linux-kernel - [PATCH RFT v7 3/9] mm: Introduce ARCH_HAS_USER_SHADOW

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Message-Id: <20240731-clone3-shadow-stack-v7-3-a9532eebfb1d@kernel.org>
Date: Wed, 31 Jul 2024 13:14:09 +0100
From: Mark Brown <broonie@...nel.org>
To: "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>, 
 Deepak Gupta <debug@...osinc.com>, Szabolcs Nagy <Szabolcs.Nagy@....com>, 
 "H.J. Lu" <hjl.tools@...il.com>, Florian Weimer <fweimer@...hat.com>, 
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
 Vincent Guittot <vincent.guittot@...aro.org>, 
 Dietmar Eggemann <dietmar.eggemann@....com>, 
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, 
 Mel Gorman <mgorman@...e.de>, 
 Daniel Bristot de Oliveira <bristot@...hat.com>, 
 Valentin Schneider <vschneid@...hat.com>, 
 Christian Brauner <brauner@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, jannh@...gle.com, bsegall@...gle.com, 
 linux-kselftest@...r.kernel.org, linux-api@...r.kernel.org, 
 Mark Brown <broonie@...nel.org>, Kees Cook <kees@...nel.org>, 
 David Hildenbrand <david@...hat.com>
Subject: [PATCH RFT v7 3/9] mm: Introduce ARCH_HAS_USER_SHADOW_STACK

Since multiple architectures have support for shadow stacks and we need to
select support for this feature in several places in the generic code
provide a generic config option that the architectures can select.

Suggested-by: David Hildenbrand <david@...hat.com>
Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Deepak Gupta <debug@...osinc.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/x86/Kconfig   | 1 +
 fs/proc/task_mmu.c | 2 +-
 include/linux/mm.h | 2 +-
 mm/Kconfig         | 6 ++++++
 4 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 007bab9f2a0e..320e1f411163 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1957,6 +1957,7 @@ config X86_USER_SHADOW_STACK
 	depends on AS_WRUSS
 	depends on X86_64
 	select ARCH_USES_HIGH_VMA_FLAGS
+	select ARCH_HAS_USER_SHADOW_STACK
 	select X86_CET
 	help
 	  Shadow stack protection is a hardware feature that detects function
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5f171ad7b436..0ea49725f524 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -984,7 +984,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
 		[ilog2(VM_UFFD_MINOR)]	= "ui",
 #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
-#ifdef CONFIG_X86_USER_SHADOW_STACK
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
 		[ilog2(VM_SHADOW_STACK)] = "ss",
 #endif
 #ifdef CONFIG_64BIT
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c4b238a20b76..3357625c1db3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -342,7 +342,7 @@ extern unsigned int kobjsize(const void *objp);
 #endif
 #endif /* CONFIG_ARCH_HAS_PKEYS */

-#ifdef CONFIG_X86_USER_SHADOW_STACK
+#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
 /*
  * VM_SHADOW_STACK should not be set with VM_SHARED because of lack of
  * support core mm.
diff --git a/mm/Kconfig b/mm/Kconfig
index b72e7d040f78..3167be663bca 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1263,6 +1263,12 @@ config IOMMU_MM_DATA
 config EXECMEM
 	bool

+config ARCH_HAS_USER_SHADOW_STACK
+	bool
+	help
+	  The architecture has hardware support for userspace shadow call
+          stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
+
 source "mm/damon/Kconfig"

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