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Fix PR64242 - Longjmp expansion incorrect 

Improve the fix for PR64242.  Various optimizations can change a memory
reference into a frame access.  Given there are multiple virtual frame pointers
which may be replaced by multiple hard frame pointers, there are no checks for
writes to the various frame pointers.  So updates to a frame pointer tends to
generate incorrect code.  Improve the previous fix to also add clobbers of
several frame pointers and add a scheduling barrier.  This should work in most
cases until GCC supports a generic "don't optimize across this instruction"
feature.

Bootstrap OK. Testcase passes on AArch64 and x86-64.  Inspected x86, Arm,
Thumb-1 and Thumb-2 assembler which looks correct. 

    gcc/
	PR middle-end/64242
	* builtins.c (expand_builtin_longjmp): Add frame clobbers and schedule
	block.
	(expand_builtin_nonlocal_goto): Likewise.

    testsuite/
	PR middle-end/64242
	* gcc.c-torture/execute/pr64242.c: Update test.

From-SVN: r271870
This commit is contained in:
Wilco Dijkstra 2019-06-03 13:55:15 +00:00 committed by Wilco Dijkstra
parent b07fc91cc4
commit 511ed59d0b
4 changed files with 35 additions and 28 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2019-06-03 Wilco Dijkstra <wdijkstr@arm.com>
PR middle-end/64242
* builtins.c (expand_builtin_longjmp): Add frame clobbers and schedule
block.
(expand_builtin_nonlocal_goto): Likewise.
2019-06-03 Szabolcs Nagy <szabolcs.nagy@arm.com>
* config/aarch64/aarch64-protos.h (aarch64_asm_output_alias): Declare.

18
gcc/builtins.c
View File

@ -1137,15 +1137,20 @@ expand_builtin_longjmp (rtx buf_addr, rtx value)
emit_insn (targetm.gen_nonlocal_goto (value, lab, stack, fp));
else
{
lab = copy_to_reg (lab);
emit_clobber (gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (VOIDmode)));
emit_clobber (gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx));
lab = copy_to_reg (lab);
/* Restore the frame pointer and stack pointer. We must use a
temporary since the setjmp buffer may be a local. */
fp = copy_to_reg (fp);
emit_stack_restore (SAVE_NONLOCAL, stack);
/* Ensure the frame pointer move is not optimized. */
emit_insn (gen_blockage ());
emit_clobber (hard_frame_pointer_rtx);
emit_clobber (frame_pointer_rtx);
emit_move_insn (hard_frame_pointer_rtx, fp);
emit_use (hard_frame_pointer_rtx);
@ -1284,15 +1289,20 @@ expand_builtin_nonlocal_goto (tree exp)
emit_insn (targetm.gen_nonlocal_goto (const0_rtx, r_label, r_sp, r_fp));
else
{
r_label = copy_to_reg (r_label);
emit_clobber (gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (VOIDmode)));
emit_clobber (gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx));
r_label = copy_to_reg (r_label);
/* Restore the frame pointer and stack pointer. We must use a
temporary since the setjmp buffer may be a local. */
r_fp = copy_to_reg (r_fp);
emit_stack_restore (SAVE_NONLOCAL, r_sp);
/* Ensure the frame pointer move is not optimized. */
emit_insn (gen_blockage ());
emit_clobber (hard_frame_pointer_rtx);
emit_clobber (frame_pointer_rtx);
emit_move_insn (hard_frame_pointer_rtx, r_fp);
/* USE of hard_frame_pointer_rtx added for consistency;

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2019-06-03 Wilco Dijkstra <wdijkstr@arm.com>
PR middle-end/64242
* gcc.c-torture/execute/pr64242.c: Update test.
2019-06-03 Szabolcs Nagy <szabolcs.nagy@arm.com>
* gcc.target/aarch64/pcs_attribute-2.c: New test.

33
gcc/testsuite/gcc.c-torture/execute/pr64242.c
View File

@ -5,46 +5,31 @@ extern void abort (void);
__attribute ((noinline)) void
broken_longjmp (void *p)
{
void *buf[5];
void *buf[32];
__builtin_memcpy (buf, p, 5 * sizeof (void*));
/* Corrupts stack pointer... */
__builtin_longjmp (buf, 1);
}
__attribute ((noipa)) __UINTPTR_TYPE__
foo (void *p)
{
return (__UINTPTR_TYPE__) p;
}
__attribute ((noipa)) void
bar (void *p)
{
asm volatile ("" : : "r" (p));
}
volatile int x = 0;
void *volatile p;
void *volatile q;
char *volatile p;
char *volatile q;
int
main ()
{
void *buf[5];
struct __attribute__((aligned (32))) S { int a[4]; } s;
bar (&s);
p = __builtin_alloca (x);
q = __builtin_alloca (x);
if (!__builtin_setjmp (buf))
broken_longjmp (buf);
/* Compute expected next alloca offset - some targets don't align properly
and allocate too much. */
p = q + (q - p);
/* Fails if stack pointer corrupted. */
q = __builtin_alloca (x);
if (foo (p) < foo (q))
{
if (foo (q) - foo (p) >= 1024)
abort ();
}
else if (foo (p) - foo (q) >= 1024)
if (p != __builtin_alloca (x))
abort ();
return 0;