From: Tom de Vries <tdevries@suse.de>
To: gdb-patches@sourceware.org
Cc: Bruno Larsen <blarsen@redhat.com>,
Andrew Burgess <aburgess@redhat.com>,
Luis Machado <luis.machado@arm.com>
Subject: [PATCH 3/4] [gdb/tdep, aarch64] Fix frame address of last insn in leaf function
Date: Thu, 19 Jan 2023 11:46:17 +0100 [thread overview]
Message-ID: <20230119104618.15503-4-tdevries@suse.de> (raw)
In-Reply-To: <20230119104618.15503-1-tdevries@suse.de>
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 PR 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/30011
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30011
---
gdb/aarch64-tdep.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index b576d3b9d99..06349353716 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -996,7 +996,11 @@ aarch64_make_prologue_cache_1 (frame_info_ptr this_frame,
if (unwound_fp == 0)
return;
- cache->prev_sp = unwound_fp + cache->framesize;
+ if (cache->framereg == AARCH64_SP_REGNUM
+ && get_frame_register_unsigned (this_frame, AARCH64_FP_REGNUM) == unwound_fp)
+ cache->prev_sp = unwound_fp;
+ else
+ cache->prev_sp = unwound_fp + cache->framesize;
/* Calculate actual addresses of saved registers using offsets
determined by aarch64_analyze_prologue. */
--
2.35.3
next prev parent reply other threads:[~2023-01-19 10:46 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-19 10:46 [PATCH 0/4] [gdb] Test-case gdb.base/unwind-on-each-insn.exp improvements Tom de Vries
2023-01-19 10:46 ` [PATCH 1/4] [gdb/testsuite] Simplify gdb.base/unwind-on-each-insn.exp Tom de Vries
2023-01-23 9:36 ` Tom de Vries
2023-01-19 10:46 ` [PATCH 2/4] [gdb/testsuite] Improve gdb.base/unwind-on-each-insn.exp Tom de Vries
2023-01-23 9:55 ` Luis Machado
2023-01-19 10:46 ` Tom de Vries [this message]
2023-01-20 10:25 ` [PATCH 3/4] [gdb/tdep, aarch64] Fix frame address of last insn in leaf function Tom de Vries
2023-01-23 10:07 ` Luis Machado
2023-01-23 11:59 ` Tom de Vries
2023-01-23 12:09 ` Luis Machado
2023-01-19 10:46 ` [PATCH 4/4] [gdb/testsuite] Analyze non-leaf fn in gdb.base/unwind-on-each-insn.exp Tom de Vries
2023-01-23 10:18 ` Luis Machado
2023-01-25 12:32 ` [PATCH 0/4] [gdb] Test-case gdb.base/unwind-on-each-insn.exp improvements Tom de Vries
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