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Update trap/break handling in nios2 prologue analyzer.

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2015-07-30  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/
	* nios2-tdep.c (nios2_analyze_prologue): Update comments to
	reflect how current GCC emits stack overflow checks.  Match
	both trap and break instructions for backward compatibility.
	Disallow other trap and break instructions in the prologue.
This commit is contained in:
Sandra Loosemore 2015-07-30 13:23:43 -07:00
parent 61a934ca20
commit 9aaf8e3a28
2 changed files with 32 additions and 14 deletions
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7
gdb/ChangeLog
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@ -1,3 +1,10 @@
2015-07-30 Sandra Loosemore <sandra@codesourcery.com>
* nios2-tdep.c (nios2_analyze_prologue): Update comments to
reflect how current GCC emits stack overflow checks. Match
both trap and break instructions for backward compatbility.
Disallow other trap and break instructions in the prologue.
2015-07-30 Pedro Alves <palves@redhat.com>
PR threads/18600

39
gdb/nios2-tdep.c
View File

@ -697,22 +697,29 @@ nios2_stack_frame_destroyed_p (struct gdbarch *gdbarch, CORE_ADDR pc)
stw sp, constant(rx)
mov sp, rx
5) A frame pointer save, which can be either a MOV or ADDI.
4) A frame pointer save, which can be either a MOV or ADDI.
6) A further stack pointer adjustment. This is normally included
adjustment in step 4 unless the total adjustment is too large
5) A further stack pointer adjustment. This is normally included
adjustment in step 3 unless the total adjustment is too large
to be done in one step.
7) A stack overflow check, which can take either of these forms:
bgeu sp, rx, +8
break 3
trap 3
or
bltu sp, rx, .Lstack_overflow
...
.Lstack_overflow:
break 3
If present, this is inserted after the stack pointer adjustments
for steps 3, 4, and 6.
trap 3
Older versions of GCC emitted "break 3" instead of "trap 3" here,
so we check for both cases.
Older GCC versions emitted stack overflow checks after the SP
adjustments in both steps 3 and 4. Starting with GCC 6, there is
at most one overflow check, which is placed before the first
stack adjustment for R2 CDX and after the first stack adjustment
otherwise.
The prologue instructions may be combined or interleaved with other
instructions.
@ -995,14 +1002,15 @@ nios2_analyze_prologue (struct gdbarch *gdbarch, const CORE_ADDR start_pc,
else if (cond == branch_geu)
{
/* BGEU sp, rx, +8
BREAK 3
TRAP 3 (or BREAK 3)
This instruction sequence is used in stack checking;
we can ignore it. */
unsigned int next_insn;
const struct nios2_opcode *next_op
= nios2_fetch_insn (gdbarch, pc, &next_insn);
if (next_op != NULL
&& nios2_match_break (next_insn, op, mach, &uimm))
&& (nios2_match_trap (next_insn, op, mach, &uimm)
|| nios2_match_break (next_insn, op, mach, &uimm)))
pc += next_op->size;
else
break;
@ -1010,13 +1018,14 @@ nios2_analyze_prologue (struct gdbarch *gdbarch, const CORE_ADDR start_pc,
else if (cond == branch_ltu)
{
/* BLTU sp, rx, .Lstackoverflow
If the location branched to holds a BREAK 3 instruction
then this is also stack overflow detection. */
If the location branched to holds a TRAP or BREAK
instruction then this is also stack overflow detection. */
unsigned int next_insn;
const struct nios2_opcode *next_op
= nios2_fetch_insn (gdbarch, pc + imm, &next_insn);
if (next_op != NULL
&& nios2_match_break (next_insn, op, mach, &uimm))
&& (nios2_match_trap (next_insn, op, mach, &uimm)
|| nios2_match_break (next_insn, op, mach, &uimm)))
;
else
break;
@ -1025,11 +1034,13 @@ nios2_analyze_prologue (struct gdbarch *gdbarch, const CORE_ADDR start_pc,
break;
}
/* All other calls or jumps (including returns) terminate
/* All other calls, jumps, returns, TRAPs, or BREAKs terminate
the prologue. */
else if (nios2_match_callr (insn, op, mach, &ra)
|| nios2_match_jmpr (insn, op, mach, &ra)
|| nios2_match_jmpi (insn, op, mach, &uimm))
|| nios2_match_jmpi (insn, op, mach, &uimm)
|| nios2_match_trap (insn, op, mach, &uimm)
|| nios2_match_break (insn, op, mach, &uimm))
break;
}