From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
MPX is being removed from the kernel due to a lack of support
in the toolchain going forward (gcc).
There are two hooks into the generic mm code that MPX uses: one
for ~munmap() and the other at execve() time. Remove them,
eliminating MPX from generic mm code.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/mmu_context.h | 31 -------------------------------
fs/exec.c | 1 -
include/asm-generic/mm_hooks.h | 11 -----------
mm/mmap.c | 6 ------
4 files changed, 49 deletions(-)
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 0ca5061..61363e7 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -12,7 +12,6 @@
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/paravirt.h>
-#include <asm/mpx.h>
extern atomic64_t last_mm_ctx_id;
@@ -253,36 +252,6 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
}
#endif
-static inline void arch_bprm_mm_init(struct mm_struct *mm,
- struct vm_area_struct *vma)
-{
- mpx_mm_init(mm);
-}
-
-static inline void arch_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
-{
- /*
- * mpx_notify_unmap() goes and reads a rarely-hot
- * cacheline in the mm_struct. That can be expensive
- * enough to be seen in profiles.
- *
- * The mpx_notify_unmap() call and its contents have been
- * observed to affect munmap() performance on hardware
- * where MPX is not present.
- *
- * The unlikely() optimizes for the fast case: no MPX
- * in the CPU, or no MPX use in the process. Even if
- * we get this wrong (in the unlikely event that MPX
- * is widely enabled on some system) the overhead of
- * MPX itself (reading bounds tables) is expected to
- * overwhelm the overhead of getting this unlikely()
- * consistently wrong.
- */
- if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX)))
- mpx_notify_unmap(mm, vma, start, end);
-}
-
/*
* We only want to enforce protection keys on the current process
* because we effectively have no access to PKRU for other
diff --git a/fs/exec.c b/fs/exec.c
index fc281b7..cb99ea5 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -317,7 +317,6 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
goto err;
mm->stack_vm = mm->total_vm = 1;
- arch_bprm_mm_init(mm, vma);
up_write(&mm->mmap_sem);
bprm->p = vma->vm_end - sizeof(void *);
return 0;
diff --git a/include/asm-generic/mm_hooks.h b/include/asm-generic/mm_hooks.h
index 8ac4e68..40038d0 100644
--- a/include/asm-generic/mm_hooks.h
+++ b/include/asm-generic/mm_hooks.h
@@ -17,17 +17,6 @@ static inline void arch_exit_mmap(struct mm_struct *mm)
{
}
-static inline void arch_unmap(struct mm_struct *mm,
- struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
-{
-}
-
-static inline void arch_bprm_mm_init(struct mm_struct *mm,
- struct vm_area_struct *vma)
-{
-}
-
static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
bool write, bool execute, bool foreign)
{
diff --git a/mm/mmap.c b/mm/mmap.c
index f901065..ca9f43c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2813,12 +2813,6 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
/* Detach vmas from rbtree */
detach_vmas_to_be_unmapped(mm, vma, prev, end);
- /*
- * mpx unmap needs to be called with mmap_sem held for write.
- * It is safe to call it before unmap_region().
- */
- arch_unmap(mm, vma, start, end);
-
if (downgrade)
downgrade_write(&mm->mmap_sem);
--
2.7.4
