[binutils-gdb] [gdb/tdep, aarch64] Fix frame address of last insn

[Tom de Vries <vries@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=29e09a42f1d1af3d97652e54b6b3cac68cf61d15

commit 29e09a42f1d1af3d97652e54b6b3cac68cf61d15
Author: Tom de Vries <tdevries@suse.de>
Date:   Mon Jan 23 16:49:36 2023 +0100

    [gdb/tdep, aarch64] Fix frame address of last insn
    
    Consider the test-case test.c, compiled without debug info:
    ...
    void
    foo (const char *s)
    {
    }
    
    int
    main (void)
    {
      foo ("foo");
      return 0;
    }
    ...
    
    Disassembly of foo:
    ...
    0000000000400564 <foo>:
      400564:       d10043ff        sub     sp, sp, #0x10
      400568:       f90007e0        str     x0, [sp, #8]
      40056c:       d503201f        nop
      400570:       910043ff        add     sp, sp, #0x10
      400574:       d65f03c0        ret
    ...
    
    Now, let's do "info frame" at each insn in foo, as well as printing $sp
    and $x29 (and strip the output of info frame to the first line, for brevity):
    ...
    $ gdb -q a.out
    Reading symbols from a.out...
    (gdb) b *foo
    Breakpoint 1 at 0x400564
    (gdb) r
    Starting program: a.out
    
    Breakpoint 1, 0x0000000000400564 in foo ()
    (gdb) display /x $sp
    1: /x $sp = 0xfffffffff3a0
    (gdb) display /x $x29
    2: /x $x29 = 0xfffffffff3a0
    (gdb) info frame
    Stack level 0, frame at 0xfffffffff3a0:
    (gdb) si
    0x0000000000400568 in foo ()
    1: /x $sp = 0xfffffffff390
    2: /x $x29 = 0xfffffffff3a0
    (gdb) info frame
    Stack level 0, frame at 0xfffffffff3a0:
    (gdb) si
    0x000000000040056c in foo ()
    1: /x $sp = 0xfffffffff390
    2: /x $x29 = 0xfffffffff3a0
    (gdb) info frame
    Stack level 0, frame at 0xfffffffff3a0:
    (gdb) si
    0x0000000000400570 in foo ()
    1: /x $sp = 0xfffffffff390
    2: /x $x29 = 0xfffffffff3a0
    (gdb) info frame
    Stack level 0, frame at 0xfffffffff3a0:
    (gdb) si
    0x0000000000400574 in foo ()
    1: /x $sp = 0xfffffffff3a0
    2: /x $x29 = 0xfffffffff3a0
    (gdb) info frame
    Stack level 0, frame at 0xfffffffff3b0:
     pc = 0x400574 in foo; saved pc = 0x40058c
    (gdb) si
    0x000000000040058c in main ()
    1: /x $sp = 0xfffffffff3a0
    2: /x $x29 = 0xfffffffff3a0
    ...
    
    The "frame at" bit lists 0xfffffffff3a0 except at the last insn, where it
    lists 0xfffffffff3b0.
    
    The frame address is calculated here in aarch64_make_prologue_cache_1:
    ...
      unwound_fp = get_frame_register_unsigned (this_frame, cache->framereg);
      if (unwound_fp == 0)
        return;
    
      cache->prev_sp = unwound_fp + cache->framesize;
    ...
    
    For insns after the prologue, we have cache->framereg == sp and
    cache->framesize == 16, so unwound_fp + cache->framesize gives the wrong
    answer once sp has been restored to entry value by the before-last insn.
    
    Fix this by detecting the situation that the sp has been restored.
    
    This fixes PRs tdep/30010 and tdep/30011.
    
    This also fixes the aarch64 FAILs in gdb.reverse/solib-precsave.exp and
    gdb.reverse/solib-reverse.exp I reported in PR gdb/PR29721.
    
    Tested on aarch64-linux.
    PR tdep/30010
    PR tdep/30011
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30010
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30011

Diff:
---
 gdb/aarch64-tdep.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index aeca30587a5..ea93e9ad0d2 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -149,6 +149,8 @@ static const char *const aarch64_mte_register_names[] =
   "tag_ctl"
 };
 
+static int aarch64_stack_frame_destroyed_p (struct gdbarch *, CORE_ADDR);
+
 /* AArch64 prologue cache structure.  */
 struct aarch64_prologue_cache
 {
@@ -1000,7 +1002,10 @@ aarch64_make_prologue_cache_1 (frame_info_ptr this_frame,
   if (unwound_fp == 0)
     return;
 
-  cache->prev_sp = unwound_fp + cache->framesize;
+  cache->prev_sp = unwound_fp;
+  if (!aarch64_stack_frame_destroyed_p (get_frame_arch (this_frame),
+					cache->prev_pc))
+    cache->prev_sp += cache->framesize;
 
   /* Calculate actual addresses of saved registers using offsets
      determined by aarch64_analyze_prologue.  */