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;
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