gdb/gdb-tdep-fix-reverse-execution-of-ldr-immediate-t4.patch

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From b8a8f319b30149f94823302d9120d83b9eee01a4 Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Tue, 13 Feb 2024 09:10:54 +0100
Subject: [PATCH 23/48] [gdb/tdep] Fix reverse execution of LDR(immediate) T4
When running test-case gdb.reverse/func-map-to-same-line.exp on arm-linux with
target board unix/-mthumb, we run into:
...
(gdb) reverse-step
func2 () at func-map-to-same-line.c:26
26 {
(gdb) FAIL: gdb.reverse/func-map-to-same-line.exp: \
column_info_flag=column-info: step-test: reverse-step into func2
...
The FAIL is caused by incorrect recording of this insn:
...
4f6: f85d 7b04 ldr.w r7, [sp], #4
...
The insn updates the sp, but we don't record this:
...
$ gdb -q -batch func-map-to-same-line \
-ex "b *func2+8" \
-ex run \
-ex record \
-ex "set debug record 2" \
-ex stepi
Breakpoint 1 at 0x4f6: file func-map-to-same-line.c, line 27.
Breakpoint 1, 0xaaaaa4f6 in func2 () at func-map-to-same-line.c:27
27 } /* END FUNC2 */
Process record: arm_process_record addr = 0xaaaaa4f6
Process record: add register num = 15 to record list.
Process record: record_full_arch_list_add 0xabc6c460.
Process record: add register num = 7 to record list.
Process record: record_full_arch_list_add 0xabc3b868.
Process record: add register num = 25 to record list.
...
[ Note that sp is r13, and we see here only r15 (pc), r7, and r25 (ps). ]
The problem is that the specific insn, an LDR(immediate) T4, is not handled in
thumb2_record_ld_word.
Fix this by detecting the insn in thumb2_record_ld_word, and recording the
updated base register.
Tested on arm-linux.
Reported-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Approved-By: Luis Machado <luis.machado@arm.com>
PR tdep/31278
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31278
---
gdb/arm-tdep.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 04392115848..3b1682a2aea 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -14156,6 +14156,14 @@ thumb2_record_ld_word (arm_insn_decode_record *thumb2_insn_r)
record_buf[1] = ARM_PS_REGNUM;
thumb2_insn_r->reg_rec_count = 2;
+ if ((thumb2_insn_r->arm_insn & 0xfff00900) == 0xf8500900)
+ {
+ /* Detected LDR(immediate), T4, with write-back bit set. Record Rn
+ update. */
+ record_buf[2] = bits (thumb2_insn_r->arm_insn, 16, 19);
+ thumb2_insn_r->reg_rec_count++;
+ }
+
REG_ALLOC (thumb2_insn_r->arm_regs, thumb2_insn_r->reg_rec_count,
record_buf);
return ARM_RECORD_SUCCESS;
--
2.35.3