue, 16 Sep 2014 14:31:06 -0700
Subject: [PATCH] Remove has_DT_SYMBOLIC flag
From the elf-spec: "Symbolically bound shared objects are
identified by the .dynamic entry DT_SYMBOLIC. This tag is
informational only; the runtime linker processes symbol
lookups from these objects in the same manner as any
other object."
Bug: 18186310
(cherry picked from commit 8f61d991831f0ea515fa50a5c38dbbcfbab0dd28)
Change-Id: I37024799ac8d1837993c8ae78780a448bedd6539
---
linker/dlfcn.cpp | 1 -
linker/linker.cpp | 131 ++++++++++++++--------------------------------
linker/linker.h | 2 +-
3 files changed, 40 insertions(+), 94 deletions(-)
diff --git a/linker/dlfcn.cpp b/linker/dlfcn.cpp
index 59f673ad5..c02bfb89a 100644
--- a/linker/dlfcn.cpp
+++ b/linker/dlfcn.cpp
@@ -244,7 +244,6 @@ soinfo* get_libdl_info() {
__libdl_info.nchain = sizeof(g_libdl_chains)/sizeof(unsigned);
__libdl_info.bucket = g_libdl_buckets;
__libdl_info.chain = g_libdl_chains;
- __libdl_info.has_DT_SYMBOLIC = true;
__libdl_info.ref_count = 1;
}
diff --git a/linker/linker.cpp b/linker/linker.cpp
index bd05498b0..246475b4e 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -487,117 +487,65 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi) {
ElfW(Sym)* s = nullptr;
if (somain != nullptr) {
- /*
- * Local scope is executable scope. Just start looking into it right away
- * for the shortcut.
- */
+ DEBUG("%s: looking up %s in executable %s",
+ si->name, name, somain->name);
- if (si == somain) {
- s = soinfo_elf_lookup(si, elf_hash, name);
- if (s != nullptr) {
- *lsi = si;
- goto done;
- }
+ // 1. Look for it in the main executable
+ s = soinfo_elf_lookup(somain, elf_hash, name);
+ if (s != nullptr) {
+ *lsi = somain;
+ }
- /* Next, look for it in the preloads list */
+ // 2. Look for it in the ld_preloads
+ if (s == nullptr) {
for (int i = 0; g_ld_preloads[i] != NULL; i++) {
s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
- if (s != NULL) {
- *lsi = g_ld_preloads[i];
- goto done;
- }
- }
- } else {
- /* Order of symbol lookup is controlled by DT_SYMBOLIC flag */
-
- /*
- * If this object was built with symbolic relocations disabled, the
- * first place to look to resolve external references is the main
- * executable.
- */
-
- if (!si->has_DT_SYMBOLIC) {
- DEBUG("%s: looking up %s in executable %s",
- si->name, name, somain->name);
- s = soinfo_elf_lookup(somain, elf_hash, name);
if (s != nullptr) {
- *lsi = somain;
- goto done;
- }
-
- /* Next, look for it in the preloads list */
- for (int i = 0; g_ld_preloads[i] != NULL; i++) {
- s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
- if (s != NULL) {
- *lsi = g_ld_preloads[i];
- goto done;
- }
+ *lsi = g_ld_preloads[i];
+ break;
}
}
+ }
- /* Look for symbols in the local scope (the object who is
- * searching). This happens with C++ templates on x86 for some
- * reason.
- *
- * Notes on weak symbols:
- * The ELF specs are ambiguous 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. */
+ /* Look for symbols in the local scope (the object who is
+ * searching). This happens with C++ templates on x86 for some
+ * reason.
+ *
+ * Notes on weak symbols:
+ * The ELF specs are ambiguous 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. */
+ if (s == nullptr) {
s = soinfo_elf_lookup(si, elf_hash, name);
if (s != nullptr) {
*lsi = si;
- goto done;
- }
-
- /*
- * If this object was built with -Bsymbolic and symbol is not found
- * in the local scope, try to find the symbol in the main executable.
- */
-
- if (si->has_DT_SYMBOLIC) {
- DEBUG("%s: looking up %s in executable %s after local scope",
- si->name, name, somain->name);
- s = soinfo_elf_lookup(somain, elf_hash, name);
- if (s != nullptr) {
- *lsi = somain;
- goto done;
- }
-
- /* Next, look for it in the preloads list */
- for (int i = 0; g_ld_preloads[i] != NULL; i++) {
- s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
- if (s != NULL) {
- *lsi = g_ld_preloads[i];
- goto done;
- }
- }
}
}
}
- si->get_children().visit([&](soinfo* child) {
- DEBUG("%s: looking up %s in %s", si->name, name, child->name);
- s = soinfo_elf_lookup(child, elf_hash, name);
- if (s != nullptr) {
- *lsi = child;
- return false;
- }
- return true;
- });
+ if (s == nullptr) {
+ si->get_children().visit([&](soinfo* child) {
+ DEBUG("%s: looking up %s in %s", si->name, name, child->name);
+ s = soinfo_elf_lookup(child, elf_hash, name);
+ if (s != nullptr) {
+ *lsi = child;
+ return false;
+ }
+ return true;
+ });
+ }
-done:
if (s != nullptr) {
TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
"found in %s, base = %p, load bias = %p",
si->name, name, reinterpret_cast<void*>(s->st_value),
(*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
reinterpret_cast<void*>((*lsi)->load_bias));
- return s;
}
- return nullptr;
+ return s;
}
// Each size has it's own allocator.
@@ -2042,7 +1990,7 @@ bool soinfo::PrelinkImage() {
break;
#endif
case DT_SYMBOLIC:
- has_DT_SYMBOLIC = true;
+ // ignored
break;
case DT_NEEDED:
++needed_count;
@@ -2056,9 +2004,6 @@ bool soinfo::PrelinkImage() {
has_text_relocations = true;
#endif
}
- if (d->d_un.d_val & DF_SYMBOLIC) {
- has_DT_SYMBOLIC = true;
- }
break;
#if defined(__mips__)
case DT_STRSZ:
@@ -2092,8 +2037,10 @@ bool soinfo::PrelinkImage() {
#endif
default:
- DEBUG("Unused DT entry: type %p arg %p",
- reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
+ if (!relocating_linker) {
+ DL_WARN("%s: unused DT entry: type %p arg %p", name,
+ reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
+ }
break;
}
}
diff --git a/linker/linker.h b/linker/linker.h
index ef2fbcd6c..e39585006 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -197,7 +197,7 @@ struct soinfo {
#if !defined(__LP64__)
bool has_text_relocations;
#endif
- bool has_DT_SYMBOLIC;
+ bool unused4; // DO NOT USE, maintained for compatibility
soinfo(const char* name, const struct stat* file_stat, off64_t file_offset, int rtld_flags);