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2022-11-03elf: Rework exception handling in the dynamic loader [BZ #25486]Florian Weimer
The old exception handling implementation used function interposition to replace the dynamic loader implementation (no TLS support) with the libc implementation (TLS support). This results in problems if the link order between the dynamic loader and libc is reversed (bug 25486). The new implementation moves the entire implementation of the exception handling functions back into the dynamic loader, using THREAD_GETMEM and THREAD_SETMEM for thread-local data support. These depends on Hurd support for these macros, added in commit b65a82e4e757c1e6cb7073916 ("hurd: Add THREAD_GET/SETMEM/_NC"). One small obstacle is that the exception handling facilities are used before the TCB has been set up, so a check is needed if the TCB is available. If not, a regular global variable is used to store the exception handling information. Also rename dl-error.c to dl-catch.c, to avoid confusion with the dlerror function. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
2021-07-22mtrace: Wean away from malloc hooksSiddhesh Poyarekar
Wean mtrace away from the malloc hooks and move them into the debug DSO. Split the API away from the implementation so that we can add the API to libc.so as well as libc_malloc_debug.so, with the libc implementations being empty. Update localplt data since memalign no longer has any callers after this change. Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@redhat.com>
2020-02-15ld.so: Do not export free/calloc/malloc/realloc functions [BZ #25486]Florian Weimer
Exporting functions and relying on symbol interposition from libc.so makes the choice of implementation dependent on DT_NEEDED order, which is not what some compiler drivers expect. This commit replaces one magic mechanism (symbol interposition) with another one (preprocessor-/compiler-based redirection). This makes the hand-over from the minimal malloc to the full malloc more explicit. Removing the ABI symbols is backwards-compatible because libc.so is always in scope, and the dynamic loader will find the malloc-related symbols there since commit f0b2132b35248c1f4a80f62a2c38cddcc802aa8c ("ld.so: Support moving versioned symbols between sonames [BZ #24741]"). Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2017-08-10ld.so: Introduce struct dl_exceptionFlorian Weimer
This commit separates allocating and raising exceptions. This simplifies catching and re-raising them because it is no longer necessary to make a temporary, on-stack copy of the exception message.
2017-03-02Document and fix --enable-bind-now [BZ #21015]Florian Weimer
2016-11-30ld.so: Remove __libc_memalignFlorian Weimer
It is no longer needed since commit 6c444ad6e953dbdf9c7be065308a0a777 (elf: Do not use memalign for TCB/TLS blocks allocation [BZ #17730]). Applications do not link against ld.so and will use the definition in libc.so, so there is no ABI impact.
2016-11-30Implement _dl_catch_error, _dl_signal_error in libc.so [BZ #16628]Florian Weimer
This change moves the main implementation of _dl_catch_error, _dl_signal_error to libc.so, where TLS variables can be used directly. This removes a writable function pointer from the rtld_global variable. For use during initial relocation, minimal implementations of these functions are provided in ld.so. These are eventually interposed by the libc.so implementations. This is implemented by compiling elf/dl-error-skeleton.c twice, via elf/dl-error.c and elf/dl-error-minimal.c. As a side effect of this change, the static version of dl-error.c no longer includes support for the _dl_signal_cerror/_dl_receive_error mechanism because it is only used in ld.so.
2015-10-14Support PLT and GOT references in local PIC checkH.J. Lu
Linker in binutils 2.26 and newer generate GOT references instead PLT references when -z now is passed to linker. We need to extend scripts/localplt.awk to allow PLT or GOT references. [BZ #19007] * scripts/localplt.awk: Also allow GOT references. * sysdeps/unix/sysv/linux/i386/localplt.data: Mark _Unwind_Find_FDE, calloc, memalign, realloc and __libc_memalign with "+ REL R_386_GLOB_DAT". * sysdeps/x86_64/localplt.data: Mark calloc, memalign, realloc and __libc_memalign with "+ RELA R_X86_64_GLOB_DAT".
2015-07-29Extend local PLT reference checkH.J. Lu
On x86, linker in binutils 2.26 and newer consolidates R_*_JUMP_SLOT with R_*_GLOB_DAT relocation against the same symbol. This patch extends local PLT reference check to support alternate relocations. [BZ #18078] * scripts/check-localplt.awk: Support alternate relocations. * scripts/localplt.awk: Also check relocations in DT_RELA/DT_REL sections. * sysdeps/unix/sysv/linux/i386/localplt.data: Mark free and malloc entries with + REL R_386_GLOB_DAT. * sysdeps/x86_64/localplt.data: New file.