I reviewed the patch, and found a major bug in setting shadow_mem's
alignment.So I release patch v3.
Addition to the bug I mention,a trailing whitespace is also removed.
---
Without aligning the asan stack base,this base will only 64-bit aligned
in ARM machines.
But asan require 256-bit aligned base because of this:
1.right shift take ASAN_SHADOW_SHIFT(which is 3) bits are zeros
2.store multiple/load multiple instructions require the other 2 bits are
zeros
that add up lowest 5 bits should be zeros.That means 32 bytes or 256
bits aligned.
* asan.c (asan_emit_stack_protection): Forcing the base to align to 256
bits if STRICT_ALIGNMENT.
And set shadow_mem align to 256 bits if STRICT_ALIGNMENT
* cfgexpand.c (expand_stack_vars): set base_align appropriately when
asan is on
(expand_used_vars): Leaving a space in the stack frame for alignment if
STRICT_ALIGNMENT
---
gcc/asan.c | 10 ++++++++++
gcc/cfgexpand.c | 13 ++++++++++++-
2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/gcc/asan.c b/gcc/asan.c
index 53992a8..4389420 100644
--- a/gcc/asan.c
+++ b/gcc/asan.c
@@ -1017,8 +1017,16 @@ asan_emit_stack_protection (rtx base, rtx pbase,
unsigned int alignb,
base_align_bias = ((asan_frame_size + alignb - 1)
& ~(alignb - HOST_WIDE_INT_1)) - asan_frame_size;
}
+ /* Align base if target is STRICT_ALIGNMENT. */
+ if (STRICT_ALIGNMENT)
+ base = expand_binop (Pmode, and_optab, base,
+ gen_int_mode (-((GET_MODE_ALIGNMENT (SImode) << ASAN_SHADOW_SHIFT) /
BITS_PER_UNIT), Pmode),
+ NULL_RTX, 1, OPTAB_DIRECT);
+
if (use_after_return_class == -1 && pbase)
emit_move_insn (pbase, base);
+
+
base = expand_binop (Pmode, add_optab, base,
gen_int_mode (base_offset - base_align_bias, Pmode),
NULL_RTX, 1, OPTAB_DIRECT);
@@ -1097,6 +1105,8 @@ asan_emit_stack_protection (rtx base, rtx pbase,
unsigned int alignb,
&& (ASAN_RED_ZONE_SIZE >> ASAN_SHADOW_SHIFT) == 4);
shadow_mem = gen_rtx_MEM (SImode, shadow_base);
set_mem_alias_set (shadow_mem, asan_shadow_set);
+ if (STRICT_ALIGNMENT)
+ set_mem_align(shadow_mem, (GET_MODE_ALIGNMENT (SImode)));
prev_offset = base_offset;
for (l = length; l; l -= 2)
{
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 06d494c..14fd1c2 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -1013,10 +1013,18 @@ expand_stack_vars (bool (*pred) (size_t), struct
stack_vars_data *data)
if (data->asan_base == NULL)
data->asan_base = gen_reg_rtx (Pmode);
base = data->asan_base;
+
+ if (!STRICT_ALIGNMENT)
+ base_align = crtl->max_used_stack_slot_alignment;
+ else
+ base_align = MAX(crtl->max_used_stack_slot_alignment,
+ (GET_MODE_ALIGNMENT (SImode) << ASAN_SHADOW_SHIFT));
}
else
+ {
offset = alloc_stack_frame_space (stack_vars[i].size, alignb);
- base_align = crtl->max_used_stack_slot_alignment;
+ base_align = crtl->max_used_stack_slot_alignment;
+ }
}
else
{
@@ -1843,6 +1851,9 @@ expand_used_vars (void)
= alloc_stack_frame_space (redzonesz, ASAN_RED_ZONE_SIZE);
data.asan_vec.safe_push (prev_offset);
data.asan_vec.safe_push (offset);
+ /* Leave a space for alignment if STRICT_ALIGNMENT. */
+ if (STRICT_ALIGNMENT)
+ alloc_stack_frame_space ((GET_MODE_ALIGNMENT (SImode) <<
ASAN_SHADOW_SHIFT) / BITS_PER_UNIT , 1);
var_end_seq
= asan_emit_stack_protection (virtual_stack_vars_rtx,
--
1.8.3.2
