The patch titled
Subject: x86: mm: avoid allocating struct mm_struct on the stack
has been removed from the -mm tree. Its filename was
x86-mm-avoid-allocating-struct-mm_struct-on-the-stack.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Steven Price <steven.price@xxxxxxx>
Subject: x86: mm: avoid allocating struct mm_struct on the stack
struct mm_struct is quite large (~1664 bytes) and so allocating on the
stack may cause problems as the kernel stack size is small.
Since ptdump_walk_pgd_level_core() was only allocating the structure so
that it could modify the pgd argument we can instead introduce a pgd
override in struct mm_walk and pass this down the call stack to where it
is needed.
Since the correct mm_struct is now being passed down, it is now also
unnecessary to take the mmap_sem semaphore because ptdump_walk_pgd() will
now take the semaphore on the real mm.
[steven.price@xxxxxxx: restore missed arm64 changes]
Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@xxxxxxx
Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@xxxxxxx
Signed-off-by: Steven Price <steven.price@xxxxxxx>
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Alexandre Ghiti <alex@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: "Liang, Kan" <kan.liang@xxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Zong Li <zong.li@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/mm/dump.c | 4 ++--
arch/x86/mm/debug_pagetables.c | 10 ++--------
arch/x86/mm/dump_pagetables.c | 18 +++++++-----------
include/linux/pagewalk.h | 3 +++
include/linux/ptdump.h | 2 +-
mm/pagewalk.c | 7 ++++++-
mm/ptdump.c | 4 ++--
7 files changed, 23 insertions(+), 25 deletions(-)
--- a/arch/arm64/mm/dump.c~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/arch/arm64/mm/dump.c
@@ -323,7 +323,7 @@ void ptdump_walk(struct seq_file *s, str
}
};
- ptdump_walk_pgd(&st.ptdump, info->mm);
+ ptdump_walk_pgd(&st.ptdump, info->mm, NULL);
}
static void ptdump_initialize(void)
@@ -361,7 +361,7 @@ void ptdump_check_wx(void)
}
};
- ptdump_walk_pgd(&st.ptdump, &init_mm);
+ ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
if (st.wx_pages || st.uxn_pages)
pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
--- a/arch/x86/mm/debug_pagetables.c~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/arch/x86/mm/debug_pagetables.c
@@ -15,11 +15,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump);
static int ptdump_curknl_show(struct seq_file *m, void *v)
{
- if (current->mm->pgd) {
- down_read(¤t->mm->mmap_sem);
+ if (current->mm->pgd)
ptdump_walk_pgd_level_debugfs(m, current->mm, false);
- up_read(¤t->mm->mmap_sem);
- }
return 0;
}
@@ -28,11 +25,8 @@ DEFINE_SHOW_ATTRIBUTE(ptdump_curknl);
#ifdef CONFIG_PAGE_TABLE_ISOLATION
static int ptdump_curusr_show(struct seq_file *m, void *v)
{
- if (current->mm->pgd) {
- down_read(¤t->mm->mmap_sem);
+ if (current->mm->pgd)
ptdump_walk_pgd_level_debugfs(m, current->mm, true);
- up_read(¤t->mm->mmap_sem);
- }
return 0;
}
--- a/arch/x86/mm/dump_pagetables.c~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/arch/x86/mm/dump_pagetables.c
@@ -357,7 +357,8 @@ static void note_page(struct ptdump_stat
}
}
-static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
+static void ptdump_walk_pgd_level_core(struct seq_file *m,
+ struct mm_struct *mm, pgd_t *pgd,
bool checkwx, bool dmesg)
{
const struct ptdump_range ptdump_ranges[] = {
@@ -386,12 +387,7 @@ static void ptdump_walk_pgd_level_core(s
.seq = m
};
- struct mm_struct fake_mm = {
- .pgd = pgd
- };
- init_rwsem(&fake_mm.mmap_sem);
-
- ptdump_walk_pgd(&st.ptdump, &fake_mm);
+ ptdump_walk_pgd(&st.ptdump, mm, pgd);
if (!checkwx)
return;
@@ -404,7 +400,7 @@ static void ptdump_walk_pgd_level_core(s
void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm)
{
- ptdump_walk_pgd_level_core(m, mm->pgd, false, true);
+ ptdump_walk_pgd_level_core(m, mm, mm->pgd, false, true);
}
void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
@@ -415,7 +411,7 @@ void ptdump_walk_pgd_level_debugfs(struc
if (user && boot_cpu_has(X86_FEATURE_PTI))
pgd = kernel_to_user_pgdp(pgd);
#endif
- ptdump_walk_pgd_level_core(m, pgd, false, false);
+ ptdump_walk_pgd_level_core(m, mm, pgd, false, false);
}
EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
@@ -430,13 +426,13 @@ void ptdump_walk_user_pgd_level_checkwx(
pr_info("x86/mm: Checking user space page tables\n");
pgd = kernel_to_user_pgdp(pgd);
- ptdump_walk_pgd_level_core(NULL, pgd, true, false);
+ ptdump_walk_pgd_level_core(NULL, &init_mm, pgd, true, false);
#endif
}
void ptdump_walk_pgd_level_checkwx(void)
{
- ptdump_walk_pgd_level_core(NULL, INIT_PGD, true, false);
+ ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false);
}
static int __init pt_dump_init(void)
--- a/include/linux/pagewalk.h~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/include/linux/pagewalk.h
@@ -74,6 +74,7 @@ enum page_walk_action {
* mm_walk - walk_page_range data
* @ops: operation to call during the walk
* @mm: mm_struct representing the target process of page table walk
+ * @pgd: pointer to PGD; only valid with no_vma (otherwise set to NULL)
* @vma: vma currently walked (NULL if walking outside vmas)
* @action: next action to perform (see enum page_walk_action)
* @no_vma: walk ignoring vmas (vma will always be NULL)
@@ -84,6 +85,7 @@ enum page_walk_action {
struct mm_walk {
const struct mm_walk_ops *ops;
struct mm_struct *mm;
+ pgd_t *pgd;
struct vm_area_struct *vma;
enum page_walk_action action;
bool no_vma;
@@ -95,6 +97,7 @@ int walk_page_range(struct mm_struct *mm
void *private);
int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
+ pgd_t *pgd,
void *private);
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
void *private);
--- a/include/linux/ptdump.h~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/include/linux/ptdump.h
@@ -17,6 +17,6 @@ struct ptdump_state {
const struct ptdump_range *range;
};
-void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm);
+void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd);
#endif /* _LINUX_PTDUMP_H */
--- a/mm/pagewalk.c~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/mm/pagewalk.c
@@ -206,7 +206,10 @@ static int walk_pgd_range(unsigned long
const struct mm_walk_ops *ops = walk->ops;
int err = 0;
- pgd = pgd_offset(walk->mm, addr);
+ if (walk->pgd)
+ pgd = walk->pgd + pgd_index(addr);
+ else
+ pgd = pgd_offset(walk->mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd)) {
@@ -436,11 +439,13 @@ int walk_page_range(struct mm_struct *mm
*/
int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
unsigned long end, const struct mm_walk_ops *ops,
+ pgd_t *pgd,
void *private)
{
struct mm_walk walk = {
.ops = ops,
.mm = mm,
+ .pgd = pgd,
.private = private,
.no_vma = true
};
--- a/mm/ptdump.c~x86-mm-avoid-allocating-struct-mm_struct-on-the-stack
+++ a/mm/ptdump.c
@@ -122,14 +122,14 @@ static const struct mm_walk_ops ptdump_o
.pte_hole = ptdump_hole,
};
-void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
+void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd)
{
const struct ptdump_range *range = st->range;
down_read(&mm->mmap_sem);
while (range->start != range->end) {
walk_page_range_novma(mm, range->start, range->end,
- &ptdump_ops, st);
+ &ptdump_ops, pgd, st);
range++;
}
up_read(&mm->mmap_sem);
_
Patches currently in -mm which might be from steven.price@xxxxxxx are
