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ANDROID: 16K: Don't copy data vma for maps/smaps output

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Remove get_data_vma() which made a copy of the original VMA containing
padding and modified vm_end to exclude the trailing padding (if any).

Avoid this copy to avoid races due to stale data relating to
vma->vm_file.

Instead use VMA_PAD_START(vma) directly to get the correct end excluding
padding if any.

Add additional check to verify the padding VMA is as expected and also
check for allocation failure of the pad VMA.

ELFs with padding can be loaded from tmpfs. For simplicity swapped out
shmem accounting in smaps, skips the fast path for read only files and
walks the page table with the range adjusted for padding.

Example output:

===== Maps =====

7ff6306c2000-7ff6306c3000 r--p 00000000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
7ff6306c3000-7ff6306c6000 ---p 00000000 00:00 0                          [page size compat]
7ff6306c6000-7ff6306c7000 r-xp 00004000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
7ff6306c7000-7ff6306ca000 ---p 00000000 00:00 0                          [page size compat]
7ff6306ca000-7ff6306cb000 r--p 00008000 fe:09 1912                       /system/lib64/bootstrap/libdl.so

===== Smaps =====

7ff6306c2000-7ff6306c3000 r--p 00000000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          4 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            4 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd mr mw me ??
7ff6306c3000-7ff6306c6000 ---p 00000000 00:00 0                          [page size compat]
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: mr mw me
7ff6306c6000-7ff6306c7000 r-xp 00004000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          4 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            4 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd ex mr mw me ??
7ff6306c7000-7ff6306ca000 ---p 00000000 00:00 0                          [page size compat]
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: mr mw me
7ff6306ca000-7ff6306cb000 r--p 00008000 fe:09 1912                       /system/lib64/bootstrap/libdl.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   4 kB
Pss_Dirty:             4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         4 kB
Referenced:            4 kB
Anonymous:             4 kB
KSM:                   0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
FilePmdMapped:         0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:           0
VmFlags: rd mr mw me ac

Bug: 383389169
Bug: 409239984
Change-Id: Ic54e89571276db62ffc01681e7ca8986bb1ca7c4
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
This commit is contained in:
Kalesh Singh
2025-04-09 22:52:18 -07:00
committed by Carlos Llamas
parent d378f3ab39
commit 307be4b887
3 changed files with 38 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
fs/proc/task_mmu.c
View File

@@ -344,7 +344,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
}
start = vma->vm_start;
end = vma->vm_end;
end = VMA_PAD_START(vma);
__fold_filemap_fixup_entry(&((struct proc_maps_private *)m->private)->iter, &end);
@@ -366,13 +366,12 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
static int show_map(struct seq_file *m, void *v)
{
struct vm_area_struct *pad_vma = get_pad_vma(v);
struct vm_area_struct *vma = get_data_vma(v);
struct vm_area_struct *vma = v;
if (vma_pages(vma))
show_map_vma(m, vma);
show_map_pad_vma(vma, pad_vma, m, show_map_vma, false);
show_map_pad_vma(vma, m, show_map_vma, false);
return 0;
}
@@ -1078,9 +1077,10 @@ static void smap_gather_stats(struct vm_area_struct *vma,
struct mem_size_stats *mss, unsigned long start)
{
const struct mm_walk_ops *ops = &smaps_walk_ops;
unsigned long end = VMA_PAD_START(vma);
/* Invalid start */
if (start >= vma->vm_end)
if (start >= end)
return;
if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
@@ -1097,7 +1097,15 @@ static void smap_gather_stats(struct vm_area_struct *vma,
unsigned long shmem_swapped = shmem_swap_usage(vma);
if (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
!(vma->vm_flags & VM_WRITE))) {
!(vma->vm_flags & VM_WRITE)) &&
/*
* Only if we don't have padding can we use the fast path
* shmem_inode_info->swapped for shmem_swapped.
*
* Else we'll walk the page table to calculate
* shmem_swapped, (excluding the padding region).
*/
end == vma->vm_end) {
mss->swap += shmem_swapped;
} else {
ops = &smaps_shmem_walk_ops;
@@ -1106,9 +1114,9 @@ static void smap_gather_stats(struct vm_area_struct *vma,
/* mmap_lock is held in m_start */
if (!start)
walk_page_vma(vma, ops, mss);
walk_page_range(vma->vm_mm, vma->vm_start, end, ops, mss);
else
walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss);
walk_page_range(vma->vm_mm, start, end, ops, mss);
}
#define SEQ_PUT_DEC(str, val) \
@@ -1159,8 +1167,7 @@ static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss,
static int show_smap(struct seq_file *m, void *v)
{
struct vm_area_struct *pad_vma = get_pad_vma(v);
struct vm_area_struct *vma = get_data_vma(v);
struct vm_area_struct *vma = v;
struct mem_size_stats mss = {};
if (!vma_pages(vma))
@@ -1170,7 +1177,7 @@ static int show_smap(struct seq_file *m, void *v)
show_map_vma(m, vma);
SEQ_PUT_DEC("Size: ", vma->vm_end - vma->vm_start);
SEQ_PUT_DEC("Size: ", VMA_PAD_START(vma) - vma->vm_start);
SEQ_PUT_DEC(" kB\nKernelPageSize: ", vma_kernel_pagesize(vma));
SEQ_PUT_DEC(" kB\nMMUPageSize: ", vma_mmu_pagesize(vma));
seq_puts(m, " kB\n");
@@ -1186,7 +1193,7 @@ static int show_smap(struct seq_file *m, void *v)
show_smap_vma_flags(m, vma);
show_pad:
show_map_pad_vma(vma, pad_vma, m, show_smap, true);
show_map_pad_vma(vma, m, show_smap, true);
return 0;
}

16
include/linux/pgsize_migration.h
View File

@@ -26,12 +26,7 @@ extern unsigned long vma_pad_pages(struct vm_area_struct *vma);
extern void madvise_vma_pad_pages(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
extern struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma);
extern struct vm_area_struct *get_data_vma(struct vm_area_struct *vma);
extern void show_map_pad_vma(struct vm_area_struct *vma,
struct vm_area_struct *pad,
struct seq_file *m, void *func, bool smaps);
extern void split_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *new,
@@ -57,18 +52,7 @@ static inline void madvise_vma_pad_pages(struct vm_area_struct *vma,
{
}
static inline struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
{
return NULL;
}
static inline struct vm_area_struct *get_data_vma(struct vm_area_struct *vma)
{
return vma;
}
static inline void show_map_pad_vma(struct vm_area_struct *vma,
struct vm_area_struct *pad,
struct seq_file *m, void *func, bool smaps)
{
}

46
mm/pgsize_migration.c
View File

@@ -271,10 +271,10 @@ static const struct vm_operations_struct pad_vma_ops = {
};
/*
* Returns a new VMA representing the padding in @vma, if no padding
* in @vma returns NULL.
* Returns a new VMA representing the padding in @vma;
* returns NULL if no padding in @vma or allocation failed.
*/
struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
static struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
{
struct vm_area_struct *pad;
@@ -282,6 +282,10 @@ struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
return NULL;
pad = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
if (!pad) {
pr_warn("Page size migration: Failed to allocate padding VMA");
return NULL;
}
memcpy(pad, vma, sizeof(struct vm_area_struct));
@@ -306,34 +310,14 @@ struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
return pad;
}
/*
* Returns a new VMA exclusing the padding from @vma; if no padding in
* @vma returns @vma.
*/
struct vm_area_struct *get_data_vma(struct vm_area_struct *vma)
{
struct vm_area_struct *data;
if (!is_pgsize_migration_enabled() || !(vma->vm_flags & VM_PAD_MASK))
return vma;
data = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
memcpy(data, vma, sizeof(struct vm_area_struct));
/* Adjust the end to the start of the padding section */
data->vm_end = VMA_PAD_START(data);
return data;
}
/*
* Calls the show_pad_vma_fn on the @pad VMA, and frees the copies of @vma
* and @pad.
*/
void show_map_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *pad,
struct seq_file *m, void *func, bool smaps)
void show_map_pad_vma(struct vm_area_struct *vma, struct seq_file *m,
void *func, bool smaps)
{
struct vm_area_struct *pad = get_pad_vma(vma);
if (!pad)
return;
@@ -349,13 +333,21 @@ void show_map_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *pad,
*/
BUG_ON(!vma);
/* The pad VMA should be anonymous. */
BUG_ON(pad->vm_file);
/* The pad VMA should be PROT_NONE. */
BUG_ON(pad->vm_flags & (VM_READ|VM_WRITE|VM_EXEC));
/* The pad VMA itself cannot have padding; infinite recursion */
BUG_ON(pad->vm_flags & VM_PAD_MASK);
if (smaps)
((show_pad_smaps_fn)func)(m, pad);
else
((show_pad_maps_fn)func)(m, pad);
kfree(pad);
kfree(vma);
}
/*