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authorSteven Price <steven.price@arm.com>2020-02-04 04:36:42 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-02-04 06:05:25 +0300
commite47690d756a760579141560ded06ec1020dd85e8 (patch)
treeb81cb0311e9b565111d512b278b77d02b260e2d4
parentf8f0d0b6fa203bfa363d30f34f6fecce9e5cc2f7 (diff)
downloadlinux-e47690d756a760579141560ded06ec1020dd85e8.tar.xz
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@arm.com: restore missed arm64 changes] Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@arm.com Link: http://lkml.kernel.org/r/20200108145710.34314-1-steven.price@arm.com Signed-off-by: Steven Price <steven.price@arm.com> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Hogan <jhogan@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Liang, Kan" <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Burton <paul.burton@mips.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will@kernel.org> Cc: Zong Li <zong.li@sifive.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/arm64/mm/dump.c4
-rw-r--r--arch/x86/mm/debug_pagetables.c10
-rw-r--r--arch/x86/mm/dump_pagetables.c18
-rw-r--r--include/linux/pagewalk.h3
-rw-r--r--include/linux/ptdump.h2
-rw-r--r--mm/pagewalk.c7
-rw-r--r--mm/ptdump.c4
7 files changed, 23 insertions, 25 deletions
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index ef4b3ca1e058..860c00ec8bd3 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -323,7 +323,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
}
};
- 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",
diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
index d0efec713c6c..4a3b62f780b4 100644
--- a/arch/x86/mm/debug_pagetables.c
+++ b/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(&current->mm->mmap_sem);
+ if (current->mm->pgd)
ptdump_walk_pgd_level_debugfs(m, current->mm, false);
- up_read(&current->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(&current->mm->mmap_sem);
+ if (current->mm->pgd)
ptdump_walk_pgd_level_debugfs(m, current->mm, true);
- up_read(&current->mm->mmap_sem);
- }
return 0;
}
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 411f6a758998..64229dad7eab 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -357,7 +357,8 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
}
}
-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(struct seq_file *m, pgd_t *pgd,
.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(struct seq_file *m, pgd_t *pgd,
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(struct seq_file *m, struct mm_struct *mm,
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(void)
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)
diff --git a/include/linux/pagewalk.h b/include/linux/pagewalk.h
index 745a654c6ea7..b1cb6b753abb 100644
--- a/include/linux/pagewalk.h
+++ b/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, unsigned long start,
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);
diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h
index b28f3f2acf90..a67065c403c3 100644
--- a/include/linux/ptdump.h
+++ b/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 */
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 5895ce4f1a85..928df1638c30 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -206,7 +206,10 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
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, unsigned long start,
*/
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
};
diff --git a/mm/ptdump.c b/mm/ptdump.c
index ad18a9839d6f..26208d0d03b7 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -122,14 +122,14 @@ static const struct mm_walk_ops ptdump_ops = {
.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);