From 09d9423d0ef06cc296e55641916c0f5dec39a8c1 Mon Sep 17 00:00:00 2001 From: Jinrong Liang Date: Tue, 25 Jan 2022 17:59:04 +0800 Subject: KVM: x86/emulate: Remove unused "ctxt" of setup_syscalls_segments() The "struct x86_emulate_ctxt *ctxt" parameter of setup_syscalls_segments() is not used, so remove it. No functional change intended. Signed-off-by: Jinrong Liang Message-Id: <20220125095909.38122-15-cloudliang@tencent.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 5719d8cfdbd9..5c5a8fdd708f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2600,8 +2600,7 @@ emulate_shutdown: } static void -setup_syscalls_segments(struct x86_emulate_ctxt *ctxt, - struct desc_struct *cs, struct desc_struct *ss) +setup_syscalls_segments(struct desc_struct *cs, struct desc_struct *ss) { cs->l = 0; /* will be adjusted later */ set_desc_base(cs, 0); /* flat segment */ @@ -2690,7 +2689,7 @@ static int em_syscall(struct x86_emulate_ctxt *ctxt) if (!(efer & EFER_SCE)) return emulate_ud(ctxt); - setup_syscalls_segments(ctxt, &cs, &ss); + setup_syscalls_segments(&cs, &ss); ops->get_msr(ctxt, MSR_STAR, &msr_data); msr_data >>= 32; cs_sel = (u16)(msr_data & 0xfffc); @@ -2758,7 +2757,7 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt) if ((msr_data & 0xfffc) == 0x0) return emulate_gp(ctxt, 0); - setup_syscalls_segments(ctxt, &cs, &ss); + setup_syscalls_segments(&cs, &ss); ctxt->eflags &= ~(X86_EFLAGS_VM | X86_EFLAGS_IF); cs_sel = (u16)msr_data & ~SEGMENT_RPL_MASK; ss_sel = cs_sel + 8; @@ -2795,7 +2794,7 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt) ctxt->mode == X86EMUL_MODE_VM86) return emulate_gp(ctxt, 0); - setup_syscalls_segments(ctxt, &cs, &ss); + setup_syscalls_segments(&cs, &ss); if ((ctxt->rex_prefix & 0x8) != 0x0) usermode = X86EMUL_MODE_PROT64; -- cgit v1.2.3-71-gd317 From 7127fd3677f4827857506f556b2f3eb8856fdf4c Mon Sep 17 00:00:00 2001 From: Jinrong Liang Date: Tue, 25 Jan 2022 17:59:05 +0800 Subject: KVM: x86/emulate: Remove unused "tss_selector" of task_switch_{16, 32}() The "u16 tss_selector" parameter of task_switch_{16, 32}() is not used, so remove it. No functional change intended. Signed-off-by: Jinrong Liang Message-Id: <20220125095909.38122-16-cloudliang@tencent.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 5c5a8fdd708f..b7990defca9c 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3012,8 +3012,7 @@ static int load_state_from_tss16(struct x86_emulate_ctxt *ctxt, return X86EMUL_CONTINUE; } -static int task_switch_16(struct x86_emulate_ctxt *ctxt, - u16 tss_selector, u16 old_tss_sel, +static int task_switch_16(struct x86_emulate_ctxt *ctxt, u16 old_tss_sel, ulong old_tss_base, struct desc_struct *new_desc) { struct tss_segment_16 tss_seg; @@ -3151,8 +3150,7 @@ static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt, return ret; } -static int task_switch_32(struct x86_emulate_ctxt *ctxt, - u16 tss_selector, u16 old_tss_sel, +static int task_switch_32(struct x86_emulate_ctxt *ctxt, u16 old_tss_sel, ulong old_tss_base, struct desc_struct *new_desc) { struct tss_segment_32 tss_seg; @@ -3260,10 +3258,9 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt, old_tss_sel = 0xffff; if (next_tss_desc.type & 8) - ret = task_switch_32(ctxt, tss_selector, old_tss_sel, - old_tss_base, &next_tss_desc); + ret = task_switch_32(ctxt, old_tss_sel, old_tss_base, &next_tss_desc); else - ret = task_switch_16(ctxt, tss_selector, old_tss_sel, + ret = task_switch_16(ctxt, old_tss_sel, old_tss_base, &next_tss_desc); if (ret != X86EMUL_CONTINUE) return ret; -- cgit v1.2.3-71-gd317 From ca85f002258fdac3762c57d12d5e6e401b6a41af Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Tue, 8 Feb 2022 17:34:03 +0800 Subject: KVM: x86/emulator: Defer not-present segment check in __load_segment_descriptor() Per Intel's SDM on the "Instruction Set Reference", when loading segment descriptor, not-present segment check should be after all type and privilege checks. But the emulator checks it first, then #NP is triggered instead of #GP if privilege fails and segment is not present. Put not-present segment check after type and privilege checks in __load_segment_descriptor(). Fixes: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c) Reviewed-by: Sean Christopherson Signed-off-by: Hou Wenlong Message-Id: <52573c01d369f506cadcf7233812427cf7db81a7.1644292363.git.houwenlong.hwl@antgroup.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index b7990defca9c..a6c54b8fdbc7 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1608,11 +1608,6 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, goto exception; } - if (!seg_desc.p) { - err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR; - goto exception; - } - dpl = seg_desc.dpl; switch (seg) { @@ -1652,6 +1647,10 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, case VCPU_SREG_TR: if (seg_desc.s || (seg_desc.type != 1 && seg_desc.type != 9)) goto exception; + if (!seg_desc.p) { + err_vec = NP_VECTOR; + goto exception; + } old_desc = seg_desc; seg_desc.type |= 2; /* busy */ ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc, @@ -1676,6 +1675,11 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, break; } + if (!seg_desc.p) { + err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR; + goto exception; + } + if (seg_desc.s) { /* mark segment as accessed */ if (!(seg_desc.type & 1)) { -- cgit v1.2.3-71-gd317 From 31c66dabaa8a48792469cd2d19a000a0b630aab4 Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Tue, 8 Feb 2022 17:34:04 +0800 Subject: KVM: x86/emulator: Fix wrong privilege check for code segment in __load_segment_descriptor() Code segment descriptor can be loaded by jmp/call/ret, iret and int. The privilege checks are different between those instructions above realmode. Although, the emulator has use x86_transfer_type enumerate to differentiate them, but it is not really used in __load_segment_descriptor(). Note, far jump/call to call gate, task gate or task state segment are not implemented in emulator. As for far jump/call to code segment, if DPL > CPL for conforming code or (RPL > CPL or DPL != CPL) for non-conforming code, it should trigger #GP. The current checks are ok. As for far return, if RPL < CPL or DPL > RPL for conforming code or DPL != RPL for non-conforming code, it should trigger #GP. Outer level return is not implemented above virtual-8086 mode in emulator. So it implies that RPL <= CPL, but the current checks wouldn't trigger #GP if RPL < CPL. As for code segment loading in task switch, if DPL > RPL for conforming code or DPL != RPL for non-conforming code, it should trigger #TS. Since segment selector is loaded before segment descriptor when load state from tss, it implies that RPL = CPL, so the current checks are ok. The only problem in current implementation is missing RPL < CPL check for far return. However, change code to follow the manual is better. Reviewed-by: Sean Christopherson Signed-off-by: Hou Wenlong Message-Id: Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index a6c54b8fdbc7..35e69c2adec2 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1623,14 +1623,29 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, if (!(seg_desc.type & 8)) goto exception; - if (seg_desc.type & 4) { - /* conforming */ - if (dpl > cpl) - goto exception; - } else { - /* nonconforming */ - if (rpl > cpl || dpl != cpl) - goto exception; + /* RET can never return to an inner privilege level. */ + if (transfer == X86_TRANSFER_RET && rpl < cpl) + goto exception; + if (transfer == X86_TRANSFER_RET || transfer == X86_TRANSFER_TASK_SWITCH) { + if (seg_desc.type & 4) { + /* conforming */ + if (dpl > rpl) + goto exception; + } else { + /* nonconforming */ + if (dpl != rpl) + goto exception; + } + } else { /* X86_TRANSFER_CALL_JMP */ + if (seg_desc.type & 4) { + /* conforming */ + if (dpl > cpl) + goto exception; + } else { + /* nonconforming */ + if (rpl > cpl || dpl != cpl) + goto exception; + } } /* in long-mode d/b must be clear if l is set */ if (seg_desc.d && seg_desc.l) { -- cgit v1.2.3-71-gd317 From 1e326ad429784a16b2b34ec296ff4ca7ad42c220 Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Tue, 8 Feb 2022 17:34:05 +0800 Subject: KVM: x86/emulator: Move the unhandled outer privilege level logic of far return into __load_segment_descriptor() Outer-privilege level return is not implemented in emulator, move the unhandled logic into __load_segment_descriptor to make it easier to understand why the checks for RET are incomplete. Suggested-by: Sean Christopherson Signed-off-by: Hou Wenlong Message-Id: <5b7188e6388ac9f4567d14eab32db9adf3e00119.1644292363.git.houwenlong.hwl@antgroup.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) (limited to 'arch/x86/kvm/emulate.c') diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 35e69c2adec2..a60b4d20b309 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1623,9 +1623,14 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, if (!(seg_desc.type & 8)) goto exception; - /* RET can never return to an inner privilege level. */ - if (transfer == X86_TRANSFER_RET && rpl < cpl) - goto exception; + if (transfer == X86_TRANSFER_RET) { + /* RET can never return to an inner privilege level. */ + if (rpl < cpl) + goto exception; + /* Outer-privilege level return is not implemented */ + if (rpl > cpl) + return X86EMUL_UNHANDLEABLE; + } if (transfer == X86_TRANSFER_RET || transfer == X86_TRANSFER_TASK_SWITCH) { if (seg_desc.type & 4) { /* conforming */ @@ -2220,9 +2225,6 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) rc = emulate_pop(ctxt, &cs, ctxt->op_bytes); if (rc != X86EMUL_CONTINUE) return rc; - /* Outer-privilege level return is not implemented */ - if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl) - return X86EMUL_UNHANDLEABLE; rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl, X86_TRANSFER_RET, &new_desc); -- cgit v1.2.3-71-gd317