On Wed, Dec 5, 2012 at 3:39 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> Another problem from the compiler side when working on the asan testsuite
> is that at higher -O* levels the __asan_report_* noreturn calls are
> cross-jumped, but the library relies on their locus to print accurrate
> locations when symbolized. Without it, asan might report an error
> completely elsewhere in a function.
In LLVM we solve this problem by inserting an empty volatile asm blob
after the __asan_report_* calls.
Hacky, but works remarkably well.
--kcc
>
> This patch disables cross-jumping of such builtins.
> Alternatively, I could introduce some attribute (no_cross_jump?),
> ECF_NO_CROSS_JUMP, add those attributes to those builtins (and let users
> add those too to functions they wish), and look at ECF_NO_CROSS_JUMP instead
> during cross-jumping.
>
> 2012-12-05 Jakub Jelinek <ja...@redhat.com>
>
> * sanitizer.def: Add comment about importance of ordering of
> BUILT_IN_ASAN_REPORT* builtins.
> * cfgcleanup.c (old_insns_match_p): Don't cross-jump __asan_report_*
> builtins.
>
> --- gcc/sanitizer.def.jj 2012-12-04 14:19:36.000000000 +0100
> +++ gcc/sanitizer.def 2012-12-05 09:38:01.205958515 +0100
> @@ -29,6 +29,8 @@ along with GCC; see the file COPYING3.
> /* Address Sanitizer */
> DEF_SANITIZER_BUILTIN(BUILT_IN_ASAN_INIT, "__asan_init",
> BT_FN_VOID, ATTR_NOTHROW_LEAF_LIST)
> +/* Do not reorder the BUILT_IN_ASAN_REPORT* builtins, e.g. cfgcleanup.c
> + relies on this order. */
> DEF_SANITIZER_BUILTIN(BUILT_IN_ASAN_REPORT_LOAD1, "__asan_report_load1",
> BT_FN_VOID_PTR, ATTR_NORETURN_NOTHROW_LEAF_LIST)
> DEF_SANITIZER_BUILTIN(BUILT_IN_ASAN_REPORT_LOAD2, "__asan_report_load2",
> --- gcc/cfgcleanup.c.jj 2012-11-20 09:37:47.000000000 +0100
> +++ gcc/cfgcleanup.c 2012-12-05 09:37:23.389181984 +0100
> @@ -1138,6 +1138,28 @@ old_insns_match_p (int mode ATTRIBUTE_UN
> CALL_INSN_FUNCTION_USAGE (i2))
> || SIBLING_CALL_P (i1) != SIBLING_CALL_P (i2))
> return dir_none;
> +
> + /* For address sanitizer, never crossjump __asan_report_* builtins,
> + otherwise errors might be reported on incorrect lines. */
> + if (flag_asan)
> + {
> + rtx call = get_call_rtx_from (i1);
> + if (call && GET_CODE (XEXP (XEXP (call, 0), 0)) == SYMBOL_REF)
> + {
> + rtx symbol = XEXP (XEXP (call, 0), 0);
> + if (SYMBOL_REF_DECL (symbol)
> + && TREE_CODE (SYMBOL_REF_DECL (symbol)) == FUNCTION_DECL)
> + {
> + if ((DECL_BUILT_IN_CLASS (SYMBOL_REF_DECL (symbol))
> + == BUILT_IN_NORMAL)
> + && DECL_FUNCTION_CODE (SYMBOL_REF_DECL (symbol))
> + >= BUILT_IN_ASAN_REPORT_LOAD1
> + && DECL_FUNCTION_CODE (SYMBOL_REF_DECL (symbol))
> + <= BUILT_IN_ASAN_REPORT_STORE16)
> + return dir_none;
> + }
> + }
> + }
> }
>
> #ifdef STACK_REGS
>
> Jakub
