On Mon, Jun 01, 2020 at 02:28:51PM +0200, Martin Liška wrote:
> --- a/gcc/asan.c
> +++ b/gcc/asan.c
> @@ -1598,8 +1598,24 @@ asan_emit_stack_protection (rtx base, rtx pbase,
> unsigned int alignb,
> if (use_after_return_class < 5
> && can_store_by_pieces (sz, builtin_memset_read_str, &c,
> BITS_PER_UNIT, true))
> - store_by_pieces (shadow_mem, sz, builtin_memset_read_str, &c,
> - BITS_PER_UNIT, true, RETURN_BEGIN);
> + {
> + /* Emit:
> + memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
> + **SavedFlagPtr(FakeStack) = 0
> + */
> + store_by_pieces (shadow_mem, sz, builtin_memset_read_str, &c,
> + BITS_PER_UNIT, true, RETURN_BEGIN);
> +
> + unsigned HOST_WIDE_INT offset
> + = (1 << (use_after_return_class + 6));
> + offset -= GET_MODE_SIZE (ptr_mode);
> + mem = adjust_address (mem, Pmode, offset);
> + mem = gen_rtx_MEM (ptr_mode, mem);
> + rtx tmp_reg = gen_reg_rtx (Pmode);
> + emit_move_insn (tmp_reg, mem);
> + mem = adjust_address (mem, QImode, 0);
> + emit_move_insn (mem, const0_rtx);
This doesn't look correct to me.
I'd think the first adjust_address should be
mem = adjust_address (mem, ptr_mode, offset);
which will give you a MEM with ptr_mode which has SavedFlagPtr(FakeStack)
address, i.e. *SavedFlagPtr(FakeStack).
Next, you want to load that into some temporary, so e.g.
rtx addr = gen_reg_rtx (ptr_mode);
emit_move_insn (addr, mem);
next you need to convert that ptr_mode to Pmode if needed, so something like
addr = convert_memory_address (Pmode, addr);
and finally:
mem = gen_rtx_MEM (QImode, addr);
emit_move_insn (mem, const0_rtx);
Completely untested.
Jakub
