The previous discussion of the IBT legacy code bitmap is here:
https://lkml.org/lkml/2019/6/6/1032
When CET Indirect Branch Tracking (IBT) is enabled, the processor expects
every branch target is an ENDBR instruction, or the target's address is
marked as legacy in the legacy code bitmap. The bitmap covers the whole
user-mode address space (TASK_SIZE_MAX for 64-bit, TASK_SIZE for IA32),
and each bit represents one page of linear address range.
This patch introduces VM_IBT for the bitmap.
Signed-off-by: Yu-cheng Yu <[email protected]>
---
fs/proc/task_mmu.c | 3 +++
include/linux/mm.h | 8 ++++++++
2 files changed, 11 insertions(+)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 66725e262a77..d707390285d3 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -663,6 +663,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
#endif /* CONFIG_ARCH_HAS_PKEYS */
#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
[ilog2(VM_SHSTK)] = "ss",
+#endif
+#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+ [ilog2(VM_IBT)] = "bt",
#endif
};
size_t i;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 921bae5fa7ab..a8da5bdfd7c9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -299,12 +299,14 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_BIT_6 38 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
#define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
#define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
#define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5)
+#define VM_HIGH_ARCH_6 BIT(VM_HIGH_ARCH_BIT_6)
#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
#ifdef CONFIG_ARCH_HAS_PKEYS
@@ -348,6 +350,12 @@ extern unsigned int kobjsize(const void *objp);
# define VM_SHSTK VM_NONE
#endif
+#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+# define VM_IBT VM_HIGH_ARCH_6
+#else
+# define VM_IBT VM_NONE
+#endif
+
#ifndef VM_GROWSUP
# define VM_GROWSUP VM_NONE
#endif
--
2.17.1
> On Jun 28, 2019, at 12:41 PM, Yu-cheng Yu <[email protected]> wrote:
>
> The previous discussion of the IBT legacy code bitmap is here:
>
> https://lkml.org/lkml/2019/6/6/1032
>
> When CET Indirect Branch Tracking (IBT) is enabled, the processor expects
> every branch target is an ENDBR instruction, or the target's address is
> marked as legacy in the legacy code bitmap. The bitmap covers the whole
> user-mode address space (TASK_SIZE_MAX for 64-bit, TASK_SIZE for IA32),
> and each bit represents one page of linear address range.
>
> This patch introduces VM_IBT for the bitmap.
There’s no need to allocate a bit for this and to clutter up the fault code with special cases. Use _install_special_mapping(), please. If you need to make it more flexible to cover your use case, please do so.