[uclibc-ng-devel] Re: [PATCH 1/2] Make getauxval work with static linking

Hi Waldemar,

our apologies. I only compiled this in our environment where the failing code is not used. We can reproduce the issue and are looking for a fix.

- Marcus

On Thu, 2025-03-06 at 14:08 +0100, Waldemar Brodkorb wrote:

Hi Marcus,

I accidentally pushed the changes and now get following build error:

libc/misc/internals/__uClibc_main.c: In function '__uClibc_main': libc/misc/internals/__uClibc_main.c:424:10: error: '_dl_auxvt' undeclared (first use in this function); did you mean '_dl_aux_init'? 424 | if ((_dl_auxvt[AT_UID].a_un.a_val == (size_t)-1 && __check_suid()) || | ^~~~~~~~~ | _dl_aux_init libc/misc/internals/__uClibc_main.c:424:10: note: each undeclared identifier is reported only once for each function it appears in gmake[6]: *** [Makerules:373: libc/misc/internals/__uClibc_main.os] Error 1 gmake[5]: *** [Makefile:353: /home/wbx/embedded-test/openadk/toolchain_build_qemu-aarch64_uclibc-ng_cortex_a53/w-uClibc-ng-1.0.51-1/uClibc-ng-1.0.51/.compiled] Error 2 gmake[4]: *** [Makefile:106: uclibc-ng-compile] Error 2 gmake[3]: *** [mk/build.mk:229: toolchain/final] Error 2 gmake[2]: *** [/home/wbx/embedded-test/openadk/mk/build.mk:174: world] Error 2 gmake[1]: *** [Makefile.adk:25: all] Error 2 make: *** [Makefile:22: all] Error 2 build failed wbx@helium:~/embedded-test$

Any idea why it fails for me and not for you? Targeting aarch64 with uClibc-ng master.

best regards Waldemar

Marcus Haehnel wrote,

...

From: Georg Kotheimer georg.kotheimer@kernkonzept.com

While for dynamic linking the _dl_auxvt array is provided in dl-startup.c as part of the ldso, is was undefined for statically linked binaries. This resulted in a corresponding linker error if a statically linked program used getauxval.

To provide _dl_auxvt also for statically linked binaries, a definition of _dl_auxvt is added to dl-support.c and initialized by _dl_aux_init().

Signed-off-by: Marcus Haehnel marcus.haehnel@kernkonzept.com

libc/misc/elf/dl-support.c | 16 +++++++++++++--- libc/misc/internals/__uClibc_main.c | 22 ++++++---------------- 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/libc/misc/elf/dl-support.c b/libc/misc/elf/dl-support.c index 87cd1bb72..81c78fa55 100644 --- a/libc/misc/elf/dl-support.c +++ b/libc/misc/elf/dl-support.c @@ -12,6 +12,7 @@ */

#include <link.h> +#include <ldso.h> #include <elf.h> #if defined(USE_TLS) && USE_TLS #include <assert.h> @@ -31,17 +32,26 @@ ElfW(Phdr) *_dl_phdr; size_t _dl_phnum; size_t _dl_pagesize;

+ElfW(auxv_t) _dl_auxvt[AUX_MAX_AT_ID];

void internal_function _dl_aux_init (ElfW(auxv_t) *av); void internal_function _dl_aux_init (ElfW(auxv_t) *av) {

• memset(_dl_auxvt, 0x00, sizeof(_dl_auxvt));
• for (; av->a_type != AT_NULL; av++)

• {
  

•   if (av->a_type < AUX_MAX_AT_ID)
  

•     _dl_auxvt[av->a_type] = *av;
  

• }
  

• /* Get the program headers base address from the aux vect */

• _dl_phdr = (ElfW(Phdr) *) av[AT_PHDR].a_un.a_val;

• _dl_phdr = (ElfW(Phdr) *) _dl_auxvt[AT_PHDR].a_un.a_val;

  /* Get the number of program headers from the aux vect */

• _dl_phnum = (size_t) av[AT_PHNUM].a_un.a_val;

• _dl_phnum = (size_t) _dl_auxvt[AT_PHNUM].a_un.a_val;

  /* Get the pagesize from the aux vect */

• _dl_pagesize = (av[AT_PAGESZ].a_un.a_val) ? (size_t) av[AT_PAGESZ].a_un.a_val : PAGE_SIZE;

• _dl_pagesize = (_dl_auxvt[AT_PAGESZ].a_un.a_val) ? (size_t) _dl_auxvt[AT_PAGESZ].a_un.a_val : PAGE_SIZE;

}

#if defined(USE_TLS) && USE_TLS diff --git a/libc/misc/internals/__uClibc_main.c b/libc/misc/internals/__uClibc_main.c index 64a9c8214..a84492248 100644 --- a/libc/misc/internals/__uClibc_main.c +++ b/libc/misc/internals/__uClibc_main.c @@ -43,7 +43,7 @@ /* Are we in a secure process environment or are we dealing

• with setuid stuff? If we are dynamically linked, then we
• already have _dl_secure, otherwise we need to re-examine

• • auxvt[] below.

• • _dl_auxvt[] below.
  */

int _pe_secure = 0; libc_hidden_data_def(_pe_secure) @@ -373,7 +373,6 @@ void __uClibc_main(int (*main)(int, char **, char **), int argc, { #ifndef SHARED unsigned long *aux_dat;

• ElfW(auxv_t) auxvt[AT_EGID + 1];

#endif

#ifdef __UCLIBC_HAS_THREADS_NATIVE__ @@ -399,23 +398,14 @@ void __uClibc_main(int (*main)(int, char **, char **), int argc,

#ifndef SHARED /* Pull stuff from the ELF header when possible */

• memset(auxvt, 0x00, sizeof(auxvt)); aux_dat = (unsigned long*)__environ; while (*aux_dat) { aux_dat++; } aux_dat++;
• while (*aux_dat) {
• ElfW(auxv_t) *auxv_entry = (ElfW(auxv_t) *) aux_dat;
• if (auxv_entry->a_type <= AT_EGID) {

•    memcpy(&(auxvt[auxv_entry->a_type]), auxv_entry, sizeof(ElfW(auxv_t)));
  

• }
• aux_dat += 2;
• } /* Get the program headers (_dl_phdr) from the aux vector It will be used into __libc_setup_tls. */
• _dl_aux_init (auxvt);

• _dl_aux_init ((ElfW(auxv_t) *)aux_dat);

#endif

 /* We need to initialize uClibc.  If we are dynamically linked this

@@ -431,10 +421,10 @@ void __uClibc_main(int (*main)(int, char **, char **), int argc, #ifndef SHARED /* Prevent starting SUID binaries where the stdin. stdout, and * stderr file descriptors are not already opened. */

• if ((auxvt[AT_UID].a_un.a_val == (size_t)-1 && __check_suid()) ||

•    (auxvt[AT_UID].a_un.a_val != (size_t)-1 &&
  

•    (auxvt[AT_UID].a_un.a_val != auxvt[AT_EUID].a_un.a_val ||
  

•     auxvt[AT_GID].a_un.a_val != auxvt[AT_EGID].a_un.a_val)))
  

• if ((_dl_auxvt[AT_UID].a_un.a_val == (size_t)-1 && __check_suid()) ||

•    (_dl_auxvt[AT_UID].a_un.a_val != (size_t)-1 &&
  

•    (_dl_auxvt[AT_UID].a_un.a_val != _dl_auxvt[AT_EUID].a_un.a_val ||
  

•     _dl_auxvt[AT_GID].a_un.a_val != _dl_auxvt[AT_EGID].a_un.a_val)))
  

#else if (_dl_secure)

#endif

2.47.1

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