From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Petre Pircalabu <ppircalabu@bitdefender.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: [PATCH RFC] x86/emul: Fix the handling of unimplemented Grp7 instructions
Date: Mon, 4 Sep 2017 18:21:01 +0100 [thread overview]
Message-ID: <1504545661-24626-1-git-send-email-andrew.cooper3@citrix.com> (raw)
Grp7 is abnormally complicated to decode, even by x86's standards, with
{s,l}msw being the problematic cases.
Previously, any value which fell through the first switch statement (looking
for instructions with entirely implicit operands) would be interpreted by the
second switch statement (handling instructions with memory operands).
Unimplemented instructions would then hit the #UD case for having a non-memory
operand, rather than taking the cannot_emulate path.
Place a big if/else around the two switch statements (accounting for {s,l}msw
which need handling in the else clause), so both switch statments can have a
default goto cannot_emulate path.
Reported-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Petre Pircalabu <ppircalabu@bitdefender.com>
RFC as I've only done light testing so far.
---
xen/arch/x86/x86_emulate/x86_emulate.c | 353 +++++++++++++++++----------------
1 file changed, 184 insertions(+), 169 deletions(-)
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index 2201852..af3d8da 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4987,197 +4987,212 @@ x86_emulate(
}
break;
- case X86EMUL_OPC(0x0f, 0x01): /* Grp7 */ {
- unsigned long base, limit, cr0, cr0w;
+ case X86EMUL_OPC(0x0f, 0x01): /* Grp7 */
+ {
+ unsigned long base, limit;
- switch( modrm )
+ if ( (modrm & 0xc0) == 0xc0 &&
+ (modrm_reg & 7) != 4 /* smsw */ &&
+ (modrm_reg & 7) != 6 /* lmsw */ )
{
- case 0xca: /* clac */
- case 0xcb: /* stac */
- vcpu_must_have(smap);
- generate_exception_if(vex.pfx || !mode_ring0(), EXC_UD);
-
- _regs.eflags &= ~X86_EFLAGS_AC;
- if ( modrm == 0xcb )
- _regs.eflags |= X86_EFLAGS_AC;
- goto complete_insn;
+ switch ( modrm )
+ {
+ case 0xca: /* clac */
+ case 0xcb: /* stac */
+ vcpu_must_have(smap);
+ generate_exception_if(vex.pfx || !mode_ring0(), EXC_UD);
+
+ _regs.eflags &= ~X86_EFLAGS_AC;
+ if ( modrm == 0xcb )
+ _regs.eflags |= X86_EFLAGS_AC;
+ goto complete_insn;
#ifdef __XEN__
- case 0xd1: /* xsetbv */
- generate_exception_if(vex.pfx, EXC_UD);
- if ( !ops->read_cr || ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY )
- cr4 = 0;
- generate_exception_if(!(cr4 & X86_CR4_OSXSAVE), EXC_UD);
- generate_exception_if(!mode_ring0() ||
- handle_xsetbv(_regs.ecx,
- _regs.eax | (_regs.rdx << 32)),
- EXC_GP, 0);
- goto complete_insn;
+ case 0xd1: /* xsetbv */
+ generate_exception_if(vex.pfx, EXC_UD);
+ if ( !ops->read_cr ||
+ ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY )
+ cr4 = 0;
+ generate_exception_if(!(cr4 & X86_CR4_OSXSAVE), EXC_UD);
+ generate_exception_if(!mode_ring0() ||
+ handle_xsetbv(_regs.ecx, _regs.eax |
+ (_regs.rdx << 32)),
+ EXC_GP, 0);
+ goto complete_insn;
#endif
- case 0xd4: /* vmfunc */
- generate_exception_if(vex.pfx, EXC_UD);
- fail_if(!ops->vmfunc);
- if ( (rc = ops->vmfunc(ctxt)) != X86EMUL_OKAY )
- goto done;
- goto complete_insn;
-
- case 0xd5: /* xend */
- generate_exception_if(vex.pfx, EXC_UD);
- generate_exception_if(!vcpu_has_rtm(), EXC_UD);
- generate_exception_if(vcpu_has_rtm(), EXC_GP, 0);
- break;
-
- case 0xd6: /* xtest */
- generate_exception_if(vex.pfx, EXC_UD);
- generate_exception_if(!vcpu_has_rtm() && !vcpu_has_hle(),
- EXC_UD);
- /* Neither HLE nor RTM can be active when we get here. */
- _regs.eflags |= X86_EFLAGS_ZF;
- goto complete_insn;
+ case 0xd4: /* vmfunc */
+ generate_exception_if(vex.pfx, EXC_UD);
+ fail_if(!ops->vmfunc);
+ if ( (rc = ops->vmfunc(ctxt)) != X86EMUL_OKAY )
+ goto done;
+ goto complete_insn;
- case 0xdf: /* invlpga */
- generate_exception_if(!in_protmode(ctxt, ops), EXC_UD);
- generate_exception_if(!mode_ring0(), EXC_GP, 0);
- fail_if(ops->invlpg == NULL);
- if ( (rc = ops->invlpg(x86_seg_none, truncate_ea(_regs.r(ax)),
- ctxt)) )
- goto done;
- goto complete_insn;
+ case 0xd5: /* xend */
+ generate_exception_if(vex.pfx, EXC_UD);
+ generate_exception_if(!vcpu_has_rtm(), EXC_UD);
+ generate_exception_if(vcpu_has_rtm(), EXC_GP, 0);
+ break;
- case 0xf9: /* rdtscp */
- fail_if(ops->read_msr == NULL);
- if ( (rc = ops->read_msr(MSR_TSC_AUX,
- &msr_val, ctxt)) != X86EMUL_OKAY )
- goto done;
- _regs.r(cx) = (uint32_t)msr_val;
- goto rdtsc;
+ case 0xd6: /* xtest */
+ generate_exception_if(vex.pfx, EXC_UD);
+ generate_exception_if(!vcpu_has_rtm() && !vcpu_has_hle(),
+ EXC_UD);
+ /* Neither HLE nor RTM can be active when we get here. */
+ _regs.eflags |= X86_EFLAGS_ZF;
+ goto complete_insn;
- case 0xfc: /* clzero */
- {
- unsigned long zero = 0;
+ case 0xdf: /* invlpga */
+ generate_exception_if(!in_protmode(ctxt, ops), EXC_UD);
+ generate_exception_if(!mode_ring0(), EXC_GP, 0);
+ fail_if(ops->invlpg == NULL);
+ if ( (rc = ops->invlpg(x86_seg_none, truncate_ea(_regs.r(ax)),
+ ctxt)) )
+ goto done;
+ goto complete_insn;
- vcpu_must_have(clzero);
+ case 0xf9: /* rdtscp */
+ fail_if(ops->read_msr == NULL);
+ if ( (rc = ops->read_msr(MSR_TSC_AUX,
+ &msr_val, ctxt)) != X86EMUL_OKAY )
+ goto done;
+ _regs.r(cx) = (uint32_t)msr_val;
+ goto rdtsc;
- base = ad_bytes == 8 ? _regs.r(ax) :
- ad_bytes == 4 ? _regs.eax : _regs.ax;
- limit = 0;
- if ( vcpu_has_clflush() &&
- ops->cpuid(1, 0, &cpuid_leaf, ctxt) == X86EMUL_OKAY )
- limit = ((cpuid_leaf.b >> 8) & 0xff) * 8;
- generate_exception_if(limit < sizeof(long) ||
- (limit & (limit - 1)), EXC_UD);
- base &= ~(limit - 1);
- if ( ops->rep_stos )
+ case 0xfc: /* clzero */
{
- unsigned long nr_reps = limit / sizeof(zero);
+ unsigned long zero = 0;
+
+ vcpu_must_have(clzero);
+
+ base = ad_bytes == 8 ? _regs.r(ax) :
+ ad_bytes == 4 ? _regs.eax : _regs.ax;
+ limit = 0;
+ if ( vcpu_has_clflush() &&
+ ops->cpuid(1, 0, &cpuid_leaf, ctxt) == X86EMUL_OKAY )
+ limit = ((cpuid_leaf.b >> 8) & 0xff) * 8;
+ generate_exception_if(limit < sizeof(long) ||
+ (limit & (limit - 1)), EXC_UD);
+ base &= ~(limit - 1);
+ if ( ops->rep_stos )
+ {
+ unsigned long nr_reps = limit / sizeof(zero);
- rc = ops->rep_stos(&zero, ea.mem.seg, base, sizeof(zero),
- &nr_reps, ctxt);
- if ( rc == X86EMUL_OKAY )
+ rc = ops->rep_stos(&zero, ea.mem.seg, base, sizeof(zero),
+ &nr_reps, ctxt);
+ if ( rc == X86EMUL_OKAY )
+ {
+ base += nr_reps * sizeof(zero);
+ limit -= nr_reps * sizeof(zero);
+ }
+ else if ( rc != X86EMUL_UNHANDLEABLE )
+ goto done;
+ }
+ fail_if(limit && !ops->write);
+ while ( limit )
{
- base += nr_reps * sizeof(zero);
- limit -= nr_reps * sizeof(zero);
+ rc = ops->write(ea.mem.seg, base, &zero,
+ sizeof(zero), ctxt);
+ if ( rc != X86EMUL_OKAY )
+ goto done;
+ base += sizeof(zero);
+ limit -= sizeof(zero);
}
- else if ( rc != X86EMUL_UNHANDLEABLE )
- goto done;
+ goto complete_insn;
}
- fail_if(limit && !ops->write);
- while ( limit )
- {
- rc = ops->write(ea.mem.seg, base, &zero, sizeof(zero), ctxt);
- if ( rc != X86EMUL_OKAY )
- goto done;
- base += sizeof(zero);
- limit -= sizeof(zero);
+
+ default:
+ goto cannot_emulate;
}
- goto complete_insn;
- }
}
+ else
+ {
+ unsigned long cr0, cr0w;
- seg = (modrm_reg & 1) ? x86_seg_idtr : x86_seg_gdtr;
+ seg = (modrm_reg & 1) ? x86_seg_idtr : x86_seg_gdtr;
- switch ( modrm_reg & 7 )
- {
- case 0: /* sgdt */
- case 1: /* sidt */
- generate_exception_if(ea.type != OP_MEM, EXC_UD);
- generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
- fail_if(!ops->read_segment || !ops->write);
- if ( (rc = ops->read_segment(seg, &sreg, ctxt)) )
- goto done;
- if ( mode_64bit() )
- op_bytes = 8;
- else if ( op_bytes == 2 )
- {
- sreg.base &= 0xffffff;
- op_bytes = 4;
- }
- if ( (rc = ops->write(ea.mem.seg, ea.mem.off, &sreg.limit,
- 2, ctxt)) != X86EMUL_OKAY ||
- (rc = ops->write(ea.mem.seg, ea.mem.off + 2, &sreg.base,
- op_bytes, ctxt)) != X86EMUL_OKAY )
- goto done;
- break;
- case 2: /* lgdt */
- case 3: /* lidt */
- generate_exception_if(!mode_ring0(), EXC_GP, 0);
- generate_exception_if(ea.type != OP_MEM, EXC_UD);
- fail_if(ops->write_segment == NULL);
- memset(&sreg, 0, sizeof(sreg));
- if ( (rc = read_ulong(ea.mem.seg, ea.mem.off+0,
- &limit, 2, ctxt, ops)) ||
- (rc = read_ulong(ea.mem.seg, ea.mem.off+2,
- &base, mode_64bit() ? 8 : 4, ctxt, ops)) )
- goto done;
- generate_exception_if(!is_canonical_address(base), EXC_GP, 0);
- sreg.base = base;
- sreg.limit = limit;
- if ( !mode_64bit() && op_bytes == 2 )
- sreg.base &= 0xffffff;
- if ( (rc = ops->write_segment(seg, &sreg, ctxt)) )
- goto done;
- break;
- case 4: /* smsw */
- generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
- if ( ea.type == OP_MEM )
+ switch ( modrm_reg & 7 )
{
- fail_if(!ops->write);
- d |= Mov; /* force writeback */
- ea.bytes = 2;
+ case 0: /* sgdt */
+ case 1: /* sidt */
+ generate_exception_if(ea.type != OP_MEM, EXC_UD);
+ generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
+ fail_if(!ops->read_segment || !ops->write);
+ if ( (rc = ops->read_segment(seg, &sreg, ctxt)) )
+ goto done;
+ if ( mode_64bit() )
+ op_bytes = 8;
+ else if ( op_bytes == 2 )
+ {
+ sreg.base &= 0xffffff;
+ op_bytes = 4;
+ }
+ if ( (rc = ops->write(ea.mem.seg, ea.mem.off, &sreg.limit,
+ 2, ctxt)) != X86EMUL_OKAY ||
+ (rc = ops->write(ea.mem.seg, ea.mem.off + 2, &sreg.base,
+ op_bytes, ctxt)) != X86EMUL_OKAY )
+ goto done;
+ break;
+ case 2: /* lgdt */
+ case 3: /* lidt */
+ generate_exception_if(!mode_ring0(), EXC_GP, 0);
+ generate_exception_if(ea.type != OP_MEM, EXC_UD);
+ fail_if(ops->write_segment == NULL);
+ memset(&sreg, 0, sizeof(sreg));
+ if ( (rc = read_ulong(ea.mem.seg, ea.mem.off+0,
+ &limit, 2, ctxt, ops)) ||
+ (rc = read_ulong(ea.mem.seg, ea.mem.off+2,
+ &base, mode_64bit() ? 8 : 4, ctxt, ops)) )
+ goto done;
+ generate_exception_if(!is_canonical_address(base), EXC_GP, 0);
+ sreg.base = base;
+ sreg.limit = limit;
+ if ( !mode_64bit() && op_bytes == 2 )
+ sreg.base &= 0xffffff;
+ if ( (rc = ops->write_segment(seg, &sreg, ctxt)) )
+ goto done;
+ break;
+ case 4: /* smsw */
+ generate_exception_if(umip_active(ctxt, ops), EXC_GP, 0);
+ if ( ea.type == OP_MEM )
+ {
+ fail_if(!ops->write);
+ d |= Mov; /* force writeback */
+ ea.bytes = 2;
+ }
+ else
+ ea.bytes = op_bytes;
+ dst = ea;
+ fail_if(ops->read_cr == NULL);
+ if ( (rc = ops->read_cr(0, &dst.val, ctxt)) )
+ goto done;
+ break;
+ case 6: /* lmsw */
+ fail_if(ops->read_cr == NULL);
+ fail_if(ops->write_cr == NULL);
+ generate_exception_if(!mode_ring0(), EXC_GP, 0);
+ if ( (rc = ops->read_cr(0, &cr0, ctxt)) )
+ goto done;
+ if ( ea.type == OP_REG )
+ cr0w = *ea.reg;
+ else if ( (rc = read_ulong(ea.mem.seg, ea.mem.off,
+ &cr0w, 2, ctxt, ops)) )
+ goto done;
+ /* LMSW can: (1) set bits 0-3; (2) clear bits 1-3. */
+ cr0 = (cr0 & ~0xe) | (cr0w & 0xf);
+ if ( (rc = ops->write_cr(0, cr0, ctxt)) )
+ goto done;
+ break;
+ case 7: /* invlpg */
+ generate_exception_if(!mode_ring0(), EXC_GP, 0);
+ generate_exception_if(ea.type != OP_MEM, EXC_UD);
+ fail_if(ops->invlpg == NULL);
+ if ( (rc = ops->invlpg(ea.mem.seg, ea.mem.off, ctxt)) )
+ goto done;
+ break;
+ default:
+ goto cannot_emulate;
}
- else
- ea.bytes = op_bytes;
- dst = ea;
- fail_if(ops->read_cr == NULL);
- if ( (rc = ops->read_cr(0, &dst.val, ctxt)) )
- goto done;
- break;
- case 6: /* lmsw */
- fail_if(ops->read_cr == NULL);
- fail_if(ops->write_cr == NULL);
- generate_exception_if(!mode_ring0(), EXC_GP, 0);
- if ( (rc = ops->read_cr(0, &cr0, ctxt)) )
- goto done;
- if ( ea.type == OP_REG )
- cr0w = *ea.reg;
- else if ( (rc = read_ulong(ea.mem.seg, ea.mem.off,
- &cr0w, 2, ctxt, ops)) )
- goto done;
- /* LMSW can: (1) set bits 0-3; (2) clear bits 1-3. */
- cr0 = (cr0 & ~0xe) | (cr0w & 0xf);
- if ( (rc = ops->write_cr(0, cr0, ctxt)) )
- goto done;
- break;
- case 7: /* invlpg */
- generate_exception_if(!mode_ring0(), EXC_GP, 0);
- generate_exception_if(ea.type != OP_MEM, EXC_UD);
- fail_if(ops->invlpg == NULL);
- if ( (rc = ops->invlpg(ea.mem.seg, ea.mem.off, ctxt)) )
- goto done;
- break;
- default:
- goto cannot_emulate;
}
break;
}
--
2.1.4
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next reply other threads:[~2017-09-04 17:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-04 17:21 Andrew Cooper [this message]
2017-09-04 17:34 ` [PATCH RFC v2] x86/emul: Fix the handling of unimplemented Grp7 instructions Andrew Cooper
2017-09-05 6:57 ` Jan Beulich
2017-09-05 7:34 ` Andrew Cooper
2017-09-05 9:43 ` Jan Beulich
2017-09-05 9:53 ` Andrew Cooper
2017-09-05 10:07 ` Jan Beulich
2017-09-05 8:41 ` [PATCH v3] " Andrew Cooper
2017-09-05 10:23 ` Jan Beulich
2017-09-05 17:02 ` Petre Ovidiu PIRCALABU
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