From: Björn Töpel <bjorn(a)rivosinc.com>
BPF tests that load /proc/kallsyms, e.g. bpf_cookie, will perform a
buffer overrun if the number of syms on the system is larger than
MAX_SYMS.
Bump the MAX_SYMS to 400000, and add a runtime check that bails out if
the maximum is reached.
Signed-off-by: Björn Töpel <bjorn(a)rivosinc.com>
---
tools/testing/selftests/bpf/trace_helpers.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index 9b070cdf44ac..f83d9f65c65b 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -18,7 +18,7 @@
#define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe"
#define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
-#define MAX_SYMS 300000
+#define MAX_SYMS 400000
static struct ksym syms[MAX_SYMS];
static int sym_cnt;
@@ -46,6 +46,9 @@ int load_kallsyms_refresh(void)
break;
if (!addr)
continue;
+ if (i >= MAX_SYMS)
+ return -EFBIG;
+
syms[i].addr = (long) addr;
syms[i].name = strdup(func);
i++;
base-commit: fd283ab196a867f8f65f36913e0fadd031fcb823
--
2.39.2
*Changes in v23*:
- Set vec_buf_index in loop only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity
*Changes in v22*:
- Interface change:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
*Changes in v21*:
- Abort walk instead of returning error if WP is to be performed on
partial hugetlb
*Changes in v20*
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
*Changes in v19*
- Minor changes and interface updates
*Changes in v18*
- Rebase on top of next-20230613
- Minor updates
*Changes in v17*
- Rebase on top of next-20230606
- Minor improvements in PAGEMAP_SCAN IOCTL patch
*Changes in v16*
- Fix a corner case
- Add exclusive PM_SCAN_OP_WP back
*Changes in v15*
- Build fix (Add missed build fix in RESEND)
*Changes in v14*
- Fix build error caused by #ifdef added at last minute in some configs
*Changes in v13*
- Rebase on top of next-20230414
- Give-up on using uffd_wp_range() and write new helpers, flush tlb only
once
*Changes in v12*
- Update and other memory types to UFFD_FEATURE_WP_ASYNC
- Rebaase on top of next-20230406
- Review updates
*Changes in v11*
- Rebase on top of next-20230307
- Base patches on UFFD_FEATURE_WP_UNPOPULATED
- Do a lot of cosmetic changes and review updates
- Remove ENGAGE_WP + !GET operation as it can be performed with
UFFDIO_WRITEPROTECT
*Changes in v10*
- Add specific condition to return error if hugetlb is used with wp
async
- Move changes in tools/include/uapi/linux/fs.h to separate patch
- Add documentation
*Changes in v9:*
- Correct fault resolution for userfaultfd wp async
- Fix build warnings and errors which were happening on some configs
- Simplify pagemap ioctl's code
*Changes in v8:*
- Update uffd async wp implementation
- Improve PAGEMAP_IOCTL implementation
*Changes in v7:*
- Add uffd wp async
- Update the IOCTL to use uffd under the hood instead of soft-dirty
flags
*Motivation*
The real motivation for adding PAGEMAP_SCAN IOCTL is to emulate Windows
GetWriteWatch() syscall [1]. The GetWriteWatch{} retrieves the addresses of
the pages that are written to in a region of virtual memory.
This syscall is used in Windows applications and games etc. This syscall is
being emulated in pretty slow manner in userspace. Our purpose is to
enhance the kernel such that we translate it efficiently in a better way.
Currently some out of tree hack patches are being used to efficiently
emulate it in some kernels. We intend to replace those with these patches.
So the whole gaming on Linux can effectively get benefit from this. It
means there would be tons of users of this code.
CRIU use case [2] was mentioned by Andrei and Danylo:
> Use cases for migrating sparse VMAs are binaries sanitized with ASAN,
> MSAN or TSAN [3]. All of these sanitizers produce sparse mappings of
> shadow memory [4]. Being able to migrate such binaries allows to highly
> reduce the amount of work needed to identify and fix post-migration
> crashes, which happen constantly.
Andrei's defines the following uses of this code:
* it is more granular and allows us to track changed pages more
effectively. The current interface can clear dirty bits for the entire
process only. In addition, reading info about pages is a separate
operation. It means we must freeze the process to read information
about all its pages, reset dirty bits, only then we can start dumping
pages. The information about pages becomes more and more outdated,
while we are processing pages. The new interface solves both these
downsides. First, it allows us to read pte bits and clear the
soft-dirty bit atomically. It means that CRIU will not need to freeze
processes to pre-dump their memory. Second, it clears soft-dirty bits
for a specified region of memory. It means CRIU will have actual info
about pages to the moment of dumping them.
* The new interface has to be much faster because basic page filtering
is happening in the kernel. With the old interface, we have to read
pagemap for each page.
*Implementation Evolution (Short Summary)*
From the definition of GetWriteWatch(), we feel like kernel's soft-dirty
feature can be used under the hood with some additions like:
* reset soft-dirty flag for only a specific region of memory instead of
clearing the flag for the entire process
* get and clear soft-dirty flag for a specific region atomically
So we decided to use ioctl on pagemap file to read or/and reset soft-dirty
flag. But using soft-dirty flag, sometimes we get extra pages which weren't
even written. They had become soft-dirty because of VMA merging and
VM_SOFTDIRTY flag. This breaks the definition of GetWriteWatch(). We were
able to by-pass this short coming by ignoring VM_SOFTDIRTY until David
reported that mprotect etc messes up the soft-dirty flag while ignoring
VM_SOFTDIRTY [5]. This wasn't happening until [6] got introduced. We
discussed if we can revert these patches. But we could not reach to any
conclusion. So at this point, I made couple of tries to solve this whole
VM_SOFTDIRTY issue by correcting the soft-dirty implementation:
* [7] Correct the bug fixed wrongly back in 2014. It had potential to cause
regression. We left it behind.
* [8] Keep a list of soft-dirty part of a VMA across splits and merges. I
got the reply don't increase the size of the VMA by 8 bytes.
At this point, we left soft-dirty considering it is too much delicate and
userfaultfd [9] seemed like the only way forward. From there onward, we
have been basing soft-dirty emulation on userfaultfd wp feature where
kernel resolves the faults itself when WP_ASYNC feature is used. It was
straight forward to add WP_ASYNC feature in userfautlfd. Now we get only
those pages dirty or written-to which are really written in reality. (PS
There is another WP_UNPOPULATED userfautfd feature is required which is
needed to avoid pre-faulting memory before write-protecting [9].)
All the different masks were added on the request of CRIU devs to create
interface more generic and better.
[1] https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-…
[2] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com
[3] https://github.com/google/sanitizers
[4] https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit
[5] https://lore.kernel.org/all/bfcae708-db21-04b4-0bbe-712badd03071@redhat.com
[6] https://lore.kernel.org/all/20220725142048.30450-1-peterx@redhat.com/
[7] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.…
[8] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.…
[9] https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com
[10] https://lore.kernel.org/all/20230125144529.1630917-1-mdanylo@google.com
* Original Cover letter from v8*
Hello,
Note:
Soft-dirty pages and pages which have been written-to are synonyms. As
kernel already has soft-dirty feature inside which we have given up to
use, we are using written-to terminology while using UFFD async WP under
the hood.
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear
the info about page table entries. The following operations are
supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN),
file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped
(PAGE_IS_SWAPPED).
- Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which
pages have been written-to.
- Find pages which have been written-to and write protect the pages
(atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
It is possible to find and clear soft-dirty pages entirely in userspace.
But it isn't efficient:
- The mprotect and SIGSEGV handler for bookkeeping
- The userfaultfd wp (synchronous) with the handler for bookkeeping
Some benchmarks can be seen here[1]. This series adds features that weren't
present earlier:
- There is no atomic get soft-dirty/Written-to status and clear present in
the kernel.
- The pages which have been written-to can not be found in accurate way.
(Kernel's soft-dirty PTE bit + sof_dirty VMA bit shows more soft-dirty
pages than there actually are.)
Historically, soft-dirty PTE bit tracking has been used in the CRIU
project. The procfs interface is enough for finding the soft-dirty bit
status and clearing the soft-dirty bit of all the pages of a process.
We have the use case where we need to track the soft-dirty PTE bit for
only specific pages on-demand. We need this tracking and clear mechanism
of a region of memory while the process is running to emulate the
getWriteWatch() syscall of Windows.
*(Moved to using UFFD instead of soft-dirtyi feature to find pages which
have been written-to from v7 patch series)*:
Stop using the soft-dirty flags for finding which pages have been
written to. It is too delicate and wrong as it shows more soft-dirty
pages than the actual soft-dirty pages. There is no interest in
correcting it [2][3] as this is how the feature was written years ago.
It shouldn't be updated to changed behaviour. Peter Xu has suggested
using the async version of the UFFD WP [4] as it is based inherently
on the PTEs.
So in this patch series, I've added a new mode to the UFFD which is
asynchronous version of the write protect. When this variant of the
UFFD WP is used, the page faults are resolved automatically by the
kernel. The pages which have been written-to can be found by reading
pagemap file (!PM_UFFD_WP). This feature can be used successfully to
find which pages have been written to from the time the pages were
write protected. This works just like the soft-dirty flag without
showing any extra pages which aren't soft-dirty in reality.
The information related to pages if the page is file mapped, present and
swapped is required for the CRIU project [5][6]. The addition of the
required mask, any mask, excluded mask and return masks are also required
for the CRIU project [5].
The IOCTL returns the addresses of the pages which match the specific
masks. The page addresses are returned in struct page_region in a compact
form. The max_pages is needed to support a use case where user only wants
to get a specific number of pages. So there is no need to find all the
pages of interest in the range when max_pages is specified. The IOCTL
returns when the maximum number of the pages are found. The max_pages is
optional. If max_pages is specified, it must be equal or greater than the
vec_size. This restriction is needed to handle worse case when one
page_region only contains info of one page and it cannot be compacted.
This is needed to emulate the Windows getWriteWatch() syscall.
The patch series include the detailed selftest which can be used as an
example for the uffd async wp test and PAGEMAP_IOCTL. It shows the
interface usages as well.
[1] https://lore.kernel.org/lkml/54d4c322-cd6e-eefd-b161-2af2b56aae24@collabora…
[2] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.…
[3] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.…
[4] https://lore.kernel.org/all/Y6Hc2d+7eTKs7AiH@x1n
[5] https://lore.kernel.org/all/YyiDg79flhWoMDZB@gmail.com/
[6] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com/
Regards,
Muhammad Usama Anjum
Muhammad Usama Anjum (4):
fs/proc/task_mmu: Implement IOCTL to get and optionally clear info
about PTEs
tools headers UAPI: Update linux/fs.h with the kernel sources
mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL
selftests: mm: add pagemap ioctl tests
Peter Xu (1):
userfaultfd: UFFD_FEATURE_WP_ASYNC
Documentation/admin-guide/mm/pagemap.rst | 58 +
Documentation/admin-guide/mm/userfaultfd.rst | 35 +
fs/proc/task_mmu.c | 577 +++++++
fs/userfaultfd.c | 26 +-
include/linux/hugetlb.h | 1 +
include/linux/userfaultfd_k.h | 21 +-
include/uapi/linux/fs.h | 55 +
include/uapi/linux/userfaultfd.h | 9 +-
mm/hugetlb.c | 34 +-
mm/memory.c | 27 +-
tools/include/uapi/linux/fs.h | 55 +
tools/testing/selftests/mm/.gitignore | 2 +
tools/testing/selftests/mm/Makefile | 3 +-
tools/testing/selftests/mm/config | 1 +
tools/testing/selftests/mm/pagemap_ioctl.c | 1464 ++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 4 +
16 files changed, 2348 insertions(+), 24 deletions(-)
create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c
mode change 100644 => 100755 tools/testing/selftests/mm/run_vmtests.sh
--
2.39.2
Changes in v22:
- Interface change:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
Changes in v21:
- Abort walk instead of returning error if WP is to be performed on
partial hugetlb
*Changes in v20*
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
*Changes in v19*
- Minor changes and interface updates
*Changes in v18*
- Rebase on top of next-20230613
- Minor updates
*Changes in v17*
- Rebase on top of next-20230606
- Minor improvements in PAGEMAP_SCAN IOCTL patch
*Changes in v16*
- Fix a corner case
- Add exclusive PM_SCAN_OP_WP back
*Changes in v15*
- Build fix (Add missed build fix in RESEND)
*Changes in v14*
- Fix build error caused by #ifdef added at last minute in some configs
*Changes in v13*
- Rebase on top of next-20230414
- Give-up on using uffd_wp_range() and write new helpers, flush tlb only
once
*Changes in v12*
- Update and other memory types to UFFD_FEATURE_WP_ASYNC
- Rebaase on top of next-20230406
- Review updates
*Changes in v11*
- Rebase on top of next-20230307
- Base patches on UFFD_FEATURE_WP_UNPOPULATED
- Do a lot of cosmetic changes and review updates
- Remove ENGAGE_WP + !GET operation as it can be performed with
UFFDIO_WRITEPROTECT
*Changes in v10*
- Add specific condition to return error if hugetlb is used with wp
async
- Move changes in tools/include/uapi/linux/fs.h to separate patch
- Add documentation
*Changes in v9:*
- Correct fault resolution for userfaultfd wp async
- Fix build warnings and errors which were happening on some configs
- Simplify pagemap ioctl's code
*Changes in v8:*
- Update uffd async wp implementation
- Improve PAGEMAP_IOCTL implementation
*Changes in v7:*
- Add uffd wp async
- Update the IOCTL to use uffd under the hood instead of soft-dirty
flags
*Motivation*
The real motivation for adding PAGEMAP_SCAN IOCTL is to emulate Windows
GetWriteWatch() syscall [1]. The GetWriteWatch{} retrieves the addresses of
the pages that are written to in a region of virtual memory.
This syscall is used in Windows applications and games etc. This syscall is
being emulated in pretty slow manner in userspace. Our purpose is to
enhance the kernel such that we translate it efficiently in a better way.
Currently some out of tree hack patches are being used to efficiently
emulate it in some kernels. We intend to replace those with these patches.
So the whole gaming on Linux can effectively get benefit from this. It
means there would be tons of users of this code.
CRIU use case [2] was mentioned by Andrei and Danylo:
> Use cases for migrating sparse VMAs are binaries sanitized with ASAN,
> MSAN or TSAN [3]. All of these sanitizers produce sparse mappings of
> shadow memory [4]. Being able to migrate such binaries allows to highly
> reduce the amount of work needed to identify and fix post-migration
> crashes, which happen constantly.
Andrei's defines the following uses of this code:
* it is more granular and allows us to track changed pages more
effectively. The current interface can clear dirty bits for the entire
process only. In addition, reading info about pages is a separate
operation. It means we must freeze the process to read information
about all its pages, reset dirty bits, only then we can start dumping
pages. The information about pages becomes more and more outdated,
while we are processing pages. The new interface solves both these
downsides. First, it allows us to read pte bits and clear the
soft-dirty bit atomically. It means that CRIU will not need to freeze
processes to pre-dump their memory. Second, it clears soft-dirty bits
for a specified region of memory. It means CRIU will have actual info
about pages to the moment of dumping them.
* The new interface has to be much faster because basic page filtering
is happening in the kernel. With the old interface, we have to read
pagemap for each page.
*Implementation Evolution (Short Summary)*
From the definition of GetWriteWatch(), we feel like kernel's soft-dirty
feature can be used under the hood with some additions like:
* reset soft-dirty flag for only a specific region of memory instead of
clearing the flag for the entire process
* get and clear soft-dirty flag for a specific region atomically
So we decided to use ioctl on pagemap file to read or/and reset soft-dirty
flag. But using soft-dirty flag, sometimes we get extra pages which weren't
even written. They had become soft-dirty because of VMA merging and
VM_SOFTDIRTY flag. This breaks the definition of GetWriteWatch(). We were
able to by-pass this short coming by ignoring VM_SOFTDIRTY until David
reported that mprotect etc messes up the soft-dirty flag while ignoring
VM_SOFTDIRTY [5]. This wasn't happening until [6] got introduced. We
discussed if we can revert these patches. But we could not reach to any
conclusion. So at this point, I made couple of tries to solve this whole
VM_SOFTDIRTY issue by correcting the soft-dirty implementation:
* [7] Correct the bug fixed wrongly back in 2014. It had potential to cause
regression. We left it behind.
* [8] Keep a list of soft-dirty part of a VMA across splits and merges. I
got the reply don't increase the size of the VMA by 8 bytes.
At this point, we left soft-dirty considering it is too much delicate and
userfaultfd [9] seemed like the only way forward. From there onward, we
have been basing soft-dirty emulation on userfaultfd wp feature where
kernel resolves the faults itself when WP_ASYNC feature is used. It was
straight forward to add WP_ASYNC feature in userfautlfd. Now we get only
those pages dirty or written-to which are really written in reality. (PS
There is another WP_UNPOPULATED userfautfd feature is required which is
needed to avoid pre-faulting memory before write-protecting [9].)
All the different masks were added on the request of CRIU devs to create
interface more generic and better.
[1] https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-…
[2] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com
[3] https://github.com/google/sanitizers
[4] https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit
[5] https://lore.kernel.org/all/bfcae708-db21-04b4-0bbe-712badd03071@redhat.com
[6] https://lore.kernel.org/all/20220725142048.30450-1-peterx@redhat.com/
[7] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.…
[8] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.…
[9] https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com
[10] https://lore.kernel.org/all/20230125144529.1630917-1-mdanylo@google.com
* Original Cover letter from v8*
Hello,
Note:
Soft-dirty pages and pages which have been written-to are synonyms. As
kernel already has soft-dirty feature inside which we have given up to
use, we are using written-to terminology while using UFFD async WP under
the hood.
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear
the info about page table entries. The following operations are
supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN),
file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped
(PAGE_IS_SWAPPED).
- Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which
pages have been written-to.
- Find pages which have been written-to and write protect the pages
(atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
It is possible to find and clear soft-dirty pages entirely in userspace.
But it isn't efficient:
- The mprotect and SIGSEGV handler for bookkeeping
- The userfaultfd wp (synchronous) with the handler for bookkeeping
Some benchmarks can be seen here[1]. This series adds features that weren't
present earlier:
- There is no atomic get soft-dirty/Written-to status and clear present in
the kernel.
- The pages which have been written-to can not be found in accurate way.
(Kernel's soft-dirty PTE bit + sof_dirty VMA bit shows more soft-dirty
pages than there actually are.)
Historically, soft-dirty PTE bit tracking has been used in the CRIU
project. The procfs interface is enough for finding the soft-dirty bit
status and clearing the soft-dirty bit of all the pages of a process.
We have the use case where we need to track the soft-dirty PTE bit for
only specific pages on-demand. We need this tracking and clear mechanism
of a region of memory while the process is running to emulate the
getWriteWatch() syscall of Windows.
*(Moved to using UFFD instead of soft-dirtyi feature to find pages which
have been written-to from v7 patch series)*:
Stop using the soft-dirty flags for finding which pages have been
written to. It is too delicate and wrong as it shows more soft-dirty
pages than the actual soft-dirty pages. There is no interest in
correcting it [2][3] as this is how the feature was written years ago.
It shouldn't be updated to changed behaviour. Peter Xu has suggested
using the async version of the UFFD WP [4] as it is based inherently
on the PTEs.
So in this patch series, I've added a new mode to the UFFD which is
asynchronous version of the write protect. When this variant of the
UFFD WP is used, the page faults are resolved automatically by the
kernel. The pages which have been written-to can be found by reading
pagemap file (!PM_UFFD_WP). This feature can be used successfully to
find which pages have been written to from the time the pages were
write protected. This works just like the soft-dirty flag without
showing any extra pages which aren't soft-dirty in reality.
The information related to pages if the page is file mapped, present and
swapped is required for the CRIU project [5][6]. The addition of the
required mask, any mask, excluded mask and return masks are also required
for the CRIU project [5].
The IOCTL returns the addresses of the pages which match the specific
masks. The page addresses are returned in struct page_region in a compact
form. The max_pages is needed to support a use case where user only wants
to get a specific number of pages. So there is no need to find all the
pages of interest in the range when max_pages is specified. The IOCTL
returns when the maximum number of the pages are found. The max_pages is
optional. If max_pages is specified, it must be equal or greater than the
vec_size. This restriction is needed to handle worse case when one
page_region only contains info of one page and it cannot be compacted.
This is needed to emulate the Windows getWriteWatch() syscall.
The patch series include the detailed selftest which can be used as an
example for the uffd async wp test and PAGEMAP_IOCTL. It shows the
interface usages as well.
[1] https://lore.kernel.org/lkml/54d4c322-cd6e-eefd-b161-2af2b56aae24@collabora…
[2] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.…
[3] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.…
[4] https://lore.kernel.org/all/Y6Hc2d+7eTKs7AiH@x1n
[5] https://lore.kernel.org/all/YyiDg79flhWoMDZB@gmail.com/
[6] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com/
Regards,
Muhammad Usama Anjum
Muhammad Usama Anjum (4):
fs/proc/task_mmu: Implement IOCTL to get and optionally clear info
about PTEs
tools headers UAPI: Update linux/fs.h with the kernel sources
mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL
selftests: mm: add pagemap ioctl tests
Peter Xu (1):
userfaultfd: UFFD_FEATURE_WP_ASYNC
Documentation/admin-guide/mm/pagemap.rst | 58 +
Documentation/admin-guide/mm/userfaultfd.rst | 35 +
fs/proc/task_mmu.c | 565 +++++++
fs/userfaultfd.c | 26 +-
include/linux/hugetlb.h | 1 +
include/linux/userfaultfd_k.h | 21 +-
include/uapi/linux/fs.h | 55 +
include/uapi/linux/userfaultfd.h | 9 +-
mm/hugetlb.c | 34 +-
mm/memory.c | 27 +-
tools/include/uapi/linux/fs.h | 55 +
tools/testing/selftests/mm/.gitignore | 2 +
tools/testing/selftests/mm/Makefile | 3 +-
tools/testing/selftests/mm/config | 1 +
tools/testing/selftests/mm/pagemap_ioctl.c | 1464 ++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 4 +
16 files changed, 2336 insertions(+), 24 deletions(-)
create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c
mode change 100644 => 100755 tools/testing/selftests/mm/run_vmtests.sh
--
2.39.2
The basic idea here is to "simulate" memory poisoning for VMs. A VM
running on some host might encounter a memory error, after which some
page(s) are poisoned (i.e., future accesses SIGBUS). They expect that
once poisoned, pages can never become "un-poisoned". So, when we live
migrate the VM, we need to preserve the poisoned status of these pages.
When live migrating, we try to get the guest running on its new host as
quickly as possible. So, we start it running before all memory has been
copied, and before we're certain which pages should be poisoned or not.
So the basic way to use this new feature is:
- On the new host, the guest's memory is registered with userfaultfd, in
either MISSING or MINOR mode (doesn't really matter for this purpose).
- On any first access, we get a userfaultfd event. At this point we can
communicate with the old host to find out if the page was poisoned.
- If so, we can respond with a UFFDIO_POISON - this places a swap marker
so any future accesses will SIGBUS. Because the pte is now "present",
future accesses won't generate more userfaultfd events, they'll just
SIGBUS directly.
UFFDIO_POISON does not handle unmapping previously-present PTEs. This
isn't needed, because during live migration we want to intercept
all accesses with userfaultfd (not just writes, so WP mode isn't useful
for this). So whether minor or missing mode is being used (or both), the
PTE won't be present in any case, so handling that case isn't needed.
Why return VM_FAULT_HWPOISON instead of VM_FAULT_SIGBUS when one of
these markers is encountered? For "normal" userspace programs there
isn't a big difference, both yield a SIGBUS. The difference for KVM is
key though: VM_FAULT_HWPOISON will result in an MCE being injected into
the guest (which is the behavior we want). With VM_FAULT_SIGBUS, the
hypervisor would need to catch the SIGBUS and deal with the MCE
injection itself.
Signed-off-by: Axel Rasmussen <axelrasmussen(a)google.com>
---
fs/userfaultfd.c | 63 ++++++++++++++++++++++++++++++++
include/linux/swapops.h | 3 +-
include/linux/userfaultfd_k.h | 4 ++
include/uapi/linux/userfaultfd.h | 25 +++++++++++--
mm/memory.c | 4 ++
mm/userfaultfd.c | 62 ++++++++++++++++++++++++++++++-
6 files changed, 156 insertions(+), 5 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 7cecd49e078b..c26a883399c9 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1965,6 +1965,66 @@ static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg)
return ret;
}
+static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long arg)
+{
+ __s64 ret;
+ struct uffdio_poison uffdio_poison;
+ struct uffdio_poison __user *user_uffdio_poison;
+ struct userfaultfd_wake_range range;
+
+ user_uffdio_poison = (struct uffdio_poison __user *)arg;
+
+ ret = -EAGAIN;
+ if (atomic_read(&ctx->mmap_changing))
+ goto out;
+
+ ret = -EFAULT;
+ if (copy_from_user(&uffdio_poison, user_uffdio_poison,
+ /* don't copy the output fields */
+ sizeof(uffdio_poison) - (sizeof(__s64))))
+ goto out;
+
+ ret = validate_range(ctx->mm, uffdio_poison.range.start,
+ uffdio_poison.range.len);
+ if (ret)
+ goto out;
+
+ ret = -EINVAL;
+ /* double check for wraparound just in case. */
+ if (uffdio_poison.range.start + uffdio_poison.range.len <=
+ uffdio_poison.range.start) {
+ goto out;
+ }
+ if (uffdio_poison.mode & ~UFFDIO_POISON_MODE_DONTWAKE)
+ goto out;
+
+ if (mmget_not_zero(ctx->mm)) {
+ ret = mfill_atomic_poison(ctx->mm, uffdio_poison.range.start,
+ uffdio_poison.range.len,
+ &ctx->mmap_changing, 0);
+ mmput(ctx->mm);
+ } else {
+ return -ESRCH;
+ }
+
+ if (unlikely(put_user(ret, &user_uffdio_poison->updated)))
+ return -EFAULT;
+ if (ret < 0)
+ goto out;
+
+ /* len == 0 would wake all */
+ BUG_ON(!ret);
+ range.len = ret;
+ if (!(uffdio_poison.mode & UFFDIO_POISON_MODE_DONTWAKE)) {
+ range.start = uffdio_poison.range.start;
+ wake_userfault(ctx, &range);
+ }
+ ret = range.len == uffdio_poison.range.len ? 0 : -EAGAIN;
+
+out:
+ return ret;
+}
+
static inline unsigned int uffd_ctx_features(__u64 user_features)
{
/*
@@ -2066,6 +2126,9 @@ static long userfaultfd_ioctl(struct file *file, unsigned cmd,
case UFFDIO_CONTINUE:
ret = userfaultfd_continue(ctx, arg);
break;
+ case UFFDIO_POISON:
+ ret = userfaultfd_poison(ctx, arg);
+ break;
}
return ret;
}
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 4c932cb45e0b..8259fee32421 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -394,7 +394,8 @@ typedef unsigned long pte_marker;
#define PTE_MARKER_UFFD_WP BIT(0)
#define PTE_MARKER_SWAPIN_ERROR BIT(1)
-#define PTE_MARKER_MASK (BIT(2) - 1)
+#define PTE_MARKER_UFFD_POISON BIT(2)
+#define PTE_MARKER_MASK (BIT(3) - 1)
static inline swp_entry_t make_pte_marker_entry(pte_marker marker)
{
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index ac7b0c96d351..ac8c6854097c 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -46,6 +46,7 @@ enum mfill_atomic_mode {
MFILL_ATOMIC_COPY,
MFILL_ATOMIC_ZEROPAGE,
MFILL_ATOMIC_CONTINUE,
+ MFILL_ATOMIC_POISON,
NR_MFILL_ATOMIC_MODES,
};
@@ -83,6 +84,9 @@ extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm,
extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long dst_start,
unsigned long len, atomic_t *mmap_changing,
uffd_flags_t flags);
+extern ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start,
+ unsigned long len, atomic_t *mmap_changing,
+ uffd_flags_t flags);
extern int mwriteprotect_range(struct mm_struct *dst_mm,
unsigned long start, unsigned long len,
bool enable_wp, atomic_t *mmap_changing);
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 66dd4cd277bd..62151706c5a3 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -39,7 +39,8 @@
UFFD_FEATURE_MINOR_SHMEM | \
UFFD_FEATURE_EXACT_ADDRESS | \
UFFD_FEATURE_WP_HUGETLBFS_SHMEM | \
- UFFD_FEATURE_WP_UNPOPULATED)
+ UFFD_FEATURE_WP_UNPOPULATED | \
+ UFFD_FEATURE_POISON)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@@ -49,12 +50,14 @@
(__u64)1 << _UFFDIO_COPY | \
(__u64)1 << _UFFDIO_ZEROPAGE | \
(__u64)1 << _UFFDIO_WRITEPROTECT | \
- (__u64)1 << _UFFDIO_CONTINUE)
+ (__u64)1 << _UFFDIO_CONTINUE | \
+ (__u64)1 << _UFFDIO_POISON)
#define UFFD_API_RANGE_IOCTLS_BASIC \
((__u64)1 << _UFFDIO_WAKE | \
(__u64)1 << _UFFDIO_COPY | \
+ (__u64)1 << _UFFDIO_WRITEPROTECT | \
(__u64)1 << _UFFDIO_CONTINUE | \
- (__u64)1 << _UFFDIO_WRITEPROTECT)
+ (__u64)1 << _UFFDIO_POISON)
/*
* Valid ioctl command number range with this API is from 0x00 to
@@ -71,6 +74,7 @@
#define _UFFDIO_ZEROPAGE (0x04)
#define _UFFDIO_WRITEPROTECT (0x06)
#define _UFFDIO_CONTINUE (0x07)
+#define _UFFDIO_POISON (0x08)
#define _UFFDIO_API (0x3F)
/* userfaultfd ioctl ids */
@@ -91,6 +95,8 @@
struct uffdio_writeprotect)
#define UFFDIO_CONTINUE _IOWR(UFFDIO, _UFFDIO_CONTINUE, \
struct uffdio_continue)
+#define UFFDIO_POISON _IOWR(UFFDIO, _UFFDIO_POISON, \
+ struct uffdio_poison)
/* read() structure */
struct uffd_msg {
@@ -225,6 +231,7 @@ struct uffdio_api {
#define UFFD_FEATURE_EXACT_ADDRESS (1<<11)
#define UFFD_FEATURE_WP_HUGETLBFS_SHMEM (1<<12)
#define UFFD_FEATURE_WP_UNPOPULATED (1<<13)
+#define UFFD_FEATURE_POISON (1<<14)
__u64 features;
__u64 ioctls;
@@ -321,6 +328,18 @@ struct uffdio_continue {
__s64 mapped;
};
+struct uffdio_poison {
+ struct uffdio_range range;
+#define UFFDIO_POISON_MODE_DONTWAKE ((__u64)1<<0)
+ __u64 mode;
+
+ /*
+ * Fields below here are written by the ioctl and must be at the end:
+ * the copy_from_user will not read past here.
+ */
+ __s64 updated;
+};
+
/*
* Flags for the userfaultfd(2) system call itself.
*/
diff --git a/mm/memory.c b/mm/memory.c
index d8a9a770b1f1..7fbda39e060d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3692,6 +3692,10 @@ static vm_fault_t handle_pte_marker(struct vm_fault *vmf)
if (WARN_ON_ONCE(!marker))
return VM_FAULT_SIGBUS;
+ /* Poison emulation explicitly requested for this PTE. */
+ if (marker & PTE_MARKER_UFFD_POISON)
+ return VM_FAULT_HWPOISON;
+
/* Higher priority than uffd-wp when data corrupted */
if (marker & PTE_MARKER_SWAPIN_ERROR)
return VM_FAULT_SIGBUS;
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index a2bf37ee276d..87b62ca1e09e 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -286,6 +286,51 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
goto out;
}
+/* Handles UFFDIO_POISON for all non-hugetlb VMAs. */
+static int mfill_atomic_pte_poison(pmd_t *dst_pmd,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_addr,
+ uffd_flags_t flags)
+{
+ int ret;
+ struct mm_struct *dst_mm = dst_vma->vm_mm;
+ pte_t _dst_pte, *dst_pte;
+ spinlock_t *ptl;
+
+ _dst_pte = make_pte_marker(PTE_MARKER_UFFD_POISON);
+ dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+
+ if (vma_is_shmem(dst_vma)) {
+ struct inode *inode;
+ pgoff_t offset, max_off;
+
+ /* serialize against truncate with the page table lock */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_unlock;
+ }
+
+ ret = -EEXIST;
+ /*
+ * For now, we don't handle unmapping pages, so only support filling in
+ * none PTEs, or replacing PTE markers.
+ */
+ if (!pte_none_mostly(*dst_pte))
+ goto out_unlock;
+
+ set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+
+ /* No need to invalidate - it was non-present before */
+ update_mmu_cache(dst_vma, dst_addr, dst_pte);
+ ret = 0;
+out_unlock:
+ pte_unmap_unlock(dst_pte, ptl);
+ return ret;
+}
+
static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
{
pgd_t *pgd;
@@ -336,8 +381,12 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
* supported by hugetlb. A PMD_SIZE huge pages may exist as used
* by THP. Since we can not reliably insert a zero page, this
* feature is not supported.
+ *
+ * PTE marker handling for hugetlb is a bit special, so for now
+ * UFFDIO_POISON is not supported.
*/
- if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
+ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE) ||
+ uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
mmap_read_unlock(dst_mm);
return -EINVAL;
}
@@ -481,6 +530,9 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) {
return mfill_atomic_pte_continue(dst_pmd, dst_vma,
dst_addr, flags);
+ } else if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
+ return mfill_atomic_pte_poison(dst_pmd, dst_vma,
+ dst_addr, flags);
}
/*
@@ -702,6 +754,14 @@ ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start,
uffd_flags_set_mode(flags, MFILL_ATOMIC_CONTINUE));
}
+ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start,
+ unsigned long len, atomic_t *mmap_changing,
+ uffd_flags_t flags)
+{
+ return mfill_atomic(dst_mm, start, 0, len, mmap_changing,
+ uffd_flags_set_mode(flags, MFILL_ATOMIC_POISON));
+}
+
long uffd_wp_range(struct vm_area_struct *dst_vma,
unsigned long start, unsigned long len, bool enable_wp)
{
--
2.41.0.255.g8b1d071c50-goog
From: Björn Töpel <bjorn(a)rivosinc.com>
This series has two minor fixes, found when cross-compiling for the
RISC-V architecture.
Some RISC-V systems do not define HAVE_EFFICIENT_UNALIGNED_ACCESS,
which made some of tests bail out. Fix the failing tests by adding
F_NEEDS_EFFICIENT_UNALIGNED_ACCESS.
...and some RISC-V systems *do* define
HAVE_EFFICIENT_UNALIGNED_ACCESS. In this case the autoconf.h was not
correctly picked up by the build system.
Cheers,
Björn
Björn Töpel (2):
selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests
selftests/bpf: Honor $(O) when figuring out paths
tools/testing/selftests/bpf/Makefile | 4 ++++
tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c | 1 +
tools/testing/selftests/bpf/verifier/ctx_skb.c | 2 ++
tools/testing/selftests/bpf/verifier/jmp32.c | 8 ++++++++
tools/testing/selftests/bpf/verifier/map_kptr.c | 2 ++
tools/testing/selftests/bpf/verifier/precise.c | 2 +-
6 files changed, 18 insertions(+), 1 deletion(-)
base-commit: a94098d490e17d652770f2309fcb9b46bc4cf864
--
2.39.2
In use_missing_map function, value is
initialized twice.There is no
connection between the two assignment.
This patch could fix this bug.
Signed-off-by: Wang Ming <machel(a)vivo.com>
---
tools/testing/selftests/bpf/progs/test_log_fixup.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/test_log_fixup.c b/tools/testing/selftests/bpf/progs/test_log_fixup.c
index 1bd48feaaa42..1c49b2f9be6c 100644
--- a/tools/testing/selftests/bpf/progs/test_log_fixup.c
+++ b/tools/testing/selftests/bpf/progs/test_log_fixup.c
@@ -52,13 +52,9 @@ struct {
SEC("?raw_tp/sys_enter")
int use_missing_map(const void *ctx)
{
- int zero = 0, *value;
+ int zero = 0;
- value = bpf_map_lookup_elem(&existing_map, &zero);
-
- value = bpf_map_lookup_elem(&missing_map, &zero);
-
- return value != NULL;
+ return bpf_map_lookup_elem(&missing_map, &zero) != NULL;
}
extern int bpf_nonexistent_kfunc(void) __ksym __weak;
--
2.25.1
From: Björn Töpel <bjorn(a)rivosinc.com>
Timeouts in kselftest are done using the "timeout" command with the
"--foreground" option. Without the "foreground" option, it is not
possible for a user to cancel the runner using SIGINT, because the
signal is not propagated to timeout which is running in a different
process group. The "forground" options places the timeout in the same
process group as its parent, but only sends the SIGTERM (on timeout)
signal to the forked process. Unfortunately, this does not play nice
with all kselftests, e.g. "net:fcnal-test.sh", where the child
processes will linger because timeout does not send SIGTERM to the
group.
Some users have noted these hangs [1].
Fix this by nesting the timeout with an additional timeout without the
foreground option.
Link: https://lore.kernel.org/all/7650b2eb-0aee-a2b0-2e64-c9bc63210f67@alu.unizg.… # [1]
Fixes: 651e0d881461 ("kselftest/runner: allow to properly deliver signals to tests")
Signed-off-by: Björn Töpel <bjorn(a)rivosinc.com>
---
tools/testing/selftests/kselftest/runner.sh | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kselftest/runner.sh b/tools/testing/selftests/kselftest/runner.sh
index 1c952d1401d4..70e0a465e30d 100644
--- a/tools/testing/selftests/kselftest/runner.sh
+++ b/tools/testing/selftests/kselftest/runner.sh
@@ -36,7 +36,8 @@ tap_timeout()
{
# Make sure tests will time out if utility is available.
if [ -x /usr/bin/timeout ] ; then
- /usr/bin/timeout --foreground "$kselftest_timeout" $1
+ /usr/bin/timeout --foreground "$kselftest_timeout" \
+ /usr/bin/timeout "$kselftest_timeout" $1
else
$1
fi
base-commit: d528014517f2b0531862c02865b9d4c908019dc4
--
2.39.2