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<title>pm24.git/arch, branch master</title>
<subtitle>Unnamed repository; edit this file 'description' to name the repository.</subtitle>
<id>https://git.kobert.dev/pm24.git/atom/arch?h=master</id>
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<updated>2024-12-09T18:31:35Z</updated>
<entry>
<title>Merge tag 'perf_urgent_for_v6.13_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2024-12-09T18:31:35Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-12-09T18:31:35Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=e4c995f92b210ab353aa39e4c100ffc5d12eb13c'/>
<id>urn:sha1:e4c995f92b210ab353aa39e4c100ffc5d12eb13c</id>
<content type='text'>
Pull x86 perf fixes from Borislav Petkov:

 - Make sure the PEBS buffer is drained before reconfiguring the
   hardware

 - Add Arrow Lake U support

* tag 'perf_urgent_for_v6.13_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel/ds: Unconditionally drain PEBS DS when changing PEBS_DATA_CFG
  perf/x86/intel: Add Arrow Lake U support
</content>
</entry>
<entry>
<title>x86: Fix build regression with CONFIG_KEXEC_JUMP enabled</title>
<updated>2024-12-09T18:13:28Z</updated>
<author>
<name>Damien Le Moal</name>
<email>dlemoal@kernel.org</email>
</author>
<published>2024-12-08T23:53:32Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=aeb68937614f4aeceaaa762bd7f0212ce842b797'/>
<id>urn:sha1:aeb68937614f4aeceaaa762bd7f0212ce842b797</id>
<content type='text'>
Build 6.13-rc12 for x86_64 with gcc 14.2.1 fails with the error:

  ld: vmlinux.o: in function `virtual_mapped':
  linux/arch/x86/kernel/relocate_kernel_64.S:249:(.text+0x5915b): undefined reference to `saved_context_gdt_desc'

when CONFIG_KEXEC_JUMP is enabled.

This was introduced by commit 07fa619f2a40 ("x86/kexec: Restore GDT on
return from ::preserve_context kexec") which introduced a use of
saved_context_gdt_desc without a declaration for it.

Fix that by including asm/asm-offsets.h where saved_context_gdt_desc
is defined (indirectly in include/generated/asm-offsets.h which
asm/asm-offsets.h includes).

Fixes: 07fa619f2a40 ("x86/kexec: Restore GDT on return from ::preserve_context kexec")
Signed-off-by: Damien Le Moal &lt;dlemoal@kernel.org&gt;
Acked-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Acked-by: David Woodhouse &lt;dwmw@amazon.co.uk&gt;
Closes: https://lore.kernel.org/oe-kbuild-all/202411270006.ZyyzpYf8-lkp@intel.com/
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'x86_urgent_for_v6.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2024-12-08T19:38:56Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-12-08T19:38:56Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=84262262177b98cf4e57e8c010119576d3c6bc2b'/>
<id>urn:sha1:84262262177b98cf4e57e8c010119576d3c6bc2b</id>
<content type='text'>
Pull x86 fixes from Borislav Petkov:

 - Have the Automatic IBRS setting check on AMD does not falsely fire in
   the guest when it has been set already on the host

 - Make sure cacheinfo structures memory is allocated to address a boot
   NULL ptr dereference on Intel Meteor Lake which has different numbers
   of subleafs in its CPUID(4) leaf

 - Take care of the GDT restoring on the kexec path too, as expected by
   the kernel

 - Make sure SMP is not disabled when IO-APIC is disabled on the kernel
   cmdline

 - Add a PGD flag _PAGE_NOPTISHADOW to instruct machinery not to
   propagate changes to the kernelmode page tables, to the user portion,
   in PTI

 - Mark Intel Lunar Lake as affected by an issue where MONITOR wakeups
   can get lost and thus user-visible delays happen

 - Make sure PKRU is properly restored with XRSTOR on AMD after a PRKU
   write of 0 (WRPKRU) which will mark PKRU in its init state and thus
   lose the actual buffer

* tag 'x86_urgent_for_v6.13_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/CPU/AMD: WARN when setting EFER.AUTOIBRS if and only if the WRMSR fails
  x86/cacheinfo: Delete global num_cache_leaves
  cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU
  x86/kexec: Restore GDT on return from ::preserve_context kexec
  x86/cpu/topology: Remove limit of CPUs due to disabled IO/APIC
  x86/mm: Add _PAGE_NOPTISHADOW bit to avoid updating userspace page tables
  x86/cpu: Add Lunar Lake to list of CPUs with a broken MONITOR implementation
  x86/pkeys: Ensure updated PKRU value is XRSTOR'd
  x86/pkeys: Change caller of update_pkru_in_sigframe()
</content>
</entry>
<entry>
<title>Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux</title>
<updated>2024-12-06T21:47:55Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-12-06T21:47:55Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=f3ddc438a29f78f0642bfcf84407c236a0b2bdc7'/>
<id>urn:sha1:f3ddc438a29f78f0642bfcf84407c236a0b2bdc7</id>
<content type='text'>
Pull arm64 fixes from Catalin Marinas:
 "Nothing major, some left-overs from the recent merging window (MTE,
  coco) and some newly found issues like the ptrace() ones.

   - MTE/hugetlbfs:

      - Set VM_MTE_ALLOWED in the arch code and remove it from the core
        code for hugetlbfs mappings

      - Fix copy_highpage() warning when the source is a huge page but
        not MTE tagged, taking the wrong small page path

   - drivers/virt/coco:

      - Add the pKVM and Arm CCA drivers under the arm64 maintainership

      - Fix the pkvm driver to fall back to ioremap() (and warn) if the
        MMIO_GUARD hypercall fails

      - Keep the Arm CCA driver default 'n' rather than 'm'

   - A series of fixes for the arm64 ptrace() implementation,
     potentially leading to the kernel consuming uninitialised stack
     variables when PTRACE_SETREGSET is invoked with a length of 0

   - Fix zone_dma_limit calculation when RAM starts below 4GB and
     ZONE_DMA is capped to this limit

   - Fix early boot warning with CONFIG_DEBUG_VIRTUAL=y triggered by a
     call to page_to_phys() (from patch_map()) which checks pfn_valid()
     before vmemmap has been set up

   - Do not clobber bits 15:8 of the ASID used for TTBR1_EL1 and TLBI
     ops when the kernel assumes 8-bit ASIDs but running under a
     hypervisor on a system that implements 16-bit ASIDs (found running
     Linux under Parallels on Apple M4)

   - ACPI/IORT: Add PMCG platform information for HiSilicon HIP09A as it
     is using the same SMMU PMCG as HIP09 and suffers from the same
     errata

   - Add GCS to cpucap_is_possible(), missed in the recent merge"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: ptrace: fix partial SETREGSET for NT_ARM_GCS
  arm64: ptrace: fix partial SETREGSET for NT_ARM_POE
  arm64: ptrace: fix partial SETREGSET for NT_ARM_FPMR
  arm64: ptrace: fix partial SETREGSET for NT_ARM_TAGGED_ADDR_CTRL
  arm64: cpufeature: Add GCS to cpucap_is_possible()
  coco: virt: arm64: Do not enable cca guest driver by default
  arm64: mte: Fix copy_highpage() warning on hugetlb folios
  arm64: Ensure bits ASID[15:8] are masked out when the kernel uses 8-bit ASIDs
  ACPI/IORT: Add PMCG platform information for HiSilicon HIP09A
  MAINTAINERS: Add CCA and pKVM CoCO guest support to the ARM64 entry
  drivers/virt: pkvm: Don't fail ioremap() call if MMIO_GUARD fails
  arm64: patching: avoid early page_to_phys()
  arm64: mm: Fix zone_dma_limit calculation
  arm64: mte: set VM_MTE_ALLOWED for hugetlbfs at correct place
</content>
</entry>
<entry>
<title>x86/CPU/AMD: WARN when setting EFER.AUTOIBRS if and only if the WRMSR fails</title>
<updated>2024-12-06T18:57:05Z</updated>
<author>
<name>Sean Christopherson</name>
<email>seanjc@google.com</email>
</author>
<published>2024-12-06T16:20:06Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=492077668fb453b8b16c842fcf3fafc2ebc190e9'/>
<id>urn:sha1:492077668fb453b8b16c842fcf3fafc2ebc190e9</id>
<content type='text'>
When ensuring EFER.AUTOIBRS is set, WARN only on a negative return code
from msr_set_bit(), as '1' is used to indicate the WRMSR was successful
('0' indicates the MSR bit was already set).

Fixes: 8cc68c9c9e92 ("x86/CPU/AMD: Make sure EFER[AIBRSE] is set")
Reported-by: Nathan Chancellor &lt;nathan@kernel.org&gt;
Signed-off-by: Sean Christopherson &lt;seanjc@google.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Link: https://lore.kernel.org/r/Z1MkNofJjt7Oq0G6@google.com
Closes: https://lore.kernel.org/all/20241205220604.GA2054199@thelio-3990X
</content>
</entry>
<entry>
<title>x86/cacheinfo: Delete global num_cache_leaves</title>
<updated>2024-12-06T12:13:36Z</updated>
<author>
<name>Ricardo Neri</name>
<email>ricardo.neri-calderon@linux.intel.com</email>
</author>
<published>2024-11-28T00:22:47Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=9677be09e5e4fbe48aeccb06ae3063c5eba331c3'/>
<id>urn:sha1:9677be09e5e4fbe48aeccb06ae3063c5eba331c3</id>
<content type='text'>
Linux remembers cpu_cachinfo::num_leaves per CPU, but x86 initializes all
CPUs from the same global "num_cache_leaves".

This is erroneous on systems such as Meteor Lake, where each CPU has a
distinct num_leaves value. Delete the global "num_cache_leaves" and
initialize num_leaves on each CPU.

init_cache_level() no longer needs to set num_leaves. Also, it never had to
set num_levels as it is unnecessary in x86. Keep checking for zero cache
leaves. Such condition indicates a bug.

  [ bp: Cleanup. ]

Signed-off-by: Ricardo Neri &lt;ricardo.neri-calderon@linux.intel.com&gt;
Signed-off-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Cc: stable@vger.kernel.org # 6.3+
Link: https://lore.kernel.org/r/20241128002247.26726-3-ricardo.neri-calderon@linux.intel.com
</content>
</entry>
<entry>
<title>x86/kexec: Restore GDT on return from ::preserve_context kexec</title>
<updated>2024-12-06T09:35:49Z</updated>
<author>
<name>David Woodhouse</name>
<email>dwmw@amazon.co.uk</email>
</author>
<published>2024-12-05T15:05:07Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=07fa619f2a40c221ea27747a3323cabc59ab25eb'/>
<id>urn:sha1:07fa619f2a40c221ea27747a3323cabc59ab25eb</id>
<content type='text'>
The restore_processor_state() function explicitly states that "the asm code
that gets us here will have restored a usable GDT". That wasn't true in the
case of returning from a ::preserve_context kexec. Make it so.

Without this, the kernel was depending on the called function to reload a
GDT which is appropriate for the kernel before returning.

Test program:

 #include &lt;unistd.h&gt;
 #include &lt;errno.h&gt;
 #include &lt;stdio.h&gt;
 #include &lt;stdlib.h&gt;
 #include &lt;linux/kexec.h&gt;
 #include &lt;linux/reboot.h&gt;
 #include &lt;sys/reboot.h&gt;
 #include &lt;sys/syscall.h&gt;

 int main (void)
 {
        struct kexec_segment segment = {};
	unsigned char purgatory[] = {
		0x66, 0xba, 0xf8, 0x03,	// mov $0x3f8, %dx
		0xb0, 0x42,		// mov $0x42, %al
		0xee,			// outb %al, (%dx)
		0xc3,			// ret
	};
	int ret;

	segment.buf = &amp;purgatory;
	segment.bufsz = sizeof(purgatory);
	segment.mem = (void *)0x400000;
	segment.memsz = 0x1000;
	ret = syscall(__NR_kexec_load, 0x400000, 1, &amp;segment, KEXEC_PRESERVE_CONTEXT);
	if (ret) {
		perror("kexec_load");
		exit(1);
	}

	ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, LINUX_REBOOT_CMD_KEXEC);
	if (ret) {
		perror("kexec reboot");
		exit(1);
	}
	printf("Success\n");
	return 0;
 }

Signed-off-by: David Woodhouse &lt;dwmw@amazon.co.uk&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20241205153343.3275139-2-dwmw2@infradead.org
</content>
</entry>
<entry>
<title>arm64: ptrace: fix partial SETREGSET for NT_ARM_GCS</title>
<updated>2024-12-05T18:05:51Z</updated>
<author>
<name>Mark Rutland</name>
<email>mark.rutland@arm.com</email>
</author>
<published>2024-12-05T12:16:55Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=d60624f72d15862a96965b945f6ddfee9a1359e7'/>
<id>urn:sha1:d60624f72d15862a96965b945f6ddfee9a1359e7</id>
<content type='text'>
Currently gcs_set() doesn't initialize the temporary 'user_gcs'
variable, and a SETREGSET call with a length of 0, 8, or 16 will leave
some portion of this uninitialized. Consequently some arbitrary
uninitialized values may be written back to the relevant fields in task
struct, potentially leaking up to 192 bits of memory from the kernel
stack. The read is limited to a specific slot on the stack, and the
issue does not provide a write mechanism.

As gcs_set() rejects cases where user_gcs::features_enabled has bits set
other than PR_SHADOW_STACK_SUPPORTED_STATUS_MASK, a SETREGSET call with
a length of zero will randomly succeed or fail depending on the value of
the uninitialized value, it isn't possible to leak the full 192 bits.
With a length of 8 or 16, user_gcs::features_enabled can be initialized
to an accepted value, making it practical to leak 128 or 64 bits.

Fix this by initializing the temporary value before copying the regset
from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG,
NT_ARM_SYSTEM_CALL). In the case of a zero-length or partial write, the
existing contents of the fields which are not written to will be
retained.

To ensure that the extraction and insertion of fields is consistent
across the GETREGSET and SETREGSET calls, new task_gcs_to_user() and
task_gcs_from_user() helpers are added, matching the style of
pac_address_keys_to_user() and pac_address_keys_from_user().

Before this patch:

| # ./gcs-test
| Attempting to write NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x0000000000000000,
|     .gcspr_el0        = 0x900d900d900d900d,
| }
| SETREGSET(nt=0x410, len=24) wrote 24 bytes
|
| Attempting to read NT_ARM_GCS::user_gcs
| GETREGSET(nt=0x410, len=24) read 24 bytes
| Read NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x0000000000000000,
|     .gcspr_el0        = 0x900d900d900d900d,
| }
|
| Attempting partial write NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x1de7ec7edbadc0de,
|     .gcspr_el0        = 0x1de7ec7edbadc0de,
| }
| SETREGSET(nt=0x410, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_GCS::user_gcs
| GETREGSET(nt=0x410, len=24) read 24 bytes
| Read NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x000000000093e780,
|     .gcspr_el0        = 0xffff800083a63d50,
| }

After this patch:

| # ./gcs-test
| Attempting to write NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x0000000000000000,
|     .gcspr_el0        = 0x900d900d900d900d,
| }
| SETREGSET(nt=0x410, len=24) wrote 24 bytes
|
| Attempting to read NT_ARM_GCS::user_gcs
| GETREGSET(nt=0x410, len=24) read 24 bytes
| Read NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x0000000000000000,
|     .gcspr_el0        = 0x900d900d900d900d,
| }
|
| Attempting partial write NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x1de7ec7edbadc0de,
|     .gcspr_el0        = 0x1de7ec7edbadc0de,
| }
| SETREGSET(nt=0x410, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_GCS::user_gcs
| GETREGSET(nt=0x410, len=24) read 24 bytes
| Read NT_ARM_GCS::user_gcs = {
|     .features_enabled = 0x0000000000000000,
|     .features_locked  = 0x0000000000000000,
|     .gcspr_el0        = 0x900d900d900d900d,
| }

Fixes: 7ec3b57cb29f ("arm64/ptrace: Expose GCS via ptrace and core files")
Signed-off-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Mark Brown &lt;broonie@kernel.org&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Reviewed-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20241205121655.1824269-5-mark.rutland@arm.com
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</content>
</entry>
<entry>
<title>arm64: ptrace: fix partial SETREGSET for NT_ARM_POE</title>
<updated>2024-12-05T18:05:33Z</updated>
<author>
<name>Mark Rutland</name>
<email>mark.rutland@arm.com</email>
</author>
<published>2024-12-05T12:16:54Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=594bfc4947c4fcabba1318d8384c61a29a6b89fb'/>
<id>urn:sha1:594bfc4947c4fcabba1318d8384c61a29a6b89fb</id>
<content type='text'>
Currently poe_set() doesn't initialize the temporary 'ctrl' variable,
and a SETREGSET call with a length of zero will leave this
uninitialized. Consequently an arbitrary value will be written back to
target-&gt;thread.por_el0, potentially leaking up to 64 bits of memory from
the kernel stack. The read is limited to a specific slot on the stack,
and the issue does not provide a write mechanism.

Fix this by initializing the temporary value before copying the regset
from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG,
NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing
contents of POR_EL1 will be retained.

Before this patch:

| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d
|
| Attempting to write NT_ARM_POE (zero length)
| SETREGSET(nt=0x40f, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0xffff8000839c3d50

After this patch:

| # ./poe-test
| Attempting to write NT_ARM_POE::por_el0 = 0x900d900d900d900d
| SETREGSET(nt=0x40f, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d
|
| Attempting to write NT_ARM_POE (zero length)
| SETREGSET(nt=0x40f, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_POE::por_el0
| GETREGSET(nt=0x40f, len=8) read 8 bytes
| Read NT_ARM_POE::por_el0 = 0x900d900d900d900d

Fixes: 175198199262 ("arm64/ptrace: add support for FEAT_POE")
Cc: &lt;stable@vger.kernel.org&gt; # 6.12.x
Signed-off-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Joey Gouly &lt;joey.gouly@arm.com&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Reviewed-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20241205121655.1824269-4-mark.rutland@arm.com
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</content>
</entry>
<entry>
<title>arm64: ptrace: fix partial SETREGSET for NT_ARM_FPMR</title>
<updated>2024-12-05T18:04:06Z</updated>
<author>
<name>Mark Rutland</name>
<email>mark.rutland@arm.com</email>
</author>
<published>2024-12-05T12:16:53Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=f5d71291841aecfe5d8435da2dfa7f58ccd18bc8'/>
<id>urn:sha1:f5d71291841aecfe5d8435da2dfa7f58ccd18bc8</id>
<content type='text'>
Currently fpmr_set() doesn't initialize the temporary 'fpmr' variable,
and a SETREGSET call with a length of zero will leave this
uninitialized. Consequently an arbitrary value will be written back to
target-&gt;thread.uw.fpmr, potentially leaking up to 64 bits of memory from
the kernel stack. The read is limited to a specific slot on the stack,
and the issue does not provide a write mechanism.

Fix this by initializing the temporary value before copying the regset
from userspace, as for other regsets (e.g. NT_PRSTATUS, NT_PRFPREG,
NT_ARM_SYSTEM_CALL). In the case of a zero-length write, the existing
contents of FPMR will be retained.

Before this patch:

| # ./fpmr-test
| Attempting to write NT_ARM_FPMR::fpmr = 0x900d900d900d900d
| SETREGSET(nt=0x40e, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_FPMR::fpmr
| GETREGSET(nt=0x40e, len=8) read 8 bytes
| Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d
|
| Attempting to write NT_ARM_FPMR (zero length)
| SETREGSET(nt=0x40e, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_FPMR::fpmr
| GETREGSET(nt=0x40e, len=8) read 8 bytes
| Read NT_ARM_FPMR::fpmr = 0xffff800083963d50

After this patch:

| # ./fpmr-test
| Attempting to write NT_ARM_FPMR::fpmr = 0x900d900d900d900d
| SETREGSET(nt=0x40e, len=8) wrote 8 bytes
|
| Attempting to read NT_ARM_FPMR::fpmr
| GETREGSET(nt=0x40e, len=8) read 8 bytes
| Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d
|
| Attempting to write NT_ARM_FPMR (zero length)
| SETREGSET(nt=0x40e, len=0) wrote 0 bytes
|
| Attempting to read NT_ARM_FPMR::fpmr
| GETREGSET(nt=0x40e, len=8) read 8 bytes
| Read NT_ARM_FPMR::fpmr = 0x900d900d900d900d

Fixes: 4035c22ef7d4 ("arm64/ptrace: Expose FPMR via ptrace")
Cc: &lt;stable@vger.kernel.org&gt; # 6.9.x
Signed-off-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Mark Brown &lt;broonie@kernel.org&gt;
Cc: Will Deacon &lt;will@kernel.org&gt;
Reviewed-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20241205121655.1824269-3-mark.rutland@arm.com
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
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