x86/vdso/doc: Make vDSO examples more portable
This adds a new vdso_test.c that's written entirely in C. It also
makes all of the vDSO examples work on 32-bit x86.
Cc: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/62b701fc44b79f118ac2b2d64d19965fc5c291fb.1402620737.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/Documentation/vDSO/parse_vdso.c b/Documentation/vDSO/parse_vdso.c
index 8587020..1dbb4b8 100644
--- a/Documentation/vDSO/parse_vdso.c
+++ b/Documentation/vDSO/parse_vdso.c
@@ -1,6 +1,6 @@
/*
* parse_vdso.c: Linux reference vDSO parser
- * Written by Andrew Lutomirski, 2011.
+ * Written by Andrew Lutomirski, 2011-2014.
*
* This code is meant to be linked in to various programs that run on Linux.
* As such, it is available with as few restrictions as possible. This file
@@ -11,13 +11,14 @@
* it starts a program. It works equally well in statically and dynamically
* linked binaries.
*
- * This code is tested on x86_64. In principle it should work on any 64-bit
+ * This code is tested on x86. In principle it should work on any
* architecture that has a vDSO.
*/
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
+#include <limits.h>
#include <elf.h>
/*
@@ -45,11 +46,18 @@
/* And here's the code. */
-
-#ifndef __x86_64__
-# error Not yet ported to non-x86_64 architectures
+#ifndef ELF_BITS
+# if ULONG_MAX > 0xffffffffUL
+# define ELF_BITS 64
+# else
+# define ELF_BITS 32
+# endif
#endif
+#define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
+#define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
+#define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
+
static struct vdso_info
{
bool valid;
@@ -59,14 +67,14 @@
uintptr_t load_offset; /* load_addr - recorded vaddr */
/* Symbol table */
- Elf64_Sym *symtab;
+ ELF(Sym) *symtab;
const char *symstrings;
- Elf64_Word *bucket, *chain;
- Elf64_Word nbucket, nchain;
+ ELF(Word) *bucket, *chain;
+ ELF(Word) nbucket, nchain;
/* Version table */
- Elf64_Versym *versym;
- Elf64_Verdef *verdef;
+ ELF(Versym) *versym;
+ ELF(Verdef) *verdef;
} vdso_info;
/* Straight from the ELF specification. */
@@ -92,9 +100,14 @@
vdso_info.load_addr = base;
- Elf64_Ehdr *hdr = (Elf64_Ehdr*)base;
- Elf64_Phdr *pt = (Elf64_Phdr*)(vdso_info.load_addr + hdr->e_phoff);
- Elf64_Dyn *dyn = 0;
+ ELF(Ehdr) *hdr = (ELF(Ehdr)*)base;
+ if (hdr->e_ident[EI_CLASS] !=
+ (ELF_BITS == 32 ? ELFCLASS32 : ELFCLASS64)) {
+ return; /* Wrong ELF class -- check ELF_BITS */
+ }
+
+ ELF(Phdr) *pt = (ELF(Phdr)*)(vdso_info.load_addr + hdr->e_phoff);
+ ELF(Dyn) *dyn = 0;
/*
* We need two things from the segment table: the load offset
@@ -108,7 +121,7 @@
+ (uintptr_t)pt[i].p_offset
- (uintptr_t)pt[i].p_vaddr;
} else if (pt[i].p_type == PT_DYNAMIC) {
- dyn = (Elf64_Dyn*)(base + pt[i].p_offset);
+ dyn = (ELF(Dyn)*)(base + pt[i].p_offset);
}
}
@@ -118,7 +131,7 @@
/*
* Fish out the useful bits of the dynamic table.
*/
- Elf64_Word *hash = 0;
+ ELF(Word) *hash = 0;
vdso_info.symstrings = 0;
vdso_info.symtab = 0;
vdso_info.versym = 0;
@@ -131,22 +144,22 @@
+ vdso_info.load_offset);
break;
case DT_SYMTAB:
- vdso_info.symtab = (Elf64_Sym *)
+ vdso_info.symtab = (ELF(Sym) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_HASH:
- hash = (Elf64_Word *)
+ hash = (ELF(Word) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_VERSYM:
- vdso_info.versym = (Elf64_Versym *)
+ vdso_info.versym = (ELF(Versym) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
case DT_VERDEF:
- vdso_info.verdef = (Elf64_Verdef *)
+ vdso_info.verdef = (ELF(Verdef) *)
((uintptr_t)dyn[i].d_un.d_ptr
+ vdso_info.load_offset);
break;
@@ -168,8 +181,8 @@
vdso_info.valid = true;
}
-static bool vdso_match_version(Elf64_Versym ver,
- const char *name, Elf64_Word hash)
+static bool vdso_match_version(ELF(Versym) ver,
+ const char *name, ELF(Word) hash)
{
/*
* This is a helper function to check if the version indexed by
@@ -188,7 +201,7 @@
/* First step: find the version definition */
ver &= 0x7fff; /* Apparently bit 15 means "hidden" */
- Elf64_Verdef *def = vdso_info.verdef;
+ ELF(Verdef) *def = vdso_info.verdef;
while(true) {
if ((def->vd_flags & VER_FLG_BASE) == 0
&& (def->vd_ndx & 0x7fff) == ver)
@@ -197,11 +210,11 @@
if (def->vd_next == 0)
return false; /* No definition. */
- def = (Elf64_Verdef *)((char *)def + def->vd_next);
+ def = (ELF(Verdef) *)((char *)def + def->vd_next);
}
/* Now figure out whether it matches. */
- Elf64_Verdaux *aux = (Elf64_Verdaux*)((char *)def + def->vd_aux);
+ ELF(Verdaux) *aux = (ELF(Verdaux)*)((char *)def + def->vd_aux);
return def->vd_hash == hash
&& !strcmp(name, vdso_info.symstrings + aux->vda_name);
}
@@ -213,10 +226,10 @@
return 0;
ver_hash = elf_hash(version);
- Elf64_Word chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
+ ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
- Elf64_Sym *sym = &vdso_info.symtab[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)
@@ -243,7 +256,7 @@
void vdso_init_from_auxv(void *auxv)
{
- Elf64_auxv_t *elf_auxv = auxv;
+ ELF(auxv_t) *elf_auxv = auxv;
for (int i = 0; elf_auxv[i].a_type != AT_NULL; i++)
{
if (elf_auxv[i].a_type == AT_SYSINFO_EHDR) {