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, 17 insertions, 9 deletions

diff --git a/sysdeps/aarch64/bits/link.h b/sysdeps/aarch64/bits/link.h
index e64f36d3f3..2479abc4fb 100644
--- a/sysdeps/aarch64/bits/link.h
+++ b/sysdeps/aarch64/bits/link.h
@@ -20,23 +20,31 @@
 # error "Never include <bits/link.h> directly; use <link.h> instead."
 #endif
 
+typedef union
+{
+  float s;
+  double d;
+  long double q;
+} La_aarch64_vector;
+
 /* Registers for entry into PLT on AArch64.  */
 typedef struct La_aarch64_regs
 {
-  uint64_t lr_xreg[8];
-  uint64_t lr_dreg[8];
-  uint64_t lr_sp;
-  uint64_t lr_lr;
+  uint64_t          lr_xreg[9];
+  La_aarch64_vector lr_vreg[8];
+  uint64_t          lr_sp;
+  uint64_t          lr_lr;
+  void              *lr_vpcs;
 } La_aarch64_regs;
 
 /* Return values for calls from PLT on AArch64.  */
 typedef struct La_aarch64_retval
 {
-  /* Up to two integer registers can be used for a return value.  */
-  uint64_t lrv_xreg[2];
-  /* Up to four D registers can be used for a return value.  */
-  uint64_t lrv_dreg[4];
-
+  /* Up to eight integer registers can be used for a return value.  */
+  uint64_t          lrv_xreg[8];
+  /* Up to eight V registers can be used for a return value.  */
+  La_aarch64_vector lrv_vreg[8];
+  void              *lrv_vpcs;
 } La_aarch64_retval;
 __BEGIN_DECLS