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2011-02-15 Yao Qi <yao@codesourcery.com>

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PR tdep/12352
	* arm-tdep.c (copy_ldr_str_ldrb_strb): Replace PC with SP in
	order to store PC value on stack instead of text section.

2011-02-15  Yao Qi  <yao@codesourcery.com>

	PR tdep/12352
	* gdb.arch/arm-disp-step.S : New test for str instruction.
	* gdb.arch/arm-disp-step.exp : Likewise
This commit is contained in:
Yao Qi
2011-02-15 14:26:34 +00:00
parent d9492458a1
commit 494e194e77
5 changed files with 104 additions and 11 deletions
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29
gdb/arm-tdep.c
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@ -5930,16 +5930,24 @@ copy_ldr_str_ldrb_strb (struct gdbarch *gdbarch, uint32_t insn,
/* To write PC we can do:
scratch+0: str pc, temp (*temp = scratch + 8 + offset)
scratch+4: ldr r4, temp
scratch+8: sub r4, r4, pc (r4 = scratch + 8 + offset - scratch - 8 - 8)
scratch+12: add r4, r4, #8 (r4 = offset)
scratch+16: add r0, r0, r4
scratch+20: str r0, [r2, #imm] (or str r0, [r2, r3])
scratch+24: <temp>
Before this sequence of instructions:
r0 is the PC value got from displaced_read_reg, so r0 = from + 8;
r2 is the Rn value got from dispalced_read_reg.
Insn1: push {pc} Write address of STR instruction + offset on stack
Insn2: pop {r4} Read it back from stack, r4 = addr(Insn1) + offset
Insn3: sub r4, r4, pc r4 = addr(Insn1) + offset - pc
= addr(Insn1) + offset - addr(Insn3) - 8
= offset - 16
Insn4: add r4, r4, #8 r4 = offset - 8
Insn5: add r0, r0, r4 r0 = from + 8 + offset - 8
= from + offset
Insn6: str r0, [r2, #imm] (or str r0, [r2, r3])
Otherwise we don't know what value to write for PC, since the offset is
architecture-dependent (sometimes PC+8, sometimes PC+12). */
architecture-dependent (sometimes PC+8, sometimes PC+12). More details
of this can be found in Section "Saving from r15" in
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0204g/Cihbjifh.html */
if (load || rt != 15)
{
@ -5960,9 +5968,8 @@ copy_ldr_str_ldrb_strb (struct gdbarch *gdbarch, uint32_t insn,
{
/* We need to use r4 as scratch. Make sure it's restored afterwards. */
dsc->u.ldst.restore_r4 = 1;
dsc->modinsn[0] = 0xe58ff014; /* str pc, [pc, #20]. */
dsc->modinsn[1] = 0xe59f4010; /* ldr r4, [pc, #16]. */
dsc->modinsn[0] = 0xe92d8000; /* push {pc} */
dsc->modinsn[1] = 0xe8bd0010; /* pop {r4} */
dsc->modinsn[2] = 0xe044400f; /* sub r4, r4, pc. */
dsc->modinsn[3] = 0xe2844008; /* add r4, r4, #8. */
dsc->modinsn[4] = 0xe0800004; /* add r0, r0, r4. */