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Message-ID: <20241206130724.7944-2-xry111@xry111.site>
Date: Fri, 6 Dec 2024 21:07:25 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Shuah Khan <shuah@...nel.org>,
Fangrui Song <i@...kray.me>,
linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Xi Ruoyao <xry111@...111.site>
Subject: [PATCH v3] selftests/vDSO: support DT_GNU_HASH
From: Fangrui Song <i@...kray.me>
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.
Signed-off-by: Fangrui Song <i@...kray.me>
Tested-by: Xi Ruoyao <xry111@...111.site>
Signed-off-by: Xi Ruoyao <xry111@...111.site> # rebase
---
tools/testing/selftests/vDSO/parse_vdso.c | 110 ++++++++++++++++------
1 file changed, 82 insertions(+), 28 deletions(-)
diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
index 28f35620c499..2fe5e983cb22 100644
--- a/tools/testing/selftests/vDSO/parse_vdso.c
+++ b/tools/testing/selftests/vDSO/parse_vdso.c
@@ -53,6 +53,7 @@ static struct vdso_info
/* Symbol table */
ELF(Sym) *symtab;
const char *symstrings;
+ ELF(Word) *gnu_hash;
ELF_HASH_ENTRY *bucket, *chain;
ELF_HASH_ENTRY nbucket, nchain;
@@ -81,6 +82,16 @@ static unsigned long elf_hash(const char *name)
return h;
}
+static uint32_t gnu_hash(const char *name)
+{
+ const unsigned char *s = (void *)name;
+ uint32_t h = 5381;
+
+ for (; *s; s++)
+ h += h * 32 + *s;
+ return h;
+}
+
void vdso_init_from_sysinfo_ehdr(uintptr_t base)
{
size_t i;
@@ -123,6 +134,7 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
*/
ELF_HASH_ENTRY *hash = 0;
vdso_info.symstrings = 0;
+ vdso_info.gnu_hash = 0;
vdso_info.symtab = 0;
vdso_info.versym = 0;
vdso_info.verdef = 0;
@@ -143,6 +155,11 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
+ case DT_GNU_HASH:
+ vdso_info.gnu_hash =
+ (ELF(Word) *)((uintptr_t)dyn[i].d_un.d_ptr +
+ vdso_info.load_offset);
+ break;
case DT_VERSYM:
vdso_info.versym = (ELF(Versym) *)
((uintptr_t)dyn[i].d_un.d_ptr
@@ -155,17 +172,27 @@ void vdso_init_from_sysinfo_ehdr(uintptr_t base)
break;
}
}
- if (!vdso_info.symstrings || !vdso_info.symtab || !hash)
+ if (!vdso_info.symstrings || !vdso_info.symtab ||
+ (!hash && !vdso_info.gnu_hash))
return; /* Failed */
if (!vdso_info.verdef)
vdso_info.versym = 0;
/* Parse the hash table header. */
- vdso_info.nbucket = hash[0];
- vdso_info.nchain = hash[1];
- vdso_info.bucket = &hash[2];
- vdso_info.chain = &hash[vdso_info.nbucket + 2];
+ if (vdso_info.gnu_hash) {
+ vdso_info.nbucket = vdso_info.gnu_hash[0];
+ /* The bucket array is located after the header (4 uint32) and the bloom
+ * filter (size_t array of gnu_hash[2] elements).
+ */
+ vdso_info.bucket = vdso_info.gnu_hash + 4 +
+ sizeof(size_t) / 4 * vdso_info.gnu_hash[2];
+ } else {
+ vdso_info.nbucket = hash[0];
+ vdso_info.nchain = hash[1];
+ vdso_info.bucket = &hash[2];
+ vdso_info.chain = &hash[vdso_info.nbucket + 2];
+ }
/* That's all we need. */
vdso_info.valid = true;
@@ -209,6 +236,26 @@ static bool vdso_match_version(ELF(Versym) ver,
&& !strcmp(name, vdso_info.symstrings + aux->vda_name);
}
+static bool check_sym(ELF(Sym) *sym, ELF(Word) i, const char *name,
+ const char *version, unsigned long ver_hash)
+{
+ /* Check for a defined global or weak function w/ right name. */
+ if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
+ return false;
+ if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
+ ELF64_ST_BIND(sym->st_info) != STB_WEAK)
+ return false;
+ if (strcmp(name, vdso_info.symstrings + sym->st_name))
+ return false;
+
+ /* Check symbol version. */
+ if (vdso_info.versym &&
+ !vdso_match_version(vdso_info.versym[i], version, ver_hash))
+ return false;
+
+ return true;
+}
+
void *vdso_sym(const char *version, const char *name)
{
unsigned long ver_hash;
@@ -216,29 +263,36 @@ void *vdso_sym(const char *version, const char *name)
return 0;
ver_hash = elf_hash(version);
- ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
-
- for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
- ELF(Sym) *sym = &vdso_info.symtab[chain];
-
- /* Check for a defined global or weak function w/ right name. */
- if (ELF64_ST_TYPE(sym->st_info) != STT_FUNC)
- continue;
- if (ELF64_ST_BIND(sym->st_info) != STB_GLOBAL &&
- ELF64_ST_BIND(sym->st_info) != STB_WEAK)
- continue;
- if (sym->st_shndx == SHN_UNDEF)
- continue;
- if (strcmp(name, vdso_info.symstrings + sym->st_name))
- continue;
-
- /* Check symbol version. */
- if (vdso_info.versym
- && !vdso_match_version(vdso_info.versym[chain],
- version, ver_hash))
- continue;
-
- return (void *)(vdso_info.load_offset + sym->st_value);
+ ELF(Word) i;
+
+ if (vdso_info.gnu_hash) {
+ uint32_t h1 = gnu_hash(name), h2, *hashval;
+
+ i = vdso_info.bucket[h1 % vdso_info.nbucket];
+ if (i == 0)
+ return 0;
+ h1 |= 1;
+ hashval = vdso_info.bucket + vdso_info.nbucket +
+ (i - vdso_info.gnu_hash[1]);
+ for (;; i++) {
+ ELF(Sym) *sym = &vdso_info.symtab[i];
+ h2 = *hashval++;
+ if (h1 == (h2 | 1) &&
+ check_sym(sym, i, name, version, ver_hash))
+ return (void *)(vdso_info.load_offset +
+ sym->st_value);
+ if (h2 & 1)
+ break;
+ }
+ } else {
+ i = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
+ for (; i; i = vdso_info.chain[i]) {
+ ELF(Sym) *sym = &vdso_info.symtab[i];
+ if (sym->st_shndx != SHN_UNDEF &&
+ check_sym(sym, i, name, version, ver_hash))
+ return (void *)(vdso_info.load_offset +
+ sym->st_value);
+ }
}
return 0;
base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
--
2.47.1
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