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add time64 redirect for, and redirecting implementation of, dlsym

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if symbols are being redirected to provide the new time64 ABI, dlsym
must perform matching redirections; otherwise, it would poke a hole in
the magic and return pointers to functions that are not safe to call
from a caller using time64 types.

rather than duplicating a table of redirections, use the time64
symbols present in libc's symbol table to derive the decision for
whether a particular symbol needs to be redirected.
This commit is contained in:
Rich Felker 2019-08-09 15:26:23 -04:00
parent c045032094
commit 22daaea39f
2 changed files with 31 additions and 0 deletions
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4
include/dlfcn.h
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@ -35,6 +35,10 @@ int dladdr(const void *, Dl_info *);
int dlinfo(void *, int, void *); int dlinfo(void *, int, void *);
#endif #endif
#if _REDIR_TIME64
__REDIR(dlsym, __dlsym_time64);
#endif
#ifdef __cplusplus #ifdef __cplusplus
} }
#endif #endif

27
ldso/dynlink.c
View File

@ -2237,6 +2237,33 @@ hidden void *__dlsym(void *restrict p, const char *restrict s, void *restrict ra
return res; return res;
} }
hidden void *__dlsym_redir_time64(void *restrict p, const char *restrict s, void *restrict ra)
{
#if _REDIR_TIME64
const char *suffix, *suffix2 = "";
char redir[36];
/* Map the symbol name to a time64 version of itself according to the
* pattern used for naming the redirected time64 symbols. */
size_t l = strnlen(s, sizeof redir);
if (l<4 || l==sizeof redir) goto no_redir;
if (s[l-2]=='_' && s[l-1]=='r') {
l -= 2;
suffix2 = s+l;
}
if (l<4) goto no_redir;
if (!strcmp(s+l-4, "time")) suffix = "64";
else suffix = "_time64";
/* Use the presence of the remapped symbol name in libc to determine
* whether it's one that requires time64 redirection; replace if so. */
snprintf(redir, sizeof redir, "__%.*s%s%s", (int)l, s, suffix, suffix2);
if (find_sym(&ldso, redir, 1).sym) s = redir;
no_redir:
#endif
return __dlsym(p, s, ra);
}
int dl_iterate_phdr(int(*callback)(struct dl_phdr_info *info, size_t size, void *data), void *data) int dl_iterate_phdr(int(*callback)(struct dl_phdr_info *info, size_t size, void *data), void *data)
{ {
struct dso *current; struct dso *current;