All of lore.kernel.org
 help / color / mirror / Atom feed
From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: Mark Brown <broonie@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 5/5] arm64: bti: Provide Kconfig for kernel mode BTI
Date: Fri, 27 Mar 2020 19:21:07 +0000	[thread overview]
Message-ID: <20200327192107.18394-6-broonie@kernel.org> (raw)
In-Reply-To: <20200327192107.18394-1-broonie@kernel.org>

Now that all the code is in place provide a Kconfig option allowing users
to enable BTI for the kernel if their toolchain supports it, defaulting it
on since this has security benefits. This is a separate configuration
option since we currently don't support secondary CPUs that lack BTI if
the boot CPU supports it.

Current testing appears to show an issue with GCC which causes it to
emit unsuitable landing pads for function entries in some cases, until
this issue is understood and either our usage fixed or a suitable
version of GCC is identified the feature is marked as incompatible with
GCC.  No issues have been identified with clang.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/Kconfig | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 00cb4db4beab..25bb0931b2ba 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1607,6 +1607,24 @@ config ARM64_BTI
 	  BTI, such binaries can still run, but you get no additional
 	  enforcement of branch destinations.
 
+config ARM64_BTI_KERNEL
+	bool "Use Branch Target Identification for kernel"
+	default y
+	depends on ARM64_BTI
+	depends on ARM64_PTR_AUTH
+	depends on CC_HAS_BRANCH_PROT_PAC_RET_BTI
+	depends on !CC_IS_GCC
+	depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS)
+	help
+	  Build the kernel with Branch Target Identification annotations
+	  and enable enforcement of this for kernel code. When this option
+	  is enabled and the system supports BTI all kernel code including
+	  modular code must have BTI enabled.
+
+config CC_HAS_BRANCH_PROT_PAC_RET_BTI
+	# GCC 9 or later, clang 8 or later
+	def_bool $(cc-option,-mbranch-protection=pac-ret+leaf+bti)
+
 config ARM64_E0PD
 	bool "Enable support for E0PD"
 	default y
-- 
2.20.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2020-03-27 19:22 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-27 19:21 [PATCH 0/5] arm64: Initial BTI kernel support Mark Brown
2020-03-27 19:21 ` [PATCH 1/5] arm64: bti: Support building kernel C code using BTI Mark Brown
2020-03-28 21:14   ` Kees Cook
2020-03-30 11:33     ` Mark Brown
2020-03-30 18:06       ` Kees Cook
2020-03-31 15:21         ` Mark Brown
2020-03-27 19:21 ` [PATCH 2/5] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI Mark Brown
2020-03-27 19:21 ` [PATCH 3/5] arm64: Set GP bit in kernel page tables to enable BTI for the kernel Mark Brown
2020-03-27 19:21 ` [PATCH 4/5] arm64: mm: Mark module text as guarded pages Mark Brown
2020-03-27 19:21 ` Mark Brown [this message]
2020-03-28 21:19   ` [PATCH 5/5] arm64: bti: Provide Kconfig for kernel mode BTI Kees Cook

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=20200327192107.18394-6-broonie@kernel.org \
    --to=broonie@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=keescook@chromium.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=will@kernel.org \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.