On 04.04.24 01:34, Deepak Gupta wrote:
VM_SHADOW_STACK is defined by x86 as vm flag to mark a shadow stack vma.
x86 uses VM_HIGH_ARCH_5 bit but that limits shadow stack vma to 64bit only.
arm64 follows same path (see links)
To keep things simple, RISC-V follows the same.
This patch adds `ss` for shadow stack in process maps.
Links:
https://lore.kernel.org/lkml/20231009-arm64-gcs-v6-12-78e55deaa4dd@xxxxxxxxxx/#r
Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 3 +++
include/linux/mm.h | 11 ++++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 3f78ebbb795f..d9d63eb74f0d 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -702,6 +702,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
#ifdef CONFIG_X86_USER_SHADOW_STACK
[ilog2(VM_SHADOW_STACK)] = "ss",
+#endif
+#ifdef CONFIG_RISCV_USER_CFI
+ [ilog2(VM_SHADOW_STACK)] = "ss",
#endif
};
size_t i;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f5a97dec5169..64109f6c70f5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -352,7 +352,16 @@ extern unsigned int kobjsize(const void *objp);
* for more details on the guard size.
*/
# define VM_SHADOW_STACK VM_HIGH_ARCH_5
-#else
+#endif
+
+#ifdef CONFIG_RISCV_USER_CFI
+/*
+ * RISC-V is going along with using VM_HIGH_ARCH_5 bit position for shadow stack
+ */
Wow, really?! I could never have guesses that from the code :P
Just drop that comment. Are them semantics the same as for the x86 variant documented?
("VM_SHADOW_STACK should not be set with VM_SHARED because of lack of")
I assume so. So it might now make sense to merge both paths
#if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_RISCV_USER_CFI)
or even introduce some ARCH_HAS_SHADOW_STACK so we can remove these
arch-specific thingies here.
--
Cheers,
David / dhildenb
