Kernel dso support for 'dl_iterate_phdr' function
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
diff --git a/libc/bionic/dl_iterate_phdr_static.c b/libc/bionic/dl_iterate_phdr_static.c
index 90ed1b7..fc79ce5 100644
--- a/libc/bionic/dl_iterate_phdr_static.c
+++ b/libc/bionic/dl_iterate_phdr_static.c
@@ -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
}