From: Kristina Martsenko <kristina.martsenko@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Adam Wallis <awallis@codeaurora.org>,
Amit Kachhap <amit.kachhap@arm.com>,
Andrew Jones <drjones@redhat.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Christoffer Dall <christoffer.dall@arm.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave P Martin <dave.martin@arm.com>,
Jacob Bramley <jacob.bramley@arm.com>,
Kees Cook <keescook@chromium.org>,
Marc Zyngier <marc.zyngier@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Will Deacon <will.deacon@arm.com>,
kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
Subject: [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests
Date: Fri, 7 Dec 2018 18:39:22 +0000 [thread overview]
Message-ID: <20181207183931.4285-5-kristina.martsenko@arm.com> (raw)
In-Reply-To: <20181207183931.4285-1-kristina.martsenko@arm.com>
From: Mark Rutland <mark.rutland@arm.com>
In subsequent patches we're going to expose ptrauth to the host kernel
and userspace, but things are a bit trickier for guest kernels. For the
time being, let's hide ptrauth from KVM guests.
Regardless of how well-behaved the guest kernel is, guest userspace
could attempt to use ptrauth instructions, triggering a trap to EL2,
resulting in noise from kvm_handle_unknown_ec(). So let's write up a
handler for the PAC trap, which silently injects an UNDEF into the
guest, as if the feature were really missing.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
arch/arm64/kvm/handle_exit.c | 18 ++++++++++++++++++
arch/arm64/kvm/sys_regs.c | 8 ++++++++
2 files changed, 26 insertions(+)
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 35a81bebd02b..ab35929dcb3c 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -173,6 +173,23 @@ static int handle_sve(struct kvm_vcpu *vcpu, struct kvm_run *run)
return 1;
}
+/*
+ * Guest usage of a ptrauth instruction (which the guest EL1 did not turn into
+ * a NOP).
+ */
+static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ /*
+ * We don't currently support ptrauth in a guest, and we mask the ID
+ * registers to prevent well-behaved guests from trying to make use of
+ * it.
+ *
+ * Inject an UNDEF, as if the feature really isn't present.
+ */
+ kvm_inject_undefined(vcpu);
+ return 1;
+}
+
static exit_handle_fn arm_exit_handlers[] = {
[0 ... ESR_ELx_EC_MAX] = kvm_handle_unknown_ec,
[ESR_ELx_EC_WFx] = kvm_handle_wfx,
@@ -195,6 +212,7 @@ static exit_handle_fn arm_exit_handlers[] = {
[ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug,
[ESR_ELx_EC_BRK64] = kvm_handle_guest_debug,
[ESR_ELx_EC_FP_ASIMD] = handle_no_fpsimd,
+ [ESR_ELx_EC_PAC] = kvm_handle_ptrauth,
};
static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 22fbbdbece3c..1ca592d38c3c 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1040,6 +1040,14 @@ static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
kvm_debug("SVE unsupported for guests, suppressing\n");
val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
+ } else if (id == SYS_ID_AA64ISAR1_EL1) {
+ const u64 ptrauth_mask = (0xfUL << ID_AA64ISAR1_APA_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_API_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_GPA_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_GPI_SHIFT);
+ if (val & ptrauth_mask)
+ kvm_debug("ptrauth unsupported for guests, suppressing\n");
+ val &= ~ptrauth_mask;
} else if (id == SYS_ID_AA64MMFR1_EL1) {
if (val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))
kvm_debug("LORegions unsupported for guests, suppressing\n");
--
2.11.0
next prev parent reply other threads:[~2018-12-07 18:40 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-07 18:39 [PATCH v6 00/13] ARMv8.3 pointer authentication userspace support Kristina Martsenko
2018-12-07 18:39 ` [PATCH v6 01/13] arm64: add comments about EC exception levels Kristina Martsenko
2018-12-09 14:34 ` Richard Henderson
2018-12-07 18:39 ` [PATCH v6 02/13] arm64: add pointer authentication register bits Kristina Martsenko
2018-12-09 14:24 ` Richard Henderson
2018-12-10 19:54 ` Kristina Martsenko
2018-12-11 20:08 ` Will Deacon
2018-12-07 18:39 ` [PATCH v6 03/13] arm64/kvm: consistently handle host HCR_EL2 flags Kristina Martsenko
2018-12-08 10:31 ` Marc Zyngier
2018-12-09 14:35 ` Richard Henderson
2018-12-07 18:39 ` Kristina Martsenko [this message]
2018-12-08 10:32 ` [PATCH v6 04/13] arm64/kvm: hide ptrauth from guests Marc Zyngier
2018-12-09 14:53 ` Richard Henderson
2018-12-10 20:12 ` Kristina Martsenko
2018-12-10 20:22 ` Richard Henderson
2018-12-10 20:30 ` Kristina Martsenko
2018-12-19 15:21 ` Peter Maydell
2018-12-07 18:39 ` [PATCH v6 05/13] arm64: Don't trap host pointer auth use to EL2 Kristina Martsenko
2018-12-09 14:54 ` Richard Henderson
2018-12-07 18:39 ` [PATCH v6 06/13] arm64/cpufeature: detect pointer authentication Kristina Martsenko
2018-12-09 14:58 ` Richard Henderson
2018-12-07 18:39 ` [PATCH v6 07/13] arm64: add basic pointer authentication support Kristina Martsenko
2018-12-09 14:59 ` Richard Henderson
2019-01-03 20:29 ` Pavel Machek
2019-01-04 9:21 ` Marc Zyngier
2019-01-04 9:33 ` Pavel Machek
2019-01-04 18:02 ` Mark Rutland
2018-12-07 18:39 ` [PATCH v6 08/13] arm64: expose user PAC bit positions via ptrace Kristina Martsenko
2018-12-09 15:03 ` Richard Henderson
2018-12-09 15:41 ` Richard Henderson
2018-12-10 12:03 ` Catalin Marinas
2018-12-10 14:22 ` Richard Henderson
2018-12-10 14:29 ` Will Deacon
2018-12-10 16:09 ` Catalin Marinas
2018-12-07 18:39 ` [PATCH v6 09/13] arm64: perf: strip PAC when unwinding userspace Kristina Martsenko
2018-12-07 18:39 ` [PATCH v6 10/13] arm64: add prctl control for resetting ptrauth keys Kristina Martsenko
2018-12-12 15:22 ` Dave Martin
2018-12-07 18:39 ` [PATCH v6 11/13] arm64: add ptrace regsets for ptrauth key management Kristina Martsenko
2018-12-12 15:23 ` Dave Martin
2018-12-07 18:39 ` [PATCH v6 12/13] arm64: enable pointer authentication Kristina Martsenko
2018-12-07 18:39 ` [PATCH v6 13/13] arm64: docs: document " Kristina Martsenko
2018-12-12 19:35 ` [PATCH v6 00/13] ARMv8.3 pointer authentication userspace support Will Deacon
2018-12-13 18:01 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181207183931.4285-5-kristina.martsenko@arm.com \
--to=kristina.martsenko@arm.com \
--cc=amit.kachhap@arm.com \
--cc=ard.biesheuvel@linaro.org \
--cc=awallis@codeaurora.org \
--cc=catalin.marinas@arm.com \
--cc=christoffer.dall@arm.com \
--cc=dave.martin@arm.com \
--cc=drjones@redhat.com \
--cc=gorcunov@gmail.com \
--cc=jacob.bramley@arm.com \
--cc=keescook@chromium.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=marc.zyngier@arm.com \
--cc=mark.rutland@arm.com \
--cc=ramana.radhakrishnan@arm.com \
--cc=richard.henderson@linaro.org \
--cc=suzuki.poulose@arm.com \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).