Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
selftests/vDSO: support DT_GNU_HASH
glibc added support for DT_GNU_HASH in 2006 and DT_HASH has been
obsoleted for more than one decade in many Linux distributions.
Many vDSOs support DT_GNU_HASH. This patch adds selftests support.
Link: https://lore.kernel.org/r/20241206130724.7944-2-xry111@xry111.site
Signed-off-by: Fangrui Song <i@maskray.me>
Tested-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Xi Ruoyao <xry111@xry111.site> # rebase
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
authored by
Fangrui Song
and committed by
Shuah Khan
e0746bde
eed8ecdf
+80
-26
+80
-26
tools/testing/selftests/vDSO/parse_vdso.c
+80
-26
tools/testing/selftests/vDSO/parse_vdso.c
···
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/* Symbol table */
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ELF(Sym) *symtab;
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const char *symstrings;
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+
ELF(Word) *gnu_hash;
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ELF_HASH_ENTRY *bucket, *chain;
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ELF_HASH_ENTRY nbucket, nchain;
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···
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h ^= g >> 24;
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h &= ~g;
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}
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return h;
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}
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+
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static uint32_t gnu_hash(const char *name)
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{
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const unsigned char *s = (void *)name;
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uint32_t h = 5381;
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+
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for (; *s; s++)
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h += h * 32 + *s;
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return h;
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}
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···
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*/
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ELF_HASH_ENTRY *hash = 0;
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vdso_info.symstrings = 0;
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vdso_info.gnu_hash = 0;
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vdso_info.symtab = 0;
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vdso_info.versym = 0;
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vdso_info.verdef = 0;
···
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((uintptr_t)dyn[i].d_un.d_ptr
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+ vdso_info.load_offset);
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break;
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case DT_GNU_HASH:
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vdso_info.gnu_hash =
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(ELF(Word) *)((uintptr_t)dyn[i].d_un.d_ptr +
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vdso_info.load_offset);
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break;
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case DT_VERSYM:
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vdso_info.versym = (ELF(Versym) *)
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((uintptr_t)dyn[i].d_un.d_ptr
···
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break;
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}
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}
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-
if (!vdso_info.symstrings || !vdso_info.symtab || !hash)
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+
if (!vdso_info.symstrings || !vdso_info.symtab ||
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(!hash && !vdso_info.gnu_hash))
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return; /* Failed */
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if (!vdso_info.verdef)
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vdso_info.versym = 0;
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/* Parse the hash table header. */
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-
vdso_info.nbucket = hash[0];
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vdso_info.nchain = hash[1];
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-
vdso_info.bucket = &hash[2];
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-
vdso_info.chain = &hash[vdso_info.nbucket + 2];
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if (vdso_info.gnu_hash) {
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vdso_info.nbucket = vdso_info.gnu_hash[0];
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/* The bucket array is located after the header (4 uint32) and the bloom
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* filter (size_t array of gnu_hash[2] elements).
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*/
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vdso_info.bucket = vdso_info.gnu_hash + 4 +
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sizeof(size_t) / 4 * vdso_info.gnu_hash[2];
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} else {
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vdso_info.nbucket = hash[0];
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vdso_info.nchain = hash[1];
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vdso_info.bucket = &hash[2];
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vdso_info.chain = &hash[vdso_info.nbucket + 2];
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}
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/* That's all we need. */
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vdso_info.valid = true;
···
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&& !strcmp(name, vdso_info.symstrings + aux->vda_name);
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}
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+
static bool check_sym(ELF(Sym) *sym, ELF(Word) i, const char *name,
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const char *version, unsigned long ver_hash)
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{
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/* Check for a defined global or weak function w/ right name. */
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if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
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return false;
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if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
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ELF64_ST_BIND(sym->st_info) != STB_WEAK)
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return false;
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if (strcmp(name, vdso_info.symstrings + sym->st_name))
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return false;
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+
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/* Check symbol version. */
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if (vdso_info.versym &&
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!vdso_match_version(vdso_info.versym[i], version, ver_hash))
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return false;
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+
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return true;
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}
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+
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void *vdso_sym(const char *version, const char *name)
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{
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unsigned long ver_hash;
···
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return 0;
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ver_hash = elf_hash(version);
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-
ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
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ELF(Word) i;
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220
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-
for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
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-
ELF(Sym) *sym = &vdso_info.symtab[chain];
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if (vdso_info.gnu_hash) {
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uint32_t h1 = gnu_hash(name), h2, *hashval;
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223
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-
/* Check for a defined global or weak function w/ right name. */
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-
if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
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continue;
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-
if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
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-
ELF64_ST_BIND(sym->st_info) != STB_WEAK)
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continue;
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-
if (sym->st_shndx == SHN_UNDEF)
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-
continue;
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if (strcmp(name, vdso_info.symstrings + sym->st_name))
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continue;
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-
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/* Check symbol version. */
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if (vdso_info.versym
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-
&& !vdso_match_version(vdso_info.versym[chain],
285
-
version, ver_hash))
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continue;
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-
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-
return (void *)(vdso_info.load_offset + sym->st_value);
224
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i = vdso_info.bucket[h1 % vdso_info.nbucket];
225
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if (i == 0)
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return 0;
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h1 |= 1;
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hashval = vdso_info.bucket + vdso_info.nbucket +
229
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(i - vdso_info.gnu_hash[1]);
230
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for (;; i++) {
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ELF(Sym) *sym = &vdso_info.symtab[i];
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h2 = *hashval++;
233
+
if (h1 == (h2 | 1) &&
234
+
check_sym(sym, i, name, version, ver_hash))
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+
return (void *)(vdso_info.load_offset +
236
+
sym->st_value);
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if (h2 & 1)
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break;
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+
}
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} else {
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i = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
242
+
for (; i; i = vdso_info.chain[i]) {
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+
ELF(Sym) *sym = &vdso_info.symtab[i];
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+
if (sym->st_shndx != SHN_UNDEF &&
245
+
check_sym(sym, i, name, version, ver_hash))
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+
return (void *)(vdso_info.load_offset +
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+
sym->st_value);
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+
}
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}
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return 0;