glibc/elf/Makefile, branch master

elf: Make dl-rseq-symbols Linux only

2024-07-04T13:09:07Z

And avoid a Hurd build failures. Checked on x86_64-linux-gnu.

nptl: fix potential merge of __rseq_* relro symbols

2024-07-03T19:40:30Z

While working on a patch to add support for the extensible rseq ABI, we came across an issue where a new 'const' variable would be merged with the existing '__rseq_size' variable. We tracked this to the use of '-fmerge-all-constants' which allows the compiler to merge identical constant variables. This means that all 'const' variables in a compile unit that are of the same size and are initialized to the same value can be merged. In this specific case, on 32 bit systems 'unsigned int' and 'ptrdiff_t' are both 4 bytes and initialized to 0 which should trigger the merge. However for reasons we haven't delved into when the attribute 'section (".data.rel.ro")' is added to the mix, only variables of the same exact types are merged. As far as we know this behavior is not specified anywhere and could change with a new compiler version, hence this patch. Move the definitions of these variables into an assembler file and add hidden writable aliases for internal use. This has the added bonus of removing the asm workaround to set the values on rseq registration. Tested on Debian 12 with GCC 12.2. Signed-off-by: Michael Jeanson Reviewed-by: Mathieu Desnoyers Reviewed-by: Florian Weimer

elf/rtld: Fix auxiliary vector for enable_secure

2024-07-03T11:01:44Z

Starting with commit 59974938fe1f4add843f5325f78e2a7ccd8db853 elf/rtld: Count skipped environment variables for enable_secure The new testcase elf/tst-tunables-enable_secure-env segfaults on s390 (31bit). There _start parses the auxiliary vector for some additional checks. Therefore it skips over the zeros after the environment variables ... 0x7fffac20: 0x7fffbd17 0x7fffbd32 0x7fffbd69 0x00000000 ------------------------------------------------^^^last environment variable ... and then it parses the auxiliary vector and stops at AT_NULL. 0x7fffac30: 0x00000000 0x00000021 0x00000000 0x00000000 --------------------------------^^^AT_SYSINFO_EHDR--------------^^^AT_NULL ----------------^^^newp-----------------------------------------^^^oldp Afterwards it tries to access AT_PHDR which points to somewhere and segfaults. Due to not incorporating the skip_env variable in the computation of oldp when shuffling down the auxv in rtld.c, it just copies one entry with AT_NULL and value 0x00000021 and stops the loop. In reality we have skipped GLIBC_TUNABLES environment variable (=> skip_env=1). Thus we should copy from here: 0x7fffac40: 0x00000021 0x7ffff000 0x00000010 0x007fffff ----------------^^^fixed-oldp This patch fixes the computation of oldp when shuffling down auxiliary vector. It also adds some checks in the testcase. Those checks also fail on s390x (64bit) and x86_64 without the fix. Co-authored-by: Adhemerval Zanella Reviewed-by: Adhemerval Zanella

elf: Support recursive use of dynamic TLS in interposed malloc

2024-07-01T17:02:11Z

It turns out that quite a few applications use bundled mallocs that have been built to use global-dynamic TLS (instead of the recommended initial-exec TLS). The previous workaround from commit afe42e935b3ee97bac9a7064157587777259c60e ("elf: Avoid some free (NULL) calls in _dl_update_slotinfo") does not fix all encountered cases unfortunatelly. This change avoids the TLS generation update for recursive use of TLS from a malloc that was called during a TLS update. This is possible because an interposed malloc has a fixed module ID and TLS slot. (It cannot be unloaded.) If an initially-loaded module ID is encountered in __tls_get_addr and the dynamic linker is already in the middle of a TLS update, use the outdated DTV, thus avoiding another call into malloc. It's still necessary to update the DTV to the most recent generation, to get out of the slow path, which is why the check for recursion is needed. The bookkeeping is done using a global counter instead of per-thread flag because TLS access in the dynamic linker is tricky. All this will go away once the dynamic linker stops using malloc for TLS, likely as part of a change that pre-allocates all TLS during pthread_create/dlopen. Fixes commit d2123d68275acc0f061e73d5f86ca504e0d5a344 ("elf: Fix slow tls access after dlopen [BZ #19924]"). Reviewed-by: Szabolcs Nagy

Fix conditionals on mtrace-based tests (bug 31892)

2024-07-01T15:20:30Z

The conditionals for several mtrace-based tests in catgets, elf, libio, malloc, misc, nptl, posix, and stdio-common were incorrect leading to test failures when bootstrapping glibc without perl. The correct conditional for mtrace-based tests requires three checks: first checking for run-built-tests, then build-shared, and lastly that PERL is not equal to "no" (missing perl). Reviewed-by: Adhemerval Zanella

elf: Change module-names to modules-names in comments

2024-06-14T20:29:21Z

module-names should be modules-names. Signed-off-by: H.J. Lu

elf/Makefile: Split and sort PIE tests

2024-05-25T21:53:30Z

Put each item on a separate line and sort PIE tests. Signed-off-by: H.J. Lu

elf: Also compile dl-misc.os with $(rtld-early-cflags)

2024-04-25T15:09:49Z

Also compile dl-misc.os with $(rtld-early-cflags) to avoid Program received signal SIGILL, Illegal instruction. 0x00007ffff7fd36ea in _dl_strtoul (nptr=nptr@entry=0x7fffffffe2c9 "2", endptr=endptr@entry=0x7fffffffd728) at dl-misc.c:156 156 bool positive = true; (gdb) bt #0 0x00007ffff7fd36ea in _dl_strtoul (nptr=nptr@entry=0x7fffffffe2c9 "2", endptr=endptr@entry=0x7fffffffd728) at dl-misc.c:156 #1 0x00007ffff7fdb1a9 in tunable_initialize ( cur=cur@entry=0x7ffff7ffbc00 , strval=strval@entry=0x7fffffffe2c9 "2", len=len@entry=1) at dl-tunables.c:131 #2 0x00007ffff7fdb3a2 in parse_tunables (valstring=) at dl-tunables.c:258 #3 0x00007ffff7fdb5d9 in __GI___tunables_init (envp=0x7fffffffdd58) at dl-tunables.c:288 #4 0x00007ffff7fe44c3 in _dl_sysdep_start ( start_argptr=start_argptr@entry=0x7fffffffdcb0, dl_main=dl_main@entry=0x7ffff7fe5f80 ) at ../sysdeps/unix/sysv/linux/dl-sysdep.c:110 #5 0x00007ffff7fe5cae in _dl_start_final (arg=0x7fffffffdcb0) at rtld.c:494 #6 _dl_start (arg=0x7fffffffdcb0) at rtld.c:581 #7 0x00007ffff7fe4b38 in _start () (gdb) when setting GLIBC_TUNABLES in glibc compiled with APX. Reviewed-by: Florian Weimer

elf/rtld: Count skipped environment variables for enable_secure

2024-04-16T20:32:10Z

When using the glibc.rtld.enable_secure tunable we need to keep track of the count of environment variables we skip due to __libc_enable_secure being set and adjust the auxv section of the stack. This fixes an assertion when running ld.so directly with glibc.rtld.enable_secure set. Add a testcase that ensures the assert is not hit. elf/rtld.c:1324 assert (auxv == sp + 1); Reviewed-by: Adhemerval Zanella

Revert "x86_64: Suppress false positive valgrind error"

2024-04-13T15:42:13Z

This reverts commit a1735e0aa858f0c8b15e5ee9975bff4279423680. The test failure is a real valgrind bug that needs to be fixed before valgrind is usable with a glibc that has been built with CC="gcc -march=x86-64-v3". The proposed valgrind patch teaches valgrind to replace ld.so strcmp with an unoptimized scalar implementation, thus avoiding any AVX2-related problems. Valgrind bug: Reviewed-by: H.J. Lu