AMD Zen3 and newer processors support shadow stack, a feature designed to
protect against ROP (return-oriented programming) attacks in which an attacker
manipulates return addresses on the call stack in order to execute arbitrary
code. To prevent this, shadow stacks can be allocated that are only used by
control transfer and return instructions. When a CALL instruction is issued, it
writes the return address to both the program stack and the shadow stack. When
the subsequent RET instruction is issued, it pops the return address from both
stacks and compares them. If the addresses don't match, a control-protection
exception is raised.
Shadow stack and a related feature, Indirect Branch Tracking (IBT), are
collectively referred to as Control-flow Enforcement Technology (CET). However,
current AMD processors only support shadow stack and not IBT.
This series adds support for shadow stack in SVM guests and builds upon
the support added in the CET guest support patch series [1]. Additional
patches are required to support shadow stack enabled guests in qemu [2]
and glibc [3].
[1]: CET guest support patches (v5)
https://lore.kernel.org/all/[email protected]/
[2]: CET qemu patches
https://patchwork.ozlabs.org/project/qemu-devel/patch/[email protected]/
[3]: glibc tree containing necessary updates
https://gitlab.com/x86-glibc/glibc/-/tree/users/hjl/cet/master/
---
v2:
- Rebased on v3 of the Intel CET virtualization series, dropping the
patch that moved cet_is_msr_accessible to common code as that has
been pulled into the Intel series.
- Minor change removing curly brackets around if statement introduced
in patch 6/6.
v3:
- Rebased on v5 of the Intel CET virtualization series.
- Add patch changing the name of vmplX_ssp SEV-ES save area fields to
plX_ssp.
- Merge this series intended for KVM with the separate guest kernel
patch (now patch 7/8).
- Update MSR passthrough code to conditionally pass through shadow
stack MSRS based on both host and guest support.
- Don't save PL0_SSP, PL1_SSP, and PL2_SSP MSRs on SEV-ES VMRUN as
these are currently unused.
John Allen (8):
KVM: x86: SVM: Emulate reads and writes to shadow stack MSRs
KVM: x86: SVM: Update dump_vmcb with shadow stack save area additions
KVM: x86: SVM: Pass through shadow stack MSRs
KVM: SVM: Rename vmplX_ssp -> plX_ssp
KVM: SVM: Save shadow stack host state on VMRUN
KVM: SVM: Add MSR_IA32_XSS to the GHCB for hypervisor kernel
x86/sev-es: Include XSS value in GHCB CPUID request
KVM: SVM: Add CET features to supported_xss
arch/x86/include/asm/svm.h | 9 +++---
arch/x86/kernel/sev-shared.c | 15 ++++++++++
arch/x86/kvm/svm/sev.c | 21 ++++++++++++--
arch/x86/kvm/svm/svm.c | 53 ++++++++++++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.h | 2 +-
5 files changed, 93 insertions(+), 7 deletions(-)
--
2.39.1
Add shadow stack VMCB save area fields to dump_vmcb. Only include S_CET,
SSP, and ISST_ADDR. Since there currently isn't support to decrypt and
dump the SEV-ES save area, exclude PL0_SSP, PL1_SSP, PL2_SSP, PL3_SSP, and
U_CET which are only inlcuded in the SEV-ES save area.
Signed-off-by: John Allen <[email protected]>
---
arch/x86/kvm/svm/svm.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 57864e83f634..1ac5b51c3f2c 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3386,6 +3386,10 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
"rip:", save->rip, "rflags:", save->rflags);
pr_err("%-15s %016llx %-13s %016llx\n",
"rsp:", save->rsp, "rax:", save->rax);
+ pr_err("%-15s %016llx %-13s %016llx\n",
+ "s_cet:", save->s_cet, "ssp:", save->ssp);
+ pr_err("%-15s %016llx\n",
+ "isst_addr:", save->isst_addr);
pr_err("%-15s %016llx %-13s %016llx\n",
"star:", save01->star, "lstar:", save01->lstar);
pr_err("%-15s %016llx %-13s %016llx\n",
--
2.39.1
Rename SEV-ES save area SSP fields to be consistent with the APM.
Signed-off-by: John Allen <[email protected]>
---
v3:
- New in v3.
---
arch/x86/include/asm/svm.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 72ebd5e4e975..d14536761309 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -361,10 +361,10 @@ struct sev_es_save_area {
struct vmcb_seg ldtr;
struct vmcb_seg idtr;
struct vmcb_seg tr;
- u64 vmpl0_ssp;
- u64 vmpl1_ssp;
- u64 vmpl2_ssp;
- u64 vmpl3_ssp;
+ u64 pl0_ssp;
+ u64 pl1_ssp;
+ u64 pl2_ssp;
+ u64 pl3_ssp;
u64 u_cet;
u8 reserved_0xc8[2];
u8 vmpl;
--
2.39.1