Without this patch, the MAP_SYNC test case will cause a print_bad_pte
warning on arm64 as follows:
[ 25.542693] BUG: Bad page map in process mapdax333
pte:2e8000448800f53 pmd:41ff5f003
[ 25.546360] page:ffff7e0010220000 refcount:1 mapcount:-1
mapping:ffff8003e29c7440 index:0x0
[ 25.550281] ext4_dax_aops
[ 25.550282] name:"__aaabbbcccddd__"
[ 25.551553] flags: 0x3ffff0000001002(referenced|reserved)
[ 25.555802] raw: 03ffff0000001002 ffff8003dfffa908 0000000000000000
ffff8003e29c7440
[ 25.559446] raw: 0000000000000000 0000000000000000 00000001fffffffe
0000000000000000
[ 25.563075] page dumped because: bad pte
[ 25.564938] addr:0000ffffbe05b000 vm_flags:208000fb
anon_vma:0000000000000000 mapping:ffff8003e29c7440 index:0
[ 25.574272] file:__aaabbbcccddd__ fault:ext4_dax_fault
mmmmap:ext4_file_mmap readpage:0x0
[ 25.578799] CPU: 1 PID: 1180 Comm: mapdax333 Not tainted 5.2.0+ #21
[ 25.581702] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0
02/06/2015
[ 25.585624] Call trace:
[ 25.587008] dump_backtrace+0x0/0x178
[ 25.588799] show_stack+0x24/0x30
[ 25.590328] dump_stack+0xa8/0xcc
[ 25.591901] print_bad_pte+0x18c/0x218
[ 25.593628] unmap_page_range+0x778/0xc00
[ 25.595506] unmap_single_vma+0x94/0xe8
[ 25.597304] unmap_vmas+0x90/0x108
[ 25.598901] unmap_region+0xc0/0x128
[ 25.600566] __do_munmap+0x284/0x3f0
[ 25.602245] __vm_munmap+0x78/0xe0
[ 25.603820] __arm64_sys_munmap+0x34/0x48
[ 25.605709] el0_svc_common.constprop.0+0x78/0x168
[ 25.607956] el0_svc_handler+0x34/0x90
[ 25.609698] el0_svc+0x8/0xc
[ 25.611103] Disabling lock debugging due to kernel taint
[ 25.613573] BUG: Bad page state in process mapdax333 pfn:448800
[ 25.616359] page:ffff7e0010220000 refcount:0 mapcount:-1
mapping:ffff8003e29c7440 index:0x1
[ 25.620236] ext4_dax_aops
[ 25.620237] name:"__aaabbbcccddd__"
[ 25.621495] flags: 0x3ffff0000000000()
[ 25.624912] raw: 03ffff0000000000 dead000000000100 dead000000000200
ffff8003e29c7440
[ 25.628502] raw: 0000000000000001 0000000000000000 00000000fffffffe
0000000000000000
[ 25.632097] page dumped because: non-NULL mapping
[...]
[ 25.656567] CPU: 1 PID: 1180 Comm: mapdax333 Tainted: G B
5.2.0+ #21
[ 25.660131] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0
02/06/2015
[ 25.663324] Call trace:
[ 25.664466] dump_backtrace+0x0/0x178
[ 25.666163] show_stack+0x24/0x30
[ 25.667721] dump_stack+0xa8/0xcc
[ 25.669270] bad_page+0xf0/0x150
[ 25.670772] free_pages_check_bad+0x84/0xa0
[ 25.672724] free_pcppages_bulk+0x45c/0x708
[ 25.674675] free_unref_page_commit+0xcc/0x100
[ 25.676751] free_unref_page_list+0x13c/0x200
[ 25.678801] release_pages+0x350/0x420
[ 25.680539] free_pages_and_swap_cache+0xf8/0x128
[ 25.682738] tlb_flush_mmu+0x164/0x2b0
[ 25.684485] unmap_page_range+0x648/0xc00
[ 25.686349] unmap_single_vma+0x94/0xe8
[ 25.688131] unmap_vmas+0x90/0x108
[ 25.689739] unmap_region+0xc0/0x128
[ 25.691392] __do_munmap+0x284/0x3f0
[ 25.693079] __vm_munmap+0x78/0xe0
[ 25.694658] __arm64_sys_munmap+0x34/0x48
[ 25.696530] el0_svc_common.constprop.0+0x78/0x168
[ 25.698772] el0_svc_handler+0x34/0x90
[ 25.700512] el0_svc+0x8/0xc
The root cause is in _vm_normal_page, without the PTE_SPECIAL bit,
the return value will be incorrectly set to pfn_to_page(pfn) instead
of NULL. Besides, this patch also rewrite the pmd_mkdevmap to avoid
setting PTE_SPECIAL for pmd
The MAP_SYNC test case is as follows(Provided by Yibo Cai)
$#include <stdio.h>
$#include <string.h>
$#include <unistd.h>
$#include <sys/file.h>
$#include <sys/mman.h>
$#ifndef MAP_SYNC
$#define MAP_SYNC 0x80000
$#endif
/* mount -o dax /dev/pmem0 /mnt */
$#define F "/mnt/__aaabbbcccddd__"
int main(void)
{
int fd;
char buf[4096];
void *addr;
if ((fd = open(F, O_CREAT|O_TRUNC|O_RDWR, 0644)) < 0) {
perror("open1");
return 1;
}
if (write(fd, buf, 4096) != 4096) {
perror("lseek");
return 1;
}
addr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_SYNC,
fd, 0);
if (addr == MAP_FAILED) {
perror("mmap");
printf("did you mount with '-o dax'?\n");
return 1;
}
memset(addr, 0x55, 4096);
if (munmap(addr, 4096) == -1) {
perror("munmap");
return 1;
}
close(fd);
return 0;
}
Fixes: 73b20c84d42d ("arm64: mm: implement pte_devmap support")
Reported-by: Yibo Cai <yibo....@arm.com>
Signed-off-by: Jia He <justin...@arm.com>
Acked-by: Robin Murphy <robin.mur...@arm.com>
---
arch/arm64/include/asm/pgtable.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 5fdcfe237338..e09760ece844 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -209,7 +209,7 @@ static inline pmd_t pmd_mkcont(pmd_t pmd)
static inline pte_t pte_mkdevmap(pte_t pte)
{
- return set_pte_bit(pte, __pgprot(PTE_DEVMAP));
+ return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL));
}
static inline void set_pte(pte_t *ptep, pte_t pte)
@@ -396,7 +396,10 @@ static inline int pmd_protnone(pmd_t pmd)
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define pmd_devmap(pmd) pte_devmap(pmd_pte(pmd))
#endif
-#define pmd_mkdevmap(pmd) pte_pmd(pte_mkdevmap(pmd_pte(pmd)))
+static inline pmd_t pmd_mkdevmap(pmd_t pmd)
+{
+ return pte_pmd(set_pte_bit(pmd_pte(pmd), __pgprot(PTE_DEVMAP)));
+}
#define __pmd_to_phys(pmd) __pte_to_phys(pmd_pte(pmd))
#define __phys_to_pmd_val(phys) __phys_to_pte_val(phys)
--
2.17.1
