[RFC 2/3] mm/vma: Introduce VM_ACCESS_FLAGS

From: Anshuman Khandual
Date: Mon Mar 02 2020 - 01:48:32 EST

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There are many places where all basic VMA access flags (read, write, exec)
are initialized or checked against as a group. One such example is during
page fault. Existing vma_is_accessible() wrapper already creates the notion
of VMA accessibility as a group access permissions. Hence lets just create
VM_ACCESS_FLAGS (VM_READ|VM_WRITE|VM_EXEC) which will not only reduce code
duplication but also extend the VMA accessibility concept in general.

Cc: Russell King <linux@xxxxxxxxxxxxxxx>
CC: Catalin Marinas <catalin.marinas@xxxxxxx>
CC: Mark Salter <msalter@xxxxxxxxxx>
Cc: Nick Hu <nickhu@xxxxxxxxxxxxx>
CC: Ley Foon Tan <ley.foon.tan@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: Guan Xuetao <gxt@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Rob Springer <rspringer@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-c6x-dev@xxxxxxxxxxxxx
Cc: nios2-dev@xxxxxxxxxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-s390@xxxxxxxxxxxxxxx
Cc: linux-sh@xxxxxxxxxxxxxxx
Cc: devel@xxxxxxxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
arch/arm/mm/fault.c | 2 +-
arch/arm64/mm/fault.c | 2 +-
arch/c6x/include/asm/processor.h | 2 +-
arch/nds32/mm/fault.c | 2 +-
arch/nios2/include/asm/processor.h | 2 +-
arch/powerpc/mm/book3s64/pkeys.c | 2 +-
arch/s390/mm/fault.c | 2 +-
arch/sh/include/asm/processor_64.h | 2 +-
arch/unicore32/mm/fault.c | 2 +-
arch/x86/mm/pkeys.c | 2 +-
drivers/staging/gasket/gasket_core.c | 2 +-
include/linux/mm.h | 4 +++-
mm/mmap.c | 4 ++--
mm/mprotect.c | 7 +++----
14 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index bd0f4821f7e1..2c71028d9d6b 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -189,7 +189,7 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
*/
static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
{
- unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+ unsigned int mask = VM_ACCESS_FLAGS;

if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
mask = VM_WRITE;
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 85566d32958f..63f31206a12e 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -445,7 +445,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
const struct fault_info *inf;
struct mm_struct *mm = current->mm;
vm_fault_t fault, major = 0;
- unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
+ unsigned long vm_flags = VM_ACCESS_FLAGS;
unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

if (kprobe_page_fault(regs, esr))
diff --git a/arch/c6x/include/asm/processor.h b/arch/c6x/include/asm/processor.h
index 1456f5e11de3..77372b8c28d7 100644
--- a/arch/c6x/include/asm/processor.h
+++ b/arch/c6x/include/asm/processor.h
@@ -57,7 +57,7 @@ struct thread_struct {
}

#define INIT_MMAP { \
- &init_mm, 0, 0, NULL, PAGE_SHARED, VM_READ | VM_WRITE | VM_EXEC, 1, \
+ &init_mm, 0, 0, NULL, PAGE_SHARED, VM_ACCESS_FLAGS, 1, \
NULL, NULL }

#define task_pt_regs(task) \
diff --git a/arch/nds32/mm/fault.c b/arch/nds32/mm/fault.c
index 906dfb25353c..55387a31bf42 100644
--- a/arch/nds32/mm/fault.c
+++ b/arch/nds32/mm/fault.c
@@ -79,7 +79,7 @@ void do_page_fault(unsigned long entry, unsigned long addr,
struct vm_area_struct *vma;
int si_code;
vm_fault_t fault;
- unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+ unsigned int mask = VM_ACCESS_FLAGS;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);
diff --git a/arch/nios2/include/asm/processor.h b/arch/nios2/include/asm/processor.h
index 94bcb86f679f..fbfb3ab14cfc 100644
--- a/arch/nios2/include/asm/processor.h
+++ b/arch/nios2/include/asm/processor.h
@@ -51,7 +51,7 @@ struct thread_struct {
};

#define INIT_MMAP \
- { &init_mm, (0), (0), __pgprot(0x0), VM_READ | VM_WRITE | VM_EXEC }
+ { &init_mm, (0), (0), __pgprot(0x0), VM_ACCESS_FLAGS }

# define INIT_THREAD { \
.kregs = NULL, \
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 59e0ebbd8036..11fd52b24f68 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -315,7 +315,7 @@ int __execute_only_pkey(struct mm_struct *mm)
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
{
/* Do this check first since the vm_flags should be hot */
- if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+ if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
return false;

return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7b0bb475c166..b2cb3c0d0e1a 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -584,7 +584,7 @@ void do_dat_exception(struct pt_regs *regs)
int access;
vm_fault_t fault;

- access = VM_READ | VM_EXEC | VM_WRITE;
+ access = VM_ACCESS_FLAGS;
fault = do_exception(regs, access);
if (unlikely(fault))
do_fault_error(regs, access, fault);
diff --git a/arch/sh/include/asm/processor_64.h b/arch/sh/include/asm/processor_64.h
index 53efc9f51ef1..3b8187284e3f 100644
--- a/arch/sh/include/asm/processor_64.h
+++ b/arch/sh/include/asm/processor_64.h
@@ -121,7 +121,7 @@ struct thread_struct {
};

#define INIT_MMAP \
-{ &init_mm, 0, 0, NULL, PAGE_SHARED, VM_READ | VM_WRITE | VM_EXEC, 1, NULL, NULL }
+{ &init_mm, 0, 0, NULL, PAGE_SHARED, VM_ACCESS_FLAGS, 1, NULL, NULL }

#define INIT_THREAD { \
.sp = sizeof(init_stack) + \
diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
index 76342de9cf8c..fc27c274d358 100644
--- a/arch/unicore32/mm/fault.c
+++ b/arch/unicore32/mm/fault.c
@@ -149,7 +149,7 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
*/
static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
{
- unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+ unsigned int mask = VM_ACCESS_FLAGS;

if (!(fsr ^ 0x12)) /* write? */
mask = VM_WRITE;
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index c6f84c0b5d7a..8873ed1438a9 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -63,7 +63,7 @@ int __execute_only_pkey(struct mm_struct *mm)
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
{
/* Do this check first since the vm_flags should be hot */
- if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+ if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
return false;
if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey)
return false;
diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
index be6b50f454b4..81bb7d58dc49 100644
--- a/drivers/staging/gasket/gasket_core.c
+++ b/drivers/staging/gasket/gasket_core.c
@@ -689,7 +689,7 @@ static bool gasket_mmap_has_permissions(struct gasket_dev *gasket_dev,

/* Make sure that no wrong flags are set. */
requested_permissions =
- (vma->vm_flags & (VM_WRITE | VM_READ | VM_EXEC));
+ (vma->vm_flags & VM_ACCESS_FLAGS);
if (requested_permissions & ~(bar_permissions)) {
dev_dbg(gasket_dev->dev,
"Attempting to map a region with requested permissions "
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7a764ae6ab68..525026df1e58 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -368,6 +368,8 @@ extern unsigned int kobjsize(const void *objp);
#endif

#define VM_STACK_FLAGS (VM_STACK | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
+#define VM_ACCESS_FLAGS (VM_READ | VM_WRITE | VM_EXEC)
+

/*
* Special vmas that are non-mergable, non-mlock()able.
@@ -558,7 +560,7 @@ static inline bool vma_is_anonymous(struct vm_area_struct *vma)

static inline bool vma_is_accessible(struct vm_area_struct *vma)
{
- return vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
+ return vma->vm_flags & VM_ACCESS_FLAGS;
}

#ifdef CONFIG_SHMEM
diff --git a/mm/mmap.c b/mm/mmap.c
index 0d295f49b24d..f9a01763857b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -106,7 +106,7 @@ static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
- (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
+ (VM_ACCESS_FLAGS | VM_SHARED)]) |
pgprot_val(arch_vm_get_page_prot(vm_flags)));

return arch_filter_pgprot(ret);
@@ -1221,7 +1221,7 @@ static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *
return a->vm_end == b->vm_start &&
mpol_equal(vma_policy(a), vma_policy(b)) &&
a->vm_file == b->vm_file &&
- !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
+ !((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
}

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 7a8e84f86831..4921a4211c6b 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -359,7 +359,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
*/
if (arch_has_pfn_modify_check() &&
(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
- (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
+ (newflags & VM_ACCESS_FLAGS) == 0) {
pgprot_t new_pgprot = vm_get_page_prot(newflags);

error = walk_page_range(current->mm, start, end,
@@ -530,15 +530,14 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
* If a permission is not passed to mprotect(), it must be
* cleared from the VMA.
*/
- mask_off_old_flags = VM_READ | VM_WRITE | VM_EXEC |
- VM_FLAGS_CLEAR;
+ mask_off_old_flags = VM_ACCESS_FLAGS | VM_FLAGS_CLEAR;

new_vma_pkey = arch_override_mprotect_pkey(vma, prot, pkey);
newflags = calc_vm_prot_bits(prot, new_vma_pkey);
newflags |= (vma->vm_flags & ~mask_off_old_flags);

/* newflags >> 4 shift VM_MAY% in place of VM_% */
- if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
+ if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
error = -EACCES;
goto out;
}
--
2.20.1

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Next in thread: Vlastimil Babka: "Re: [RFC 2/3] mm/vma: Introduce VM_ACCESS_FLAGS"
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