[PATCH RFC RFT 1/5] mm: Introduce ARCH_HAS_USER_SHADOW_STACK

[Mark Brown <broonie@kernel.org>]

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@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.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 66bfabae8814..2b72bae0d877 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1926,6 +1926,7 @@ 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 3dd5be96691b..4101e741663a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -697,7 +697,7 @@ 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
 	};
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bf5d0b1b16f4..1728cb77540d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -341,7 +341,7 @@ 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 264a2df5ecf5..aaa2c353ea67 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1258,6 +1258,12 @@ config LOCK_MM_AND_FIND_VMA
 	bool
 	depends on !STACK_GROWSUP
 
+config ARCH_HAS_USER_SHADOW_STACK
+	bool
+	help
+	  The architecture has hardware support for userspace shadow call
+          stacks (eg, x86 CET, arm64 GCS, RISC-V Zisslpcfi).
+
 source "mm/damon/Kconfig"
 
 endmenu

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2.30.2