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, 103 insertions, 0 deletions

diff --git a/sysdeps/aarch64/tst-auditmod26.c b/sysdeps/aarch64/tst-auditmod26.c
new file mode 100644
index 0000000000..b03b6baed9
--- /dev/null
+++ b/sysdeps/aarch64/tst-auditmod26.c
@@ -0,0 +1,103 @@
+/* Check LD_AUDIT for aarch64 specific ABI.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <link.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "tst-audit26mod.h"
+
+#define TEST_NAME  "tst-audit26"
+
+#define AUDIT26_COOKIE 0
+
+unsigned int
+la_version (unsigned int v)
+{
+  return v;
+}
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t *cookie)
+{
+  const char *p = strrchr (map->l_name, '/');
+  const char *l_name = p == NULL ? map->l_name : p + 1;
+  uintptr_t ck = -1;
+  if (strncmp (l_name, TEST_NAME, strlen (TEST_NAME)) == 0)
+    ck = AUDIT26_COOKIE;
+  *cookie = ck;
+  printf ("objopen: %ld, %s [cookie=%ld]\n", lmid, l_name, ck);
+  return ck == -1 ? 0 : LA_FLG_BINDFROM | LA_FLG_BINDTO;
+}
+
+ElfW(Addr)
+la_aarch64_gnu_pltenter (ElfW(Sym) *sym __attribute__ ((unused)),
+                         unsigned int ndx __attribute__ ((unused)),
+                         uintptr_t *refcook, uintptr_t *defcook,
+                         La_aarch64_regs *regs, unsigned int *flags,
+                         const char *symname, long int *framesizep)
+{
+  printf ("pltenter: symname=%s, st_value=%#lx, ndx=%u, flags=%u\n",
+	  symname, (long int) sym->st_value, ndx, *flags);
+
+  if (strcmp (symname, "tst_audit26_func") == 0)
+    {
+      assert (regs->lr_xreg[0] == ARG1);
+      assert (regs->lr_xreg[1] == ARG2);
+      assert (regs->lr_xreg[2] == ARG3);
+    }
+  else
+    abort ();
+
+  assert (regs->lr_vpcs == 0);
+
+  /* Clobber 'x8'.  */
+  asm volatile ("mov x8, -1" : : : "x8");
+
+  *framesizep = 1024;
+
+  return sym->st_value;
+}
+
+unsigned int
+la_aarch64_gnu_pltexit (ElfW(Sym) *sym, unsigned int ndx, uintptr_t *refcook,
+                        uintptr_t *defcook,
+                        const struct La_aarch64_regs *inregs,
+                        struct La_aarch64_retval *outregs, const char *symname)
+{
+  printf ("pltexit: symname=%s, st_value=%#lx, ndx=%u\n",
+	  symname, (long int) sym->st_value, ndx);
+
+  if (strcmp (symname, "tst_audit26_func") == 0)
+    {
+      assert (inregs->lr_xreg[0] == ARG1);
+      assert (inregs->lr_xreg[1] == ARG2);
+      assert (inregs->lr_xreg[2] == ARG3);
+    }
+  else
+    abort ();
+
+  assert (inregs->lr_vpcs == 0);
+  assert (outregs->lrv_vpcs == 0);
+
+  /* Clobber 'x8'.  */
+  asm volatile ("mov x8, -1" : : : "x8");
+
+  return 0;
+}