elf: Fix runtime linker auditing on aarch64 (BZ #26643)

The rtld audit support show two problems on aarch64:

  1. _dl_runtime_resolve does not preserve x8, the indirect result
      location register, which might generate wrong result calls
      depending of the function signature.

  2. The NEON Q registers pushed onto the stack by _dl_runtime_resolve
     were twice the size of D registers extracted from the stack frame by
     _dl_runtime_profile.

While 2. might result in wrong information passed on the PLT tracing,
1. generates wrong runtime behaviour.

The aarch64 rtld audit support is changed to:

  * Both La_aarch64_regs and La_aarch64_retval are expanded to include
    both x8 and the full sized NEON V registers, as defined by the
    ABI.

  * dl_runtime_profile needed to extract registers saved by
    _dl_runtime_resolve and put them into the new correctly sized
    La_aarch64_regs structure.

  * The LAV_CURRENT check is change to only accept new audit modules
    to avoid the undefined behavior of not save/restore x8.

  * Different than other architectures, audit modules older than
    LAV_CURRENT are rejected (both La_aarch64_regs and La_aarch64_retval
    changed their layout and there are no requirements to support multiple
    audit interface with the inherent aarch64 issues).

  * A new field is also reserved on both La_aarch64_regs and
    La_aarch64_retval to support variant pcs symbols.

Similar to x86, a new La_aarch64_vector type to represent the NEON
register is added on the La_aarch64_regs (so each type can be accessed
directly).

Since LAV_CURRENT was already bumped to support bind-now, there is
no need to increase it again.

Checked on aarch64-linux-gnu.

Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/elf/rtld.c b/elf/rtld.c
index 10436f7..8dafaf6 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -52,6 +52,7 @@
 #include <get-dynamic-info.h>
 #include <dl-execve.h>
 #include <dl-find_object.h>
+#include <dl-audit-check.h>
 
 #include <assert.h>
 
@@ -1000,7 +1001,7 @@ file=%s [%lu]; audit interface function la_version returned zero; ignored.\n",
       return;
     }
 
-  if (lav > LAV_CURRENT)
+  if (!_dl_audit_check_version (lav))
     {
       _dl_debug_printf ("\
 ERROR: audit interface '%s' requires version %d (maximum supported version %d); ignored.\n",