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ANDROID: 16K: Separate padding from ELF LOAD segment mappings

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In has been found that some in-field apps depend on the output of
/proc/*/maps to determine the address ranges of other operations.

With the extension of LOAD segments VMAs to be contiguous in memory,
the apps may perform operations on an area that is not backed by the
underlying file, which results in a SIGBUS. Other apps have crashed
with yet unindentified reasons.

To avoid breaking in-field apps, maintain the output of /proc/*/[s]maps
with PROT_NONE VMAs for the padding pages of LOAD segmetns instead of
showing the segment extensions.

NOTE: This does not allocate actual backing VMAs for the shown
      PROT_NONE mappings.

This approach maintains 2 possible assumptions that userspace (apps)
could be depending on:
   1) That LOAD segment mappings are "contiguous" (not speparated by
      unrelated mappings) in memory.
   2) That no virtual address space is available between mappings of
      consecutive LOAD segments for the same ELF.

For example the output of /proc/*/[s]maps before and after this change
is shown below. Segments maintain PROT_NONE gaps ("[page size compat]")
for app compatiblity but these are not backed by actual slab VMA memory.

Maps Before:

7fb03604d000-7fb036051000 r--p 00000000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fb036051000-7fb036055000 r-xp 00004000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fb036055000-7fb036059000 r--p 00008000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fb036059000-7fb03605a000 rw-p 0000c000 fe:09 21935719                   /system/lib64/libnetd_client.so

Maps After:

7fc707390000-7fc707393000 r--p 00000000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fc707393000-7fc707394000 ---p 00000000 00:00 0                          [page size compat]
7fc707394000-7fc707398000 r-xp 00004000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fc707398000-7fc707399000 r--p 00008000 fe:09 21935719                   /system/lib64/libnetd_client.so
7fc707399000-7fc70739c000 ---p 00000000 00:00 0                          [page size compat]
7fc70739c000-7fc70739d000 rw-p 0000c000 fe:09 21935719                   /system/lib64/libnetd_client.so

Smaps Before:

7fb03604d000-7fb036051000 r--p 00000000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                 16 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                  16 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:         16 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:           16 kB
Anonymous:             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
7fb036051000-7fb036055000 r-xp 00004000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                 16 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                  16 kB
Pss:                   0 kB
Pss_Dirty:             0 kB
Shared_Clean:         16 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:           16 kB
Anonymous:             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
7fb036055000-7fb036059000 r--p 00008000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                 16 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
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
7fb036059000-7fb03605a000 rw-p 0000c000 fe:09 21935719                   /system/lib64/libnetd_client.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
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 wr mr mw me ac

Smaps After:

7fc707390000-7fc707393000 r--p 00000000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                  12 kB
Pss:                   0 kB
Shared_Clean:         12 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:           12 kB
Anonymous:             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 ??
7fc707393000-7fc707394000 ---p 00000000 00:00 0                          [page size compat]
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             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
7fc707394000-7fc707398000 r-xp 00004000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                 16 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                  16 kB
Pss:                   0 kB
Shared_Clean:         16 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:           16 kB
Anonymous:             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
7fc707398000-7fc707399000 r--p 00008000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         4 kB
Referenced:            4 kB
Anonymous:             4 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 ?? ??
7fc707399000-7fc70739c000 ---p 00000000 00:00 0                          [page size compat]
Size:                 12 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             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 ac
7fc70739c000-7fc70739d000 rw-p 0000c000 fe:09 21935719                   /system/lib64/libnetd_client.so
Size:                  4 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   4 kB
Pss:                   4 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         4 kB
Referenced:            4 kB
Anonymous:             4 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 wr mr mw me ac

Bug: 330117029
Bug: 327600007
Bug: 330767927
Bug: 328266487
Bug: 329803029
Change-Id: I12bf2c106fafc74a500d79155b81dde5db42661e
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
This commit is contained in:
Kalesh Singh 2024-04-04 23:02:30 -07:00
parent abbc0d53ee
commit ebf0750ad2
3 changed files with 133 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
fs/proc/task_mmu.c
View File

@ -9,6 +9,7 @@
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/pgsize_migration.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
#include <linux/swap.h>
@ -390,7 +391,13 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
static int show_map(struct seq_file *m, void *v)
{
show_map_vma(m, v);
struct vm_area_struct *pad_vma = get_pad_vma(v);
struct vm_area_struct *vma = get_data_vma(v);
show_map_vma(m, vma);
show_map_pad_vma(vma, pad_vma, m, show_map_vma);
return 0;
}
@ -887,7 +894,8 @@ 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 *vma = v;
struct vm_area_struct *pad_vma = get_pad_vma(v);
struct vm_area_struct *vma = get_data_vma(v);
struct mem_size_stats mss;
memset(&mss, 0, sizeof(mss));
@ -915,6 +923,8 @@ static int show_smap(struct seq_file *m, void *v)
seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma));
show_smap_vma_flags(m, vma);
show_map_pad_vma(vma, pad_vma, m, (show_pad_vma_fn)show_smap);
return 0;
}

29
include/linux/pgsize_migration.h
View File

@ -14,6 +14,7 @@
*/
#include <linux/mm.h>
#include <linux/seq_file.h>
#include <linux/sizes.h>
/*
@ -39,6 +40,10 @@
#define VM_PAD_WIDTH 4
#define VM_PAD_SHIFT (BITS_PER_LONG - VM_PAD_WIDTH)
#define VM_TOTAL_PAD_PAGES ((1ULL << VM_PAD_WIDTH) - 1)
#define VM_PAD_MASK (VM_TOTAL_PAD_PAGES << VM_PAD_SHIFT)
#define VMA_PAD_START(vma) (vma->vm_end - (vma_pad_pages(vma) << PAGE_SHIFT))
typedef void (*show_pad_vma_fn)(struct seq_file *m, struct vm_area_struct *vma);
#if PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT)
extern void vma_set_pad_pages(struct vm_area_struct *vma,
@ -48,6 +53,14 @@ 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, show_pad_vma_fn func);
#else /* PAGE_SIZE != SZ_4K || !defined(CONFIG_64BIT) */
static inline void vma_set_pad_pages(struct vm_area_struct *vma,
unsigned long nr_pages)
@ -63,6 +76,22 @@ static inline void madvise_vma_pad_pages(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
}
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, show_pad_vma_fn func)
{
}
#endif /* PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT) */
static inline unsigned long vma_data_pages(struct vm_area_struct *vma)

92
mm/pgsize_migration.c
View File

@ -16,6 +16,7 @@
#include <linux/jump_label.h>
#include <linux/kobject.h>
#include <linux/kstrtox.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#ifdef CONFIG_64BIT
@ -177,5 +178,96 @@ void madvise_vma_pad_pages(struct vm_area_struct *vma,
vma_set_pad_pages(vma, nr_pad_pages);
}
static const char *pad_vma_name(struct vm_area_struct *vma)
{
return "[page size compat]";
}
static const struct vm_operations_struct pad_vma_ops = {
.name = pad_vma_name,
};
/*
* Returns a new VMA representing the padding in @vma, if no padding
* in @vma returns NULL.
*/
struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
{
struct vm_area_struct *pad;
if (!is_pgsize_migration_enabled() || !(vma->vm_flags & VM_PAD_MASK))
return NULL;
pad = kzalloc(sizeof(struct vm_area_struct), GFP_KERNEL);
*pad = *vma;
/* Remove file */
pad->vm_file = NULL;
/* Add vm_ops->name */
pad->vm_ops = &pad_vma_ops;
/* Adjust the start to begin at the start of the padding section */
pad->vm_start = VMA_PAD_START(pad);
/* Make the pad vma PROT_NONE */
pad->vm_flags = pad->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
/* Remove padding bits */
pad->vm_flags = pad->vm_flags & ~VM_PAD_MASK;
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);
*data = *vma;
/* 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, show_pad_vma_fn func)
{
if (!pad)
return;
/*
* This cannot happen. If @pad vma was allocated the corresponding
* @vma should have the VM_PAD_MASK bit(s) set.
*/
BUG_ON(!(vma->vm_flags & VM_PAD_MASK));
/*
* This cannot happen. @pad is a section of the original VMA.
* Therefore @vma cannot be null if @pad is not null.
*/
BUG_ON(!vma);
func(m, pad);
kfree(pad);
kfree(vma);
}
#endif /* PAGE_SIZE == SZ_4K */
#endif /* CONFIG_64BIT */