gdb/testsuite/gdb.arch/riscv64-unwind-prologue-with-ld-lw-foo.s

   1 /* Copyright 2021-2023 Free Software Foundation, Inc.
   2
   3    This program is free software; you can redistribute it and/or modify
   4    it under the terms of the GNU General Public License as published by
   5    the Free Software Foundation; either version 3 of the License, or
   6    (at your option) any later version.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11    GNU General Public License for more details.
  12
  13    You should have received a copy of the GNU General Public License
  14    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  15
  16 /* This testcase contains a function where the 'ld', 'c.ld', 'lw' or 'c.lw'
  17    instruction is used in the prologue before the RA register have been saved
  18    on the stack.
  19
  20    This mimics a pattern observed in the __pthread_clockjoin_ex function
  21    in libpthread.so.0 (from glibc-2.33-0ubuntu5) where a canary value is
  22    loaded and placed on the stack in order to detect stack smashing.
  23
  24    The skeleton for this file was generated using the following command:
  25
  26       gcc -x c -S -c -o - - <<EOT
  27         static long int __canary = 42;
  28         extern int bar ();
  29         int foo () { return bar(); }
  30       EOT
  31
  32    The result of this command is modified in the following way:
  33      - The prologue is adapted to reserve 16 more bytes on the stack.
  34      - A part that simulates the installation of a canary on the stack is
  35        added.  The canary is loaded multiple times to simulate the use of
  36        various instructions that could do the work (ld or c.ld for a 64 bit
  37        canary, lw or c.lw for a 32 bit canary).
  38      - The epilogue is adjusted to be able to return properly.  The epilogue
  39        does not check the canary value since this testcase is only interested
  40        in ensuring GDB can scan the prologue.  */
  41
  42         .option pic
  43         .text
  44         .data
  45         .align  3
  46         .type   __canary, @object
  47         .size   __canary, 8
  48 __canary:
  49         .dword  42
  50         .text
  51         .align  1
  52         .globl  foo
  53         .type   foo, @function
  54 foo:
  55         addi    sp,sp,-32
  56         lla     a5,__canary  # Load the fake canary address.
  57         lw      t4,0(a5)     # Load a 32 bit canary (use t4 to force the use of
  58                              # the non compressed instruction).
  59         ld      t4,0(a5)     # Load a 64 bit canary (use t4 to force the use of
  60                              # the non compressed instruction).
  61         c.lw    a4,0(a5)     # Load a 32 bit canary using the compressed insn.
  62         c.ld    a4,0(a5)     # Load a 64 bit canary using the compressed insn.
  63         sd      a4,0(sp)     # Place the fake canary on the stack.
  64         sd      ra,16(sp)
  65         sd      s0,8(sp)
  66         addi    s0,sp,32
  67         call    bar@plt
  68         mv      a5,a0
  69         mv      a0,a5
  70         ld      ra,16(sp)
  71         ld      s0,8(sp)
  72         addi    sp,sp,32
  73         jr      ra
  74         .size   foo, .-foo
  75         .section        .note.GNU-stack,"",@progbits