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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86: miscellaneous emulator adjustments
How did you test this patch ?
Christoph
On Tuesday 18 August 2009 15:18:49 Jan Beulich wrote:
> Defer fail_if()-s as much as possible (in favor of possibly generating
> exceptions), and avoid generating exceptions when not strictly
> necessary.
>
> Avoid fail_if()-s for simple return code checks (making the code that
> used them consistent with other, longer existing code).
>
> Eliminate redundant generate_exception_if()-s checking lock_prefix
> (which is already covered by the general check prior to decoding
> operands).
>
> Also fix the testing code to add PROT_EXEC for the mapping that is
> intended to have instruction executed from.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>
> --- 2009-08-18.orig/tools/tests/test_x86_emulator.c 2008-07-18
> 16:19:34.000000000 +0200 +++
> 2009-08-18/tools/tests/test_x86_emulator.c 2009-08-18 14:18:20.000000000
> +0200 @@ -76,7 +76,7 @@ int main(int argc, char **argv)
> ctxt.addr_size = 32;
> ctxt.sp_size = 32;
>
> - res = mmap((void *)0x100000, MMAP_SZ, PROT_READ|PROT_WRITE,
> + res = mmap((void *)0x100000, MMAP_SZ, PROT_READ|PROT_WRITE|PROT_EXEC,
> MAP_FIXED|MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
> if ( res == MAP_FAILED )
> {
> --- 2009-08-18.orig/xen/arch/x86/x86_emulate/x86_emulate.c 2009-08-18
> 14:18:15.000000000 +0200 +++
> 2009-08-18/xen/arch/x86/x86_emulate/x86_emulate.c 2009-08-18
> 14:18:20.000000000 +0200 @@ -3583,21 +3583,17 @@ x86_emulate(
> struct segment_register cs = { 0 }, ss = { 0 };
> int rc;
>
> - fail_if(ops->read_msr == NULL);
> - fail_if(ops->read_segment == NULL);
> - fail_if(ops->write_segment == NULL);
> -
> generate_exception_if(in_realmode(ctxt, ops), EXC_UD, 0);
> generate_exception_if(!in_protmode(ctxt, ops), EXC_UD, 0);
> - generate_exception_if(lock_prefix, EXC_UD, 0);
>
> /* Inject #UD if syscall/sysret are disabled. */
> - rc = ops->read_msr(MSR_EFER, &msr_content, ctxt);
> - fail_if(rc != 0);
> + fail_if(ops->read_msr == NULL);
> + if ( (rc = ops->read_msr(MSR_EFER, &msr_content, ctxt)) != 0 )
> + goto done;
> generate_exception_if((msr_content & EFER_SCE) == 0, EXC_UD, 0);
>
> - rc = ops->read_msr(MSR_STAR, &msr_content, ctxt);
> - fail_if(rc != 0);
> + if ( (rc = ops->read_msr(MSR_STAR, &msr_content, ctxt)) != 0 )
> + goto done;
>
> msr_content >>= 32;
> cs.sel = (uint16_t)(msr_content & 0xfffc);
> @@ -3617,27 +3613,27 @@ x86_emulate(
> _regs.rcx = _regs.rip;
> _regs.r11 = _regs.eflags & ~EFLG_RF;
>
> - rc = ops->read_msr(mode_64bit() ? MSR_LSTAR : MSR_CSTAR,
> - &msr_content, ctxt);
> - fail_if(rc != 0);
> -
> + if ( (rc = ops->read_msr(mode_64bit() ? MSR_LSTAR : MSR_CSTAR,
> + &msr_content, ctxt)) != 0 )
> + goto done;
> _regs.rip = msr_content;
>
> - rc = ops->read_msr(MSR_FMASK, &msr_content, ctxt);
> - fail_if(rc != 0);
> + if ( (rc = ops->read_msr(MSR_FMASK, &msr_content, ctxt)) != 0
> ) + goto done;
> _regs.eflags &= ~(msr_content | EFLG_RF);
> }
> else
> #endif
> {
> - rc = ops->read_msr(MSR_STAR, &msr_content, ctxt);
> - fail_if(rc != 0);
> + if ( (rc = ops->read_msr(MSR_STAR, &msr_content, ctxt)) != 0 )
> + goto done;
>
> _regs.ecx = _regs.eip;
> _regs.eip = (uint32_t)msr_content;
> _regs.eflags &= ~(EFLG_VM | EFLG_IF | EFLG_RF);
> }
>
> + fail_if(ops->write_segment == NULL);
> if ( (rc = ops->write_segment(x86_seg_cs, &cs, ctxt)) ||
> (rc = ops->write_segment(x86_seg_ss, &ss, ctxt)) )
> goto done;
> @@ -3717,10 +3713,13 @@ x86_emulate(
> case 0x31: /* rdtsc */ {
> unsigned long cr4;
> uint64_t val;
> - fail_if(ops->read_cr == NULL);
> - if ( (rc = ops->read_cr(4, &cr4, ctxt)) )
> - goto done;
> - generate_exception_if((cr4 & CR4_TSD) && !mode_ring0(), EXC_GP,
> 0); + if ( !mode_ring0() )
> + {
> + fail_if(ops->read_cr == NULL);
> + if ( (rc = ops->read_cr(4, &cr4, ctxt)) )
> + goto done;
> + generate_exception_if(cr4 & CR4_TSD, EXC_GP, 0);
> + }
> fail_if(ops->read_msr == NULL);
> if ( (rc = ops->read_msr(MSR_TSC, &val, ctxt)) != 0 )
> goto done;
> @@ -3751,17 +3750,13 @@ x86_emulate(
> struct segment_register cs, ss;
> int rc;
>
> - fail_if(ops->read_msr == NULL);
> - fail_if(ops->read_segment == NULL);
> - fail_if(ops->write_segment == NULL);
> -
> generate_exception_if(mode_ring0(), EXC_GP, 0);
> generate_exception_if(in_realmode(ctxt, ops), EXC_GP, 0);
> generate_exception_if(!in_protmode(ctxt, ops), EXC_GP, 0);
> - generate_exception_if(lock_prefix, EXC_UD, 0);
>
> - rc = ops->read_msr(MSR_SYSENTER_CS, &msr_content, ctxt);
> - fail_if(rc != 0);
> + fail_if(ops->read_msr == NULL);
> + if ( (rc = ops->read_msr(MSR_SYSENTER_CS, &msr_content, ctxt)) !=
> 0 ) + goto done;
>
> if ( mode_64bit() )
> generate_exception_if(msr_content == 0, EXC_GP, 0);
> @@ -3770,6 +3765,7 @@ x86_emulate(
>
> _regs.eflags &= ~(EFLG_VM | EFLG_IF | EFLG_RF);
>
> + fail_if(ops->read_segment == NULL);
> ops->read_segment(x86_seg_cs, &cs, ctxt);
> cs.sel = (uint16_t)msr_content & ~3; /* SELECTOR_RPL_MASK */
> cs.base = 0; /* flat segment */
> @@ -3787,17 +3783,17 @@ x86_emulate(
> cs.attr.fields.l = 1;
> }
>
> - rc = ops->write_segment(x86_seg_cs, &cs, ctxt);
> - fail_if(rc != 0);
> - rc = ops->write_segment(x86_seg_ss, &ss, ctxt);
> - fail_if(rc != 0);
> + fail_if(ops->write_segment == NULL);
> + if ( (rc = ops->write_segment(x86_seg_cs, &cs, ctxt)) != 0 ||
> + (rc = ops->write_segment(x86_seg_ss, &ss, ctxt)) != 0 )
> + goto done;
>
> - rc = ops->read_msr(MSR_SYSENTER_EIP, &msr_content, ctxt);
> - fail_if(rc != 0);
> + if ( (rc = ops->read_msr(MSR_SYSENTER_EIP, &msr_content, ctxt)) !=
> 0 ) + goto done;
> _regs.eip = msr_content;
>
> - rc = ops->read_msr(MSR_SYSENTER_ESP, &msr_content, ctxt);
> - fail_if(rc != 0);
> + if ( (rc = ops->read_msr(MSR_SYSENTER_ESP, &msr_content, ctxt)) !=
> 0 ) + goto done;
> _regs.esp = msr_content;
>
> break;
> @@ -3809,19 +3805,13 @@ x86_emulate(
> int user64 = !!(rex_prefix & 8); /* REX.W */
> int rc;
>
> - fail_if(ops->read_msr == NULL);
> - fail_if(ops->read_segment == NULL);
> - fail_if(ops->write_segment == NULL);
> -
> generate_exception_if(!mode_ring0(), EXC_GP, 0);
> generate_exception_if(in_realmode(ctxt, ops), EXC_GP, 0);
> generate_exception_if(!in_protmode(ctxt, ops), EXC_GP, 0);
> - generate_exception_if(lock_prefix, EXC_UD, 0);
>
> - rc = ops->read_msr(MSR_SYSENTER_CS, &msr_content, ctxt);
> - fail_if(rc != 0);
> - rc = ops->read_segment(x86_seg_cs, &cs, ctxt);
> - fail_if(rc != 0);
> + fail_if(ops->read_msr == NULL);
> + if ( (rc = ops->read_msr(MSR_SYSENTER_CS, &msr_content, ctxt)) !=
> 0 ) + goto done;
>
> if ( user64 )
> {
> @@ -3852,10 +3842,10 @@ x86_emulate(
> cs.attr.fields.l = 1;
> }
>
> - rc = ops->write_segment(x86_seg_cs, &cs, ctxt);
> - fail_if(rc != 0);
> - rc = ops->write_segment(x86_seg_ss, &ss, ctxt);
> - fail_if(rc != 0);
> + fail_if(ops->write_segment == NULL);
> + if ( (rc = ops->write_segment(x86_seg_cs, &cs, ctxt)) != 0 ||
> + (rc = ops->write_segment(x86_seg_ss, &ss, ctxt)) != 0 )
> + goto done;
>
> _regs.eip = _regs.edx;
> _regs.esp = _regs.ecx;
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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