Dear all,
The code bellow in the dladdr function has different behaviors at different optimization levels.
2219 if (bestsym && besterr > bestsym->st_size-1) {
2220 best = 0;
2221 bestsym = 0;
2222 }
Case of O1(arm32 little-endian):
154: e3580000 cmp r8, #0
158: 0a000003 beq 16c <dladdr+0x16c>
15c: e5983008 ldr r3, [r8, #8]
160: e2433001 sub r3, r3, #1
164: e153000a cmp r3, sl
168: 3a000011 bcc 1bc <dladdr+0x1b4>
Case of O2:
75e00: e5942044 ldr r2, [r4, #68] ; 0x44
75e04: e2433001 sub r3, r3, #1
75e08: e5941004 ldr r1, [r4, #4]
75e0c: e1530009 cmp r3, r9
75e10: 2a000007 bcs 75e34 <dladdr+0xfc>
75e14: e8870006 stm r7, {r1, r2}
In case of O2, the first part "bestsym" has been optimized, which may cause segment fault.
[patch]
Signed-off-by: l00383200 <liucheng32@huawei.com>
---
ldso/dynlink.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 7cb66db..c5f5fb7 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -2175,7 +2175,8 @@ int dladdr(const void *addr_arg, Dl_info *info)
{
size_t addr = (size_t)addr_arg;
struct dso *p;
- Sym *sym, *bestsym;
+ Sym *sym = NULL;
+ Sym *bestsym = NULL;
uint32_t nsym;
char *strings;
size_t best = 0;
--
1.8.5.6
[testcase]
------------
#define _GNU_SOURCE
#include <link.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <dlfcn.h>
static int callback(struct dl_phdr_info *info, size_t size, void *data)
{
int j,ret;
printf ("name=%s (%d segments)\n", info->dlpi_name, info->dlpi_phnum);
if(!strcmp(info->dlpi_name,"/lib/ld-musl-arm.so.1")) {
printf("ld-musl-arm have no indo\n");
return 0;
}
for (j = 0; j < info->dlpi_phnum; j++) {
void* addr = (void *) (info->dlpi_addr + info->dlpi_phdr[j].p_vaddr);
printf ("\t\t header %2d: address=%10p\n", j, addr);
Dl_info dlinfo;
ret = dladdr(addr, &dlinfo);
printf("\t\t\t %s : %s.", dlinfo.dli_fname, dlinfo.dli_sname);
if((addr == NULL && ret == 0) || (addr != NULL && ret == 1)) {
printf(" dladdr pass return:%d\n",ret);
} else {
printf(" dladdr error return:%d\n",ret);
}
}
return 0;
}
int main (int argc, char *argv[])
{
dl_iterate_phdr(callback, NULL);
exit(EXIT_SUCCESS);
}
------------