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* [Bug tdep/30010] New: [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case)
@ 2023-01-17 13:24 vries at gcc dot gnu.org
2023-01-19 11:13 ` [Bug tdep/30010] " vries at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: vries at gcc dot gnu.org @ 2023-01-17 13:24 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=30010
Bug ID: 30010
Summary: [gdb/tdep, aarch64] Incorrect frame address for last
insn (non-leaf case)
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: tdep
Assignee: unassigned at sourceware dot org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
[ Spinoff from PR29721. ]
Consider the following test-case:
...
$ cat test.c
void
foo (const char *s)
{
}
int
main (void)
{
foo ("foo");
return 0;
}
...
Compiled without debug info:
...
$ gcc test.c
...
Disassembly of main:
...
0000000000400578 <main>:
400578: a9bf7bfd stp x29, x30, [sp, #-16]!
40057c: 910003fd mov x29, sp
400580: 90000000 adrp x0, 400000 <_init-0x408>
400584: 91192000 add x0, x0, #0x648
400588: 97fffff7 bl 400564 <foo>
40058c: 52800000 mov w0, #0x0 // #0
400590: a8c17bfd ldp x29, x30, [sp], #16
400594: d65f03c0 ret
...
Now, let's do "info frame" at each insn in main (so, using ni to skip over
foo), as well as printing $sp and $fp:
...
$ gdb a.out
Reading symbols from a.out...
(gdb) b *main
Breakpoint 1 at 0x400578
(gdb) r
Starting program: a.out
Breakpoint 1, 0x0000000000400578 in main ()
(gdb) display /x $sp
1: /x $sp = 0xfffffffff3b0
(gdb) display /x $fp
2: /x $fp = 0xfffffffff3b0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x400578 in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3b0, args:
Locals at 0xfffffffff3b0, Previous frame's sp is 0xfffffffff3b0
(gdb) ni
0x000000000040057c in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x40057c in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x0000000000400580 in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x400580 in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x0000000000400584 in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x400584 in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x0000000000400588 in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x400588 in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x000000000040058c in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x40058c in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x0000000000400590 in main ()
1: /x $sp = 0xfffffffff3a0
2: /x $fp = 0xfffffffff3a0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3b0:
pc = 0x400590 in main; saved pc = 0xfffff7e5bfa0
Arglist at 0xfffffffff3a0, args:
Locals at 0xfffffffff3a0, Previous frame's sp is 0xfffffffff3b0
Saved registers:
x29 at 0xfffffffff3a0, x30 at 0xfffffffff3a8
(gdb) ni
0x0000000000400594 in main ()
1: /x $sp = 0xfffffffff3b0
2: /x $fp = 0xfffffffff3b0
(gdb) info frame
Stack level 0, frame at 0xfffffffff3c0:
pc = 0x400594 in main; saved pc = 0x4004a4
Arglist at 0xfffffffff3b0, args:
Locals at 0xfffffffff3b0, Previous frame's sp is 0xfffffffff3c0
Saved registers:
x29 at 0xfffffffff3b0, x30 at 0xfffffffff3b8
(gdb) ni
0x0000fffff7e5bfa0 in __libc_start_main () from /lib64/libc.so.6
1: /x $sp = 0xfffffffff3b0
2: /x $fp = 0xfffffffff3b0
...
The "frame at" bit lists 0xfffffffff3b0 except at the last insn.
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 == fp and
cache->framesize == 16, so unwound_fp + cache->framesize gives the wrong answer
once fp has been restored to entry value by the before-last insn.
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* [Bug tdep/30010] [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case)
2023-01-17 13:24 [Bug tdep/30010] New: [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case) vries at gcc dot gnu.org
@ 2023-01-19 11:13 ` vries at gcc dot gnu.org
2023-01-23 15:49 ` cvs-commit at gcc dot gnu.org
2023-01-23 15:53 ` vries at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: vries at gcc dot gnu.org @ 2023-01-19 11:13 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=30010
--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Proposed patch to trigger this PR in test-case
gdb.base/unwind-on-each-insn.exp:
https://sourceware.org/pipermail/gdb-patches/2023-January/195923.html
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tdep/30010] [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case)
2023-01-17 13:24 [Bug tdep/30010] New: [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case) vries at gcc dot gnu.org
2023-01-19 11:13 ` [Bug tdep/30010] " vries at gcc dot gnu.org
@ 2023-01-23 15:49 ` cvs-commit at gcc dot gnu.org
2023-01-23 15:53 ` vries at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2023-01-23 15:49 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=30010
--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by 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
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tdep/30010] [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case)
2023-01-17 13:24 [Bug tdep/30010] New: [gdb/tdep, aarch64] Incorrect frame address for last insn (non-leaf case) vries at gcc dot gnu.org
2023-01-19 11:13 ` [Bug tdep/30010] " vries at gcc dot gnu.org
2023-01-23 15:49 ` cvs-commit at gcc dot gnu.org
@ 2023-01-23 15:53 ` vries at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: vries at gcc dot gnu.org @ 2023-01-23 15:53 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=30010
Tom de Vries <vries at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |14.1
Resolution|--- |FIXED
Status|NEW |RESOLVED
--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Fixed by commit.
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