Re: [Xen-devel] [PATCH] tools/tests: Add EIP check to test_x86_emulator.c

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/08/2014 09:16, Razvan Cojocaru wrote:
> The test now also checks that EIP was modified after emulating
> instructions after (and including) the "movq %mm3,(%ecx)..."
> code block.
>
> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

These checks do check that the instruction pointer has changed, which
catches your problem, but doesn't check that it has changed correctly. 
You need to work out exactly how long the instruction is a verify that
eip points to first byte of the next instruction.

~Andrew

> ---
>  tools/tests/x86_emulator/test_x86_emulator.c |   30 
> +++++++++++++++++---------
>  1 file changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/tools/tests/x86_emulator/test_x86_emulator.c 
> b/tools/tests/x86_emulator/test_x86_emulator.c
> index 0a00d5a..dd4e986 100644
> --- a/tools/tests/x86_emulator/test_x86_emulator.c
> +++ b/tools/tests/x86_emulator/test_x86_emulator.c
> @@ -615,7 +615,8 @@ int main(int argc, char **argv)
>          regs.eip    = (unsigned long)&instr[0];
>          regs.ecx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) )
> +        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          printf("okay\n");
>      }
> @@ -637,7 +638,8 @@ int main(int argc, char **argv)
>          regs.ecx    = 0;
>          regs.edx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( rc != X86EMUL_OKAY )
> +        if ( rc != X86EMUL_OKAY ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          asm ( "pcmpeqb %%mm3, %%mm3\n\t"
>                "pcmpeqb %%mm5, %%mm3\n\t"
> @@ -665,7 +667,8 @@ int main(int argc, char **argv)
>          regs.eip    = (unsigned long)&instr[0];
>          regs.ecx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) )
> +        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          printf("okay\n");
>      }
> @@ -687,7 +690,8 @@ int main(int argc, char **argv)
>          regs.ecx    = 0;
>          regs.edx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( rc != X86EMUL_OKAY )
> +        if ( rc != X86EMUL_OKAY ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          asm ( "pcmpeqb %%xmm2, %%xmm2\n\t"
>                "pcmpeqb %%xmm4, %%xmm2\n\t"
> @@ -716,7 +720,8 @@ int main(int argc, char **argv)
>          regs.eip    = (unsigned long)&instr[0];
>          regs.ecx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 16, 64) )
> +        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 16, 64) ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          printf("okay\n");
>      }
> @@ -744,7 +749,8 @@ int main(int argc, char **argv)
>          regs.ecx    = 0;
>          regs.edx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( rc != X86EMUL_OKAY )
> +        if ( rc != X86EMUL_OKAY ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>  #if 0 /* Don't use AVX2 instructions for now */
>          asm ( "vpcmpeqb %%ymm2, %%ymm2, %%ymm2\n\t"
> @@ -784,7 +790,8 @@ int main(int argc, char **argv)
>          regs.ecx    = (unsigned long)(res + 2);
>          regs.edx    = 0;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) )
> +        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          printf("okay\n");
>      }
> @@ -809,7 +816,8 @@ int main(int argc, char **argv)
>          regs.ecx    = 0;
>          regs.edx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( rc != X86EMUL_OKAY )
> +        if ( rc != X86EMUL_OKAY ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          asm ( "cmpeqps %1, %%xmm7\n\t"
>                "movmskps %%xmm7, %0" : "=r" (rc) : "m" (res[8]) );
> @@ -837,7 +845,8 @@ int main(int argc, char **argv)
>          regs.ecx    = (unsigned long)(res + 2);
>          regs.edx    = 0;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) )
> +        if ( (rc != X86EMUL_OKAY) || memcmp(res, res + 8, 32) ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          printf("okay\n");
>      }
> @@ -862,7 +871,8 @@ int main(int argc, char **argv)
>          regs.ecx    = 0;
>          regs.edx    = (unsigned long)res;
>          rc = x86_emulate(&ctxt, &emulops);
> -        if ( rc != X86EMUL_OKAY )
> +        if ( rc != X86EMUL_OKAY ||
> +             (regs.eip == (unsigned long)&instr[0]) )
>              goto fail;
>          asm ( "vcmpeqps %1, %%ymm7, %%ymm0\n\t"
>                "vmovmskps %%ymm0, %0" : "=r" (rc) : "m" (res[8]) );


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