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make dlerror produce informative results

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note that dlerror is specified to be non-thread-safe, so no locking is
performed on the error flag or message aside from the rwlock already
held by dlopen or dlsym. if 2 invocations of dlsym are generating
errors at the same time, they could clobber each other's results, but
the resulting string, albeit corrupt, will still be null-terminated.
any use of dlerror in such a situation could not be expected to give
meaningful results anyway.
This commit is contained in:
Rich Felker 2012-04-23 12:03:31 -04:00
parent 90da74ef51
commit a5d10eb1f5
1 changed files with 15 additions and 4 deletions
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19
src/ldso/dynlink.c
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@ -18,6 +18,7 @@
#include <dlfcn.h> #include <dlfcn.h>
static int errflag; static int errflag;
static char errbuf[128];
#ifdef __PIC__ #ifdef __PIC__
@ -142,8 +143,11 @@ static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t
ctx = IS_COPY(type) ? dso->next : dso; ctx = IS_COPY(type) ? dso->next : dso;
sym_val = (size_t)find_sym(ctx, name, IS_PLT(type)); sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
if (!sym_val && sym->st_info>>4 != STB_WEAK) { if (!sym_val && sym->st_info>>4 != STB_WEAK) {
snprintf(errbuf, sizeof errbuf,
"Error relocating %s: %s: symbol not found",
dso->name, name);
if (runtime) longjmp(rtld_fail, 1); if (runtime) longjmp(rtld_fail, 1);
dprintf(2, "%s: symbol not found\n", name); dprintf(2, "%s\n", errbuf);
_exit(127); _exit(127);
} }
sym_size = sym->st_size; sym_size = sym->st_size;
@ -405,9 +409,11 @@ static void load_deps(struct dso *p)
if (p->dynv[i] != DT_NEEDED) continue; if (p->dynv[i] != DT_NEEDED) continue;
dep = load_library(p->strings + p->dynv[i+1]); dep = load_library(p->strings + p->dynv[i+1]);
if (!dep) { if (!dep) {
if (runtime) longjmp(rtld_fail, 1); snprintf(errbuf, sizeof errbuf,
dprintf(2, "%s: %m (needed by %s)\n", "Error loading shared library %s: %m (needed by %s)",
p->strings + p->dynv[i+1], p->name); p->strings + p->dynv[i+1], p->name);
if (runtime) longjmp(rtld_fail, 1);
dprintf(2, "%s\n", errbuf);
_exit(127); _exit(127);
} }
if (runtime) { if (runtime) {
@ -634,9 +640,13 @@ void *dlopen(const char *file, int mode)
tail = orig_tail; tail = orig_tail;
tail->next = 0; tail->next = 0;
p = 0; p = 0;
errflag = 1;
goto end;
} else p = load_library(file); } else p = load_library(file);
if (!p) { if (!p) {
snprintf(errbuf, sizeof errbuf,
"Error loading shared library %s: %m", file);
errflag = 1; errflag = 1;
goto end; goto end;
} }
@ -694,6 +704,7 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)
return p->deps[i]->base + sym->st_value; return p->deps[i]->base + sym->st_value;
} }
errflag = 1; errflag = 1;
snprintf(errbuf, sizeof errbuf, "Symbol not found: %s", s);
return 0; return 0;
} }
@ -720,7 +731,7 @@ char *dlerror()
{ {
if (!errflag) return 0; if (!errflag) return 0;
errflag = 0; errflag = 0;
return "unknown error"; return errbuf;
} }
int dlclose(void *p) int dlclose(void *p)