[llvm-commits] [compiler-rt] r153249 - /compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c

[Kostya Serebryany]

the same general comments as before:
1. we need to notify the mach_override authors/maintainers
2. I'd like to get rid of mach_override completely. Any MacOS expert's
advice is welcome!

--kcc

On Thu, Mar 22, 2012 at 4:29 AM, Alexander Potapenko <glider at google.com>wrote:

> Author: glider
> Date: Thu Mar 22 06:29:53 2012
> New Revision: 153249
>
> URL: http://llvm.org/viewvc/llvm-project?rev=153249&view=rev
> Log:
> Handle two-byte short jumps in the relocated code.
> After the instructions are moved to the branch island, fixupInstructions()
> expands every 2-byte ja/je instruction with a 1-byte offset into a 6-byte
> ja/je with 32-bit offset. The offset is fixed to point to the original
> function.
>
>
> Modified:
>    compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c
>
> Modified:
> compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c?rev=153249&r1=153248&r2=153249&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c
> (original)
> +++ compiler-rt/trunk/lib/asan/interception/mach_override/mach_override.c
> Thu Mar 22 06:29:53 2012
> @@ -157,6 +157,12 @@
>     void               *instructionsToFix,
>        int                     instructionCount,
>        uint8_t         *instructionSizes )
> __attribute__((visibility("hidden")));
> +
> +#ifdef DEBUG_DISASM
> +       static void
> +dump16Bytes(
> +       void    *ptr);
> +#endif  // DEBUG_DISASM
>  #endif
>
>
>  /*******************************************************************************
> @@ -830,9 +836,21 @@
>        int                     instructionCount,
>        uint8_t         *instructionSizes )
>  {
> -       int     index;
> +       void *initialOriginalFunction = originalFunction;
> +       int     index, fixed_size, code_size = 0;
> +       for (index = 0;index < instructionCount;index += 1)
> +               code_size += instructionSizes[index];
> +
> +#ifdef DEBUG_DISASM
> +       void *initialInstructionsToFix = instructionsToFix;
> +       fprintf(stderr, "BEFORE FIXING:\n");
> +       dump16Bytes(initialOriginalFunction);
> +       dump16Bytes(initialInstructionsToFix);
> +#endif  // DEBUG_DISASM
> +
>        for (index = 0;index < instructionCount;index += 1)
>        {
> +                fixed_size = instructionSizes[index];
>                if ((*(uint8_t*)instructionsToFix == 0xE9) || // 32-bit
> jump relative
>                    (*(uint8_t*)instructionsToFix == 0xE8))   // 32-bit
> call relative
>                {
> @@ -840,13 +858,56 @@
>                        uint32_t *jumpOffsetPtr =
> (uint32_t*)((uintptr_t)instructionsToFix + 1);
>                        *jumpOffsetPtr += offset;
>                }
> -
> +               if ((*(uint8_t*)instructionsToFix == 0x74) ||  // Near
> jump if equal (je), 2 bytes.
> +                   (*(uint8_t*)instructionsToFix == 0x77))    // Near
> jump if above (ja), 2 bytes.
> +               {
> +                       // We replace a near je/ja instruction, "7P JJ",
> with a 32-bit je/ja, "0F 8P WW XX YY ZZ".
> +                       // This is critical, otherwise a near jump will
> likely fall outside the original function.
> +                       uint32_t offset =
> (uintptr_t)initialOriginalFunction - (uintptr_t)escapeIsland;
> +                       uint32_t jumpOffset =
> *(uint8_t*)((uintptr_t)instructionsToFix + 1);
> +                       *(uint8_t*)(instructionsToFix + 1) =
> *(uint8_t*)instructionsToFix + 0x10;
> +                       *(uint8_t*)instructionsToFix = 0x0F;
> +                       uint32_t *jumpOffsetPtr =
> (uint32_t*)((uintptr_t)instructionsToFix + 2 );
> +                       *jumpOffsetPtr = offset + jumpOffset;
> +                       fixed_size = 6;
> +                }
>
>                originalFunction = (void*)((uintptr_t)originalFunction +
> instructionSizes[index]);
>                escapeIsland = (void*)((uintptr_t)escapeIsland +
> instructionSizes[index]);
> -               instructionsToFix = (void*)((uintptr_t)instructionsToFix +
> instructionSizes[index]);
> -    }
> +               instructionsToFix = (void*)((uintptr_t)instructionsToFix +
> fixed_size);
> +
> +               // Expanding short instructions into longer ones may
> overwrite the next instructions,
> +               // so we must restore them.
> +               code_size -= fixed_size;
> +               if ((code_size > 0) && (fixed_size !=
> instructionSizes[index])) {
> +                       bcopy(originalFunction, instructionsToFix,
> code_size);
> +               }
> +       }
> +#ifdef DEBUG_DISASM
> +       fprintf(stderr, "AFTER_FIXING:\n");
> +       dump16Bytes(initialOriginalFunction);
> +       dump16Bytes(initialInstructionsToFix);
> +#endif  // DEBUG_DISASM
> +}
> +
> +#ifdef DEBUG_DISASM
> +#define HEX_DIGIT(x) ((((x) % 16) < 10) ? ('0' + ((x) % 16)) : ('A' +
> ((x) % 16 - 10)))
> +
> +       static void
> +dump16Bytes(
> +       void    *ptr) {
> +       int i;
> +       char buf[3];
> +       uint8_t *bytes = (uint8_t*)ptr;
> +       for (i = 0; i < 16; i++) {
> +               buf[0] = HEX_DIGIT(bytes[i] / 16);
> +               buf[1] = HEX_DIGIT(bytes[i] % 16);
> +               buf[2] = ' ';
> +               write(2, buf, 3);
> +       }
> +       write(2, "\n", 1);
>  }
> +#endif  // DEBUG_DISASM
>  #endif
>
>  #if defined(__i386__)
>
>
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