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Re: libsanitizer merge from upstream r191666
- From: Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Dodji Seketeli <dodji at redhat dot com>, Dmitry Vyukov <dvyukov at google dot com>
- Date: Thu, 14 Nov 2013 21:56:36 +0400
- Subject: Re: libsanitizer merge from upstream r191666
- Authentication-results: sourceware.org; auth=none
- References: <CAGQ9bdzrx07_OfvCcxm_uFUt3MRhg1gwqdHvmK_9kHDmz1vPVw at mail dot gmail dot com> <CAGQ9bdxj-DmEaoo0mOWfSVXsrhVShWj3onHZRxiwt97Vq6J45w at mail dot gmail dot com> <20131029121355 dot GY30970 at tucnak dot zalov dot cz> <CAGQ9bdw+VW=yF+vaqE_0GkyHUChL_vp3cABZf-FuNYoHo3g=eg at mail dot gmail dot com> <20131029135236 dot GB30970 at tucnak dot zalov dot cz> <CAGQ9bdwHhvDksRcWqn3udeDy=7xAtXueo63Km_h=To9PZ7Li8g at mail dot gmail dot com> <20131114153349 dot GC27813 at tucnak dot zalov dot cz>
On Thu, Nov 14, 2013 at 7:33 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Tue, Oct 29, 2013 at 07:05:49AM -0700, Konstantin Serebryany wrote:
>> The calls are emitted by default, but the __asan_stack_malloc call is
>> done under a run-time flag
>> __asan_option_detect_stack_use_after_return.
>> So, to use the stack-use-after-return feature you should simply
>> compile with -fsanitize=address and then at run-time
>> pass ASAN_OPTIONS=detect_stack_use_after_return=1
>> For small stack frame sizes the call to __asan_stack_free is inlined
>> (as a performance optimization, not mandatory).
>
> Ok, here is heavily untested implementation of the use after return
> sanitization. Tested just by eyeballing assembly generated for some
> testcases and on stack-use-after-return.cc and testing asan.exp (but that
> has no use-after-return tests, right?).
Nice! I haven't tried gcc-asan on heavy things for a while.
I'll try to give it a shot (first w/o this patch, then with it) on
chrome, where stack-use-after-return is known to just work.
>
> What I'm not very happy about is that __asan_stack_malloc_N doesn't have
> align argument, is there at least some guaranteed alignment on what it
> returns that gcc
I thought about alignment but did not reflect it anywhere in the
interface/comments.
The alignment should be min(4096, N), which is enough for most purposes.
But let me double-check (and add a CHECK) tomorrow.
--kcc
> can hardcode (and if the required alignment is bigger, just
> don't call __asan_stack_malloc_N)? I mean, e.g. on x86_64/i686, right now
> say for -mavx code quite often 256-bit alignment is needed, with -mavx512f
> 512-bit alignment will be needed from time to time. So if for now
> libasan could guarantee 64-byte alignment of the stack chunks or at least
> 32-byte alignment, I could pass the required alignment to
> asan_emit_stack_protection and force no __asan_stack_malloc_N use if
> the required alignment is smaller than the one guaranteed by libasan.
>
> 2013-11-14 Jakub Jelinek <jakub@redhat.com>
>
> * cfgexpand.c (struct stack_vars_data): Add asan_base field.
> (expand_stack_vars): For -fsanitize=address, use (and set initially)
> data->asan_base as base for vars.
> (expand_used_vars): Initialize data.asan_base. Pass it to
> asan_emit_stack_protection.
> * asan.c (asan_detect_stack_use_after_return): New variable.
> (asan_emit_stack_protection): Add pbase argument. Implement use
> after return sanitization.
> * asan.h (asan_emit_stack_protection): Adjust prototype.
> (ASAN_STACK_MAGIC_USE_AFTER_RET, ASAN_STACK_RETIRED_MAGIC): Define.
>
> --- gcc/cfgexpand.c.jj 2013-11-14 09:10:08.000000000 +0100
> +++ gcc/cfgexpand.c 2013-11-14 12:42:25.194538823 +0100
> @@ -879,6 +879,9 @@ struct stack_vars_data
>
> /* Vector of partition representative decls in between the paddings. */
> vec<tree> asan_decl_vec;
> +
> + /* Base pseudo register for Address Sanitizer protected automatic vars. */
> + rtx asan_base;
> };
>
> /* A subroutine of expand_used_vars. Give each partition representative
> @@ -963,6 +966,7 @@ expand_stack_vars (bool (*pred) (size_t)
> alignb = stack_vars[i].alignb;
> if (alignb * BITS_PER_UNIT <= MAX_SUPPORTED_STACK_ALIGNMENT)
> {
> + base = virtual_stack_vars_rtx;
> if ((flag_sanitize & SANITIZE_ADDRESS) && pred)
> {
> HOST_WIDE_INT prev_offset = frame_offset;
> @@ -991,10 +995,12 @@ expand_stack_vars (bool (*pred) (size_t)
> if (repr_decl == NULL_TREE)
> repr_decl = stack_vars[i].decl;
> data->asan_decl_vec.safe_push (repr_decl);
> + if (data->asan_base == NULL)
> + data->asan_base = gen_reg_rtx (Pmode);
> + base = data->asan_base;
> }
> else
> offset = alloc_stack_frame_space (stack_vars[i].size, alignb);
> - base = virtual_stack_vars_rtx;
> base_align = crtl->max_used_stack_slot_alignment;
> }
> else
> @@ -1768,6 +1774,7 @@ expand_used_vars (void)
>
> data.asan_vec = vNULL;
> data.asan_decl_vec = vNULL;
> + data.asan_base = NULL_RTX;
>
> /* Reorder decls to be protected by iterating over the variables
> array multiple times, and allocating out of each phase in turn. */
> @@ -1800,8 +1807,9 @@ expand_used_vars (void)
>
> var_end_seq
> = asan_emit_stack_protection (virtual_stack_vars_rtx,
> + data.asan_base,
> data.asan_vec.address (),
> - data.asan_decl_vec. address (),
> + data.asan_decl_vec.address (),
> data.asan_vec.length ());
> }
>
> --- gcc/asan.c.jj 2013-11-14 09:10:08.000000000 +0100
> +++ gcc/asan.c 2013-11-14 16:06:42.203713457 +0100
> @@ -226,6 +226,9 @@ alias_set_type asan_shadow_set = -1;
> alias set is used for all shadow memory accesses. */
> static GTY(()) tree shadow_ptr_types[2];
>
> +/* Decl for __asan_option_detect_stack_use_after_return. */
> +static GTY(()) tree asan_detect_stack_use_after_return;
> +
> /* Hashtable support for memory references used by gimple
> statements. */
>
> @@ -939,20 +942,25 @@ asan_function_start (void)
> and DECLS is an array of representative decls for each var partition.
> LENGTH is the length of the OFFSETS array, DECLS array is LENGTH / 2 - 1
> elements long (OFFSETS include gap before the first variable as well
> - as gaps after each stack variable). */
> + as gaps after each stack variable). PBASE is, if non-NULL, some pseudo
> + register which stack vars DECL_RTLs are based on. Either BASE should be
> + assigned to PBASE, when not doing use after return protection, or
> + corresponding address based on __asan_stack_malloc* return value. */
>
> rtx
> -asan_emit_stack_protection (rtx base, HOST_WIDE_INT *offsets, tree *decls,
> - int length)
> +asan_emit_stack_protection (rtx base, rtx pbase, HOST_WIDE_INT *offsets,
> + tree *decls, int length)
> {
> - rtx shadow_base, shadow_mem, ret, mem;
> + rtx shadow_base, shadow_mem, ret, mem, orig_base, lab;
> char buf[30];
> unsigned char shadow_bytes[4];
> HOST_WIDE_INT base_offset = offsets[length - 1], offset, prev_offset;
> + HOST_WIDE_INT asan_frame_size = offsets[0] - base_offset;
> HOST_WIDE_INT last_offset, last_size;
> int l;
> unsigned char cur_shadow_byte = ASAN_STACK_MAGIC_LEFT;
> tree str_cst, decl, id;
> + int use_after_return_class = -1;
>
> if (shadow_ptr_types[0] == NULL_TREE)
> asan_init_shadow_ptr_types ();
> @@ -982,9 +990,53 @@ asan_emit_stack_protection (rtx base, HO
> str_cst = asan_pp_string (&asan_pp);
>
> /* Emit the prologue sequence. */
> + if (asan_frame_size > 32 && asan_frame_size <= 65536 && pbase)
> + use_after_return_class = floor_log2 (asan_frame_size - 1) - 5;
> + if (use_after_return_class == -1 && pbase)
> + emit_move_insn (pbase, base);
> base = expand_binop (Pmode, add_optab, base,
> gen_int_mode (base_offset, Pmode),
> NULL_RTX, 1, OPTAB_DIRECT);
> + orig_base = NULL_RTX;
> + if (use_after_return_class != -1)
> + {
> + if (asan_detect_stack_use_after_return == NULL_TREE)
> + {
> + id = get_identifier ("__asan_option_detect_stack_use_after_return");
> + decl = build_decl (BUILTINS_LOCATION, VAR_DECL, id,
> + integer_type_node);
> + SET_DECL_ASSEMBLER_NAME (decl, id);
> + TREE_ADDRESSABLE (decl) = 1;
> + DECL_ARTIFICIAL (decl) = 1;
> + DECL_IGNORED_P (decl) = 1;
> + DECL_EXTERNAL (decl) = 1;
> + TREE_STATIC (decl) = 1;
> + TREE_PUBLIC (decl) = 1;
> + TREE_USED (decl) = 1;
> + asan_detect_stack_use_after_return = decl;
> + }
> + orig_base = gen_reg_rtx (Pmode);
> + emit_move_insn (orig_base, base);
> + ret = expand_normal (asan_detect_stack_use_after_return);
> + lab = gen_label_rtx ();
> + int very_likely = REG_BR_PROB_BASE - (REG_BR_PROB_BASE / 2000 - 1);
> + emit_cmp_and_jump_insns (ret, const0_rtx, EQ, NULL_RTX,
> + VOIDmode, 0, lab, very_likely);
> + snprintf (buf, sizeof buf, "__asan_stack_malloc_%d",
> + use_after_return_class);
> + ret = init_one_libfunc (buf);
> + rtx addr = convert_memory_address (ptr_mode, base);
> + ret = emit_library_call_value (ret, NULL_RTX, LCT_NORMAL, ptr_mode, 2,
> + GEN_INT (asan_frame_size),
> + TYPE_MODE (pointer_sized_int_node),
> + addr, ptr_mode);
> + ret = convert_memory_address (Pmode, ret);
> + emit_move_insn (base, ret);
> + emit_label (lab);
> + emit_move_insn (pbase, expand_binop (Pmode, add_optab, base,
> + gen_int_mode (-base_offset, Pmode),
> + NULL_RTX, 1, OPTAB_DIRECT));
> + }
> mem = gen_rtx_MEM (ptr_mode, base);
> emit_move_insn (mem, gen_int_mode (ASAN_STACK_FRAME_MAGIC, ptr_mode));
> mem = adjust_address (mem, VOIDmode, GET_MODE_SIZE (ptr_mode));
> @@ -1006,10 +1058,8 @@ asan_emit_stack_protection (rtx base, HO
> shadow_base = expand_binop (Pmode, lshr_optab, base,
> GEN_INT (ASAN_SHADOW_SHIFT),
> NULL_RTX, 1, OPTAB_DIRECT);
> - shadow_base = expand_binop (Pmode, add_optab, shadow_base,
> - gen_int_mode (targetm.asan_shadow_offset (),
> - Pmode),
> - NULL_RTX, 1, OPTAB_DIRECT);
> + shadow_base
> + = plus_constant (Pmode, shadow_base, targetm.asan_shadow_offset ());
> gcc_assert (asan_shadow_set != -1
> && (ASAN_RED_ZONE_SIZE >> ASAN_SHADOW_SHIFT) == 4);
> shadow_mem = gen_rtx_MEM (SImode, shadow_base);
> @@ -1060,6 +1110,47 @@ asan_emit_stack_protection (rtx base, HO
> /* Construct epilogue sequence. */
> start_sequence ();
>
> + lab = NULL_RTX;
> + if (use_after_return_class != -1)
> + {
> + rtx lab2 = gen_label_rtx ();
> + char c = (char) ASAN_STACK_MAGIC_USE_AFTER_RET;
> + int very_likely = REG_BR_PROB_BASE - (REG_BR_PROB_BASE / 2000 - 1);
> + emit_cmp_and_jump_insns (orig_base, base, EQ, NULL_RTX,
> + VOIDmode, 0, lab2, very_likely);
> + shadow_mem = gen_rtx_MEM (BLKmode, shadow_base);
> + set_mem_alias_set (shadow_mem, asan_shadow_set);
> + mem = gen_rtx_MEM (ptr_mode, base);
> + emit_move_insn (mem, gen_int_mode (ASAN_STACK_RETIRED_MAGIC, ptr_mode));
> + if (use_after_return_class < 5
> + && can_store_by_pieces (asan_frame_size >> ASAN_SHADOW_SHIFT,
> + builtin_memset_read_str, &c, BITS_PER_UNIT,
> + true))
> + store_by_pieces (shadow_mem, asan_frame_size >> ASAN_SHADOW_SHIFT,
> + builtin_memset_read_str, &c, BITS_PER_UNIT, true, 0);
> + else if (use_after_return_class >= 5
> + || !set_storage_via_setmem (shadow_mem,
> + GEN_INT (asan_frame_size
> + >> ASAN_SHADOW_SHIFT),
> + gen_int_mode (c, QImode),
> + BITS_PER_UNIT, BITS_PER_UNIT,
> + -1))
> + {
> + snprintf (buf, sizeof buf, "__asan_stack_free_%d",
> + use_after_return_class);
> + ret = init_one_libfunc (buf);
> + rtx addr = convert_memory_address (ptr_mode, base);
> + rtx orig_addr = convert_memory_address (ptr_mode, orig_base);
> + emit_library_call (ret, LCT_NORMAL, ptr_mode, 3, addr, ptr_mode,
> + GEN_INT (asan_frame_size),
> + TYPE_MODE (pointer_sized_int_node),
> + orig_addr, ptr_mode);
> + }
> + lab = gen_label_rtx ();
> + emit_jump (lab);
> + emit_label (lab2);
> + }
> +
> shadow_mem = gen_rtx_MEM (BLKmode, shadow_base);
> set_mem_alias_set (shadow_mem, asan_shadow_set);
> prev_offset = base_offset;
> @@ -1092,6 +1183,8 @@ asan_emit_stack_protection (rtx base, HO
> }
>
> do_pending_stack_adjust ();
> + if (lab)
> + emit_label (lab);
>
> ret = get_insns ();
> end_sequence ();
> --- gcc/asan.h.jj 2013-11-12 11:31:23.000000000 +0100
> +++ gcc/asan.h 2013-11-14 15:42:57.371998293 +0100
> @@ -23,7 +23,7 @@ along with GCC; see the file COPYING3.
>
> extern void asan_function_start (void);
> extern void asan_finish_file (void);
> -extern rtx asan_emit_stack_protection (rtx, HOST_WIDE_INT *, tree *, int);
> +extern rtx asan_emit_stack_protection (rtx, rtx, HOST_WIDE_INT *, tree *, int);
> extern bool asan_protect_global (tree);
> extern void initialize_sanitizer_builtins (void);
>
> @@ -48,8 +48,10 @@ extern alias_set_type asan_shadow_set;
> #define ASAN_STACK_MAGIC_MIDDLE 0xf2
> #define ASAN_STACK_MAGIC_RIGHT 0xf3
> #define ASAN_STACK_MAGIC_PARTIAL 0xf4
> +#define ASAN_STACK_MAGIC_USE_AFTER_RET 0xf5
>
> -#define ASAN_STACK_FRAME_MAGIC 0x41b58ab3
> +#define ASAN_STACK_FRAME_MAGIC 0x41b58ab3
> +#define ASAN_STACK_RETIRED_MAGIC 0x45e0360e
>
> /* Return true if DECL should be guarded on the stack. */
>
>
>
> Jakub