LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	catalin.marinas@arm.com, christoffer.dall@arm.com,
	drjones@redhat.com, marc.zyngier@arm.com, mark.rutland@arm.com,
	ramana.radhakrishnan@arm.com, suzuki.poulose@arm.com,
	will.deacon@arm.com, awallis@codeaurora.org
Subject: [PATCHv4 08/10] arm64: perf: strip PAC when unwinding userspace
Date: Thu,  3 May 2018 14:20:29 +0100	[thread overview]
Message-ID: <20180503132031.25705-9-mark.rutland@arm.com> (raw)
In-Reply-To: <20180503132031.25705-1-mark.rutland@arm.com>

When the kernel is unwinding userspace callchains, we can't expect that
the userspace consumer of these callchains has the data necessary to
strip the PAC from the stored LR.

This patch has the kernel strip the PAC from user stackframes when the
in-kernel unwinder is used. This only affects the LR value, and not the
FP.

This only affects the in-kernel unwinder. When userspace performs
unwinding, it is up to userspace to strip PACs as necessary (which can
be determined from DWARF information).

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/include/asm/pointer_auth.h | 7 +++++++
 arch/arm64/kernel/perf_callchain.c    | 5 ++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 0263b87f95f7..284db173ae5d 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -65,6 +65,12 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old,
  */
 #define ptrauth_pac_mask() 	GENMASK(54, VA_BITS)
 
+/* Only valid for EL0 TTBR0 instruction pointers */
+static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
+{
+	return ptr & ~ptrauth_pac_mask();
+}
+
 #define mm_ctx_ptrauth_init(ctx) \
 	ptrauth_keys_init(&(ctx)->ptrauth_keys)
 
@@ -75,6 +81,7 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old,
 	ptrauth_keys_dup(&(oldctx)->ptrauth_keys, &(newctx)->ptrauth_keys)
 
 #else
+#define ptrauth_strip_insn_pac(lr)	(lr)
 #define mm_ctx_ptrauth_init(ctx)
 #define mm_ctx_ptrauth_switch(ctx)
 #define mm_ctx_ptrauth_dup(oldctx, newctx)
diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
index bcafd7dcfe8b..928204f6ab08 100644
--- a/arch/arm64/kernel/perf_callchain.c
+++ b/arch/arm64/kernel/perf_callchain.c
@@ -35,6 +35,7 @@ user_backtrace(struct frame_tail __user *tail,
 {
 	struct frame_tail buftail;
 	unsigned long err;
+	unsigned long lr;
 
 	/* Also check accessibility of one struct frame_tail beyond */
 	if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
@@ -47,7 +48,9 @@ user_backtrace(struct frame_tail __user *tail,
 	if (err)
 		return NULL;
 
-	perf_callchain_store(entry, buftail.lr);
+	lr = ptrauth_strip_insn_pac(buftail.lr);
+
+	perf_callchain_store(entry, lr);
 
 	/*
 	 * Frame pointers should strictly progress back up the stack
-- 
2.11.0

  parent reply	other threads:[~2018-05-03 13:21 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-03 13:20 [PATCHv4 00/10] ARMv8.3 pointer authentication userspace support Mark Rutland
2018-05-03 13:20 ` [PATCHv4 01/10] arm64: add pointer authentication register bits Mark Rutland
2018-05-03 13:20 ` [PATCHv4 02/10] arm64/kvm: consistently handle host HCR_EL2 flags Mark Rutland
2018-05-03 13:20 ` [PATCHv4 03/10] arm64/kvm: hide ptrauth from guests Mark Rutland
2018-05-03 13:20 ` [PATCHv4 04/10] arm64: Don't trap host pointer auth use to EL2 Mark Rutland
2018-05-03 13:20 ` [PATCHv4 05/10] arm64/cpufeature: detect pointer authentication Mark Rutland
2018-05-23  8:48   ` Suzuki K Poulose
2018-05-25 10:01     ` Mark Rutland
2018-07-04 16:09       ` Will Deacon
2018-05-03 13:20 ` [PATCHv4 06/10] arm64: add basic pointer authentication support Mark Rutland
2018-05-22 19:08   ` Adam Wallis
2018-05-23  8:42   ` Suzuki K Poulose
2018-05-25 10:18     ` Mark Rutland
2018-06-08 13:11   ` Kristina Martsenko
2018-05-03 13:20 ` [PATCHv4 07/10] arm64: expose user PAC bit positions via ptrace Mark Rutland
2018-05-03 13:20 ` Mark Rutland [this message]
2018-05-03 13:20 ` [PATCHv4 09/10] arm64: enable pointer authentication Mark Rutland
2018-05-03 13:20 ` [PATCHv4 10/10] arm64: docs: document " Mark Rutland
2018-07-04 16:12 ` [PATCHv4 00/10] ARMv8.3 pointer authentication userspace support 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=20180503132031.25705-9-mark.rutland@arm.com \
    --to=mark.rutland@arm.com \
    --cc=awallis@codeaurora.org \
    --cc=catalin.marinas@arm.com \
    --cc=christoffer.dall@arm.com \
    --cc=drjones@redhat.com \
    --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=ramana.radhakrishnan@arm.com \
    --cc=suzuki.poulose@arm.com \
    --cc=will.deacon@arm.com \
    --subject='Re: [PATCHv4 08/10] arm64: perf: strip PAC when unwinding userspace' \
    /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

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).