On Tuesday 18 August 2009 16:55:04 Jan Beulich wrote:
> I didn't do significantly more testing than what the test utility does plus
> bring up a couple of HVM guests.
>
> Do you see anything obviously wrong with it (after all, it's mainly code
> re-ordering)?
No, I don't. I just ask, because the syscall/sysret emulation path is not that
easy to test like you did.
Christoph
>
> Jan
>
> >>> Christoph Egger <Christoph.Egger@xxxxxxx> 18.08.09 16:12 >>>
>
> 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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