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remove freeing of dynamic linker data when dlopen/dlsym are not used 

this was an optimization to save/recover a minimal amount of extra
memory for use by malloc, that's becoming increasingly costly to keep
around. freeing this data:

1. breaks debugging with gdb (it can't find library symbols)
2. breaks thread-local storage in shared libraries

it would be possible to disable freeing when TLS is used, but in
addition to the above breakages, tracking whether dlopen/dlsym is used
adds a cost to every symbol lookup, possibly making program startup
slower for large programs. combined with the complexity, it's not
worth it. we already save/recover plenty of memory in the dynamic
linker with reclaim_gaps.
This commit is contained in:
Rich Felker 2012-10-04 21:08:53 -04:00
parent 9b153c043e
commit c91aa03d24
1 changed files with 0 additions and 11 deletions
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11
src/ldso/dynlink.c
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@ -80,7 +80,6 @@ void *__install_initial_tls(void *);
static struct dso *head, *tail, *libc; static struct dso *head, *tail, *libc;
static char *env_path, *sys_path, *r_path; static char *env_path, *sys_path, *r_path;
static int rtld_used;
static int ssp_used; static int ssp_used;
static int runtime; static int runtime;
static int ldd_mode; static int ldd_mode;
@ -182,13 +181,9 @@ static void *find_sym(struct dso *dso, const char *s, int need_def)
void *def = 0; void *def = 0;
if (dso->ghashtab) { if (dso->ghashtab) {
gh = gnu_hash(s); gh = gnu_hash(s);
if (gh == 0xf9040207 && !strcmp(s, "dlopen")) rtld_used = 1;
if (gh == 0xf4dc4ae && !strcmp(s, "dlsym")) rtld_used = 1;
if (gh == 0x1f4039c9 && !strcmp(s, "__stack_chk_fail")) ssp_used = 1; if (gh == 0x1f4039c9 && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
} else { } else {
h = sysv_hash(s); h = sysv_hash(s);
if (h == 0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
if (h == 0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
if (h == 0x595a4cc && !strcmp(s, "__stack_chk_fail")) ssp_used = 1; if (h == 0x595a4cc && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
} }
for (; dso; dso=dso->next) { for (; dso; dso=dso->next) {
@ -862,12 +857,6 @@ void *__dynlink(int argc, char **argv)
do_init_fini(tail); do_init_fini(tail);
if (!rtld_used) {
free_all(head);
free(sys_path);
reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos);
}
errno = 0; errno = 0;
return (void *)aux[AT_ENTRY]; return (void *)aux[AT_ENTRY];
} }