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BUG/MEDIUM: tools: avoid calling dlsym() in static builds (try 2)

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The first approach in commit 288dc1d8e ("BUG/MEDIUM: tools: avoid calling
dlsym() in static builds") relied on dlopen() but on certain configs (at
least gcc-4.8+ld-2.27+glibc-2.17) it used to catch situations where it
ought not fail.

Let's have a second try on this using dladdr() instead. The variable was
renamed "build_is_static" as it's exactly what's being detected there.
We could even take it for reporting in -vv though that doesn't seem very
useful. At least the variable was made global to ease inspection via the
debugger, or in case it's useful later.

Now it properly detects a static build even with gcc-4.4+glibc-2.11.1 and
doesn't crash anymore.
This commit is contained in:
Willy Tarreau 2022-07-18 13:58:17 +02:00
parent bc50e0d0fb
commit 5b3cd9561b
2 changed files with 21 additions and 14 deletions
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1
include/haproxy/tools.h
View File

@ -70,6 +70,7 @@ extern int strlcpy2(char *dst, const char *src, int size);
*/ */
extern THREAD_LOCAL int itoa_idx; /* index of next itoa_str to use */ extern THREAD_LOCAL int itoa_idx; /* index of next itoa_str to use */
extern THREAD_LOCAL char itoa_str[][171]; extern THREAD_LOCAL char itoa_str[][171];
extern int build_is_static;
extern char *ultoa_r(unsigned long n, char *buffer, int size); extern char *ultoa_r(unsigned long n, char *buffer, int size);
extern char *lltoa_r(long long int n, char *buffer, int size); extern char *lltoa_r(long long int n, char *buffer, int size);
extern char *sltoa_r(long n, char *buffer, int size); extern char *sltoa_r(long n, char *buffer, int size);

34
src/tools.c
View File

@ -98,6 +98,9 @@ THREAD_LOCAL int quoted_idx = 0;
*/ */
THREAD_LOCAL unsigned int statistical_prng_state = 2463534242U; THREAD_LOCAL unsigned int statistical_prng_state = 2463534242U;
/* set to true if this is a static build */
int build_is_static = 0;
/* /*
* unsigned long long ASCII representation * unsigned long long ASCII representation
* *
@ -4920,22 +4923,25 @@ static int dladdr_and_size(const void *addr, Dl_info *dli, size_t *size)
return ret; return ret;
} }
/* dlopen() support: 0=no/not yet checked, 1=ok */ /* Sets build_is_static to true if we detect a static build. Some older glibcs
static int dlopen_usable = 0; * tend to crash inside dlsym() in static builds, but tests show that at least
* dladdr() still works (and will fail to resolve anything of course). Thus we
/* Sets dlopen_usable to true if dlopen() works and is usable. We verify if * try to determine if we're on a static build to avoid calling dlsym() in this
* we're in a static build because some old glibcs used to crash in dlsym() * case.
* in this case.
*/ */
void check_if_dlopen_usable() void check_if_static_build()
{ {
/* dlopen(NULL) returns a handle to the main program or NULL Dl_info dli = { };
* on static builds. size_t size = 0;
*/
dlopen_usable = dlopen(NULL, RTLD_LAZY) ? 1 : 0; /* Now let's try to be smarter */
if (!dladdr_and_size(&main, &dli, &size))
build_is_static = 1;
else
build_is_static = 0;
} }
INITCALL0(STG_PREPARE, check_if_dlopen_usable); INITCALL0(STG_PREPARE, check_if_static_build);
/* Tries to retrieve the address of the first occurrence symbol <name>. /* Tries to retrieve the address of the first occurrence symbol <name>.
* Note that NULL in return is not always an error as a symbol may have that * Note that NULL in return is not always an error as a symbol may have that
@ -4946,7 +4952,7 @@ void *get_sym_curr_addr(const char *name)
void *ptr = NULL; void *ptr = NULL;
#ifdef RTLD_DEFAULT #ifdef RTLD_DEFAULT
if (dlopen_usable) if (!build_is_static)
ptr = dlsym(RTLD_DEFAULT, name); ptr = dlsym(RTLD_DEFAULT, name);
#endif #endif
return ptr; return ptr;
@ -4962,7 +4968,7 @@ void *get_sym_next_addr(const char *name)
void *ptr = NULL; void *ptr = NULL;
#ifdef RTLD_NEXT #ifdef RTLD_NEXT
if (dlopen_usable) if (!build_is_static)
ptr = dlsym(RTLD_NEXT, name); ptr = dlsym(RTLD_NEXT, name);
#endif #endif
return ptr; return ptr;