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Kernel dso support for 'dl_iterate_phdr' function

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Kernel provides virtual DSO for stack unwinding/exception handlind info for
signal usage case. Stack unwinding routines use 'dl_iterate_phdr' function
for additional DWARF info gathering from DSOs. Patch enables virtual DSO
enumeration via dl_iterate_phdr function.

Signed-off-by: Sergey Melnikov <sergey.melnikov@intel.com>
Change-Id: Ic2882b28f40b456a088bc1e63c50cbfda7e4a102
This commit is contained in:
Sergey Melnikov
2013-01-25 16:40:13 +04:00
committed by Elliott Hughes
parent bfacb603e4
commit c45087bffa
5 changed files with 186 additions and 25 deletions
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65
libc/bionic/dl_iterate_phdr_static.c
View File

@@ -27,39 +27,56 @@
*/
#include <elf.h>
#include <sys/auxv.h>
#include <sys/types.h>
#include <link.h>
/* Dynamic binaries get this from the dynamic linker (system/linker), which
* we don't pull in for static bins. We also don't have a list of so's to
* iterate over, since there's really only a single monolithic blob of
* code/data.
*
* All we need to do is to find where the executable is in memory, and grab the
* phdr and phnum from there.
*/
/* ld provides this to us in the default link script */
extern void *__executable_start;
extern void* __executable_start;
int
dl_iterate_phdr(int (*cb)(struct dl_phdr_info *info, size_t size, void *data),
void *data)
{
struct dl_phdr_info dl_info;
Elf32_Ehdr *ehdr = (Elf32_Ehdr *) &__executable_start;
Elf32_Phdr *phdr = (Elf32_Phdr *)((unsigned long)ehdr + ehdr->e_phoff);
int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data), void* data) {
Elf32_Ehdr* ehdr = (Elf32_Ehdr*) &__executable_start;
/* TODO: again, copied from linker.c. Find a better home for this
* later. */
// TODO: again, copied from linker.c. Find a better home for this later.
if (ehdr->e_ident[EI_MAG0] != ELFMAG0) return -1;
if (ehdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
if (ehdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
if (ehdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
dl_info.dlpi_addr = 0;
dl_info.dlpi_name = NULL;
dl_info.dlpi_phdr = phdr;
dl_info.dlpi_phnum = ehdr->e_phnum;
return cb(&dl_info, sizeof (struct dl_phdr_info), data);
// Dynamic binaries get their dl_iterate_phdr from the dynamic linker, but
// static binaries get this. We don't have a list of shared objects to
// iterate over, since there's really only a single monolithic blob of
// code/data, plus optionally a VDSO.
struct dl_phdr_info exe_info;
exe_info.dlpi_addr = 0;
exe_info.dlpi_name = NULL;
exe_info.dlpi_phdr = (Elf32_Phdr*) ((unsigned long) ehdr + ehdr->e_phoff);
exe_info.dlpi_phnum = ehdr->e_phnum;
#ifdef AT_SYSINFO_EHDR
// Try the executable first.
int rc = cb(&exe_info, sizeof(exe_info), data);
if (rc != 0) {
return rc;
}
// Try the VDSO if that didn't work.
Elf32_Ehdr* ehdr_vdso = (Elf32_Ehdr*) getauxval(AT_SYSINFO_EHDR);
struct dl_phdr_info vdso_info;
vdso_info.dlpi_addr = 0;
vdso_info.dlpi_name = NULL;
vdso_info.dlpi_phdr = (Elf32_Phdr*) ((char*) ehdr_vdso + ehdr_vdso->e_phoff);
vdso_info.dlpi_phnum = ehdr_vdso->e_phnum;
for (size_t i = 0; i < vdso_info.dlpi_phnum; ++i) {
if (vdso_info.dlpi_phdr[i].p_type == PT_LOAD) {
vdso_info.dlpi_addr = (Elf32_Addr) ehdr_vdso - vdso_info.dlpi_phdr[i].p_vaddr;
break;
}
}
return cb(&vdso_info, sizeof(vdso_info), data);
#else
// There's only the executable to try.
return cb(&exe_info, sizeof(exe_info), data);
#endif
}