[PATCH v2 0/2] Use __u128 in arm64 UAPI headers

[PATCH v2 0/2] Use __u128 in arm64 UAPI headers

[Will Deacon]

Hi folks,

This is version two of the patch I previously sent here:

  https://lore.kernel.org/r/20260619130835.5678-1-will@kernel.org

I even briefly queued that version up, but it exploded spectacularly
when building the kselftests for arm64 [1] [2]. So the only change since
v1 is the addition of a preliminary patch that adds the '__u128' typedef
to the private copy of linux/types.h used by the tools/ directory.

I plan to take this all via the arm64 tree unless anybody objects.

Cheers,

Will

[1] https://lore.kernel.org/r/202606240441.7eZ1TIRM-lkp@intel.com
[2] https://lore.kernel.org/r/ajvGS7UBpWzJtzkw@sirena.org.uk

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Steffen Eiden <seiden@linux.ibm.com>
Cc: Andreas Grapentin <gra@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>

--->8

Will Deacon (2):
  tools: linux/types.h: Add 128-bit integer types for arm64 UAPI
    structures
  arm64: uapi: Use __u128 instead of __uint128_t in UAPI headers

 arch/arm64/include/uapi/asm/ptrace.h     | 12 ++++++------
 arch/arm64/include/uapi/asm/sigcontext.h |  6 +++---
 tools/include/linux/types.h              |  5 +++++
 3 files changed, 14 insertions(+), 9 deletions(-)

-- 
2.55.0.rc0.799.gd6f94ed593-goog

[PATCH v2 1/2] tools: linux/types.h: Add 128-bit integer types for arm64 UAPI structures

[Will Deacon]

The arm64 UAPI exposes some 128-bit integer types to represent things
such as fpsimd registers in the sigcontext. In preparation for defining
these using the '__u128' typedef implemented by uapi/linux/types.h, copy
that typedef over to the private linux/types.h header used by the tools
directory.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Matlack <dmatlack@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 tools/include/linux/types.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/include/linux/types.h b/tools/include/linux/types.h
index d41f8a261bce..b6c473b7920d 100644
--- a/tools/include/linux/types.h
+++ b/tools/include/linux/types.h
@@ -23,6 +23,11 @@ typedef enum {
 	__GFP_HIGH
 } gfp_t;
 
+#ifdef __SIZEOF_INT128__
+typedef __signed__ __int128 __s128 __attribute__((aligned(16)));
+typedef unsigned __int128 __u128 __attribute__((aligned(16)));
+#endif
+
 /*
  * We define u64 as uint64_t for every architecture
  * so that we can print it with "%"PRIx64 without getting warnings.
-- 
2.55.0.rc0.799.gd6f94ed593-goog

[PATCH v2 2/2] arm64: uapi: Use __u128 instead of __uint128_t in UAPI headers

[Will Deacon]

The arm64 UAPI exposes '__uint128_t' types in the members of
'struct user_fpsimd_state', 'struct user_pac_address_keys' and in the
signal frame via 'struct fpsimd_context'. Since the alignment of such
a type appears to be non-portable (16 bytes on arm64, 8 bytes on s390),
prefer the '__u128' typedef from uapi/linux/types.h, which makes the
alignment explicit and allows the definitions to be reused by other
host architectures.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Steffen Eiden <seiden@linux.ibm.com>
Cc: Andreas Grapentin <gra@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/include/uapi/asm/ptrace.h     | 12 ++++++------
 arch/arm64/include/uapi/asm/sigcontext.h |  6 +++---
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index 6fed93fb2536..15649a253a57 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h
@@ -93,7 +93,7 @@ struct user_pt_regs {
 };
 
 struct user_fpsimd_state {
-	__uint128_t	vregs[32];
+	__u128		vregs[32];
 	__u32		fpsr;
 	__u32		fpcr;
 	__u32		__reserved[2];
@@ -258,14 +258,14 @@ struct user_pac_mask {
 /* pointer authentication keys (NT_ARM_PACA_KEYS, NT_ARM_PACG_KEYS) */
 
 struct user_pac_address_keys {
-	__uint128_t	apiakey;
-	__uint128_t	apibkey;
-	__uint128_t	apdakey;
-	__uint128_t	apdbkey;
+	__u128	apiakey;
+	__u128	apibkey;
+	__u128	apdakey;
+	__u128	apdbkey;
 };
 
 struct user_pac_generic_keys {
-	__uint128_t	apgakey;
+	__u128	apgakey;
 };
 
 /* ZA state (NT_ARM_ZA) */
diff --git a/arch/arm64/include/uapi/asm/sigcontext.h b/arch/arm64/include/uapi/asm/sigcontext.h
index e29bf3e2d0cc..d250ca7a1d46 100644
--- a/arch/arm64/include/uapi/asm/sigcontext.h
+++ b/arch/arm64/include/uapi/asm/sigcontext.h
@@ -78,7 +78,7 @@ struct fpsimd_context {
 	struct _aarch64_ctx head;
 	__u32 fpsr;
 	__u32 fpcr;
-	__uint128_t vregs[32];
+	__u128 vregs[32];
 };
 
 /*
@@ -266,8 +266,8 @@ struct gcs_context {
  *	-	----				-----------
  *	REGS					the entire SVE context
  *
- *	ZREGS	__uint128_t[SVE_NUM_ZREGS][vq]	all Z-registers
- *	ZREG	__uint128_t[vq]			individual Z-register Zn
+ *	ZREGS	__u128[SVE_NUM_ZREGS][vq]	all Z-registers
+ *	ZREG	__u128[vq]			individual Z-register Zn
  *
  *	PREGS	uint16_t[SVE_NUM_PREGS][vq]	all P-registers
  *	PREG	uint16_t[vq]			individual P-register Pn
-- 
2.55.0.rc0.799.gd6f94ed593-goog

Re: [PATCH v2 0/2] Use __u128 in arm64 UAPI headers

[Will Deacon]

On Fri, 26 Jun 2026 15:17:27 +0100, Will Deacon wrote:
> This is version two of the patch I previously sent here:
> 
>   https://lore.kernel.org/r/20260619130835.5678-1-will@kernel.org
> 
> I even briefly queued that version up, but it exploded spectacularly
> when building the kselftests for arm64 [1] [2]. So the only change since
> v1 is the addition of a preliminary patch that adds the '__u128' typedef
> to the private copy of linux/types.h used by the tools/ directory.
> 
> [...]

Applied to arm64 (for-next/uapi), thanks!

[1/2] tools: linux/types.h: Add 128-bit integer types for arm64 UAPI structures
      https://git.kernel.org/arm64/c/10a47fb67340
[2/2] arm64: uapi: Use __u128 instead of __uint128_t in UAPI headers
      https://git.kernel.org/arm64/c/d4bf9e08d412

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

Re: [PATCH v2 0/2] Use __u128 in arm64 UAPI headers

[Jeremy Linton]

Hi,

On 6/26/26 9:17 AM, Will Deacon wrote:
> Hi folks,
> 
> This is version two of the patch I previously sent here:
> 
>    https://lore.kernel.org/r/20260619130835.5678-1-will@kernel.org
> 
> I even briefly queued that version up, but it exploded spectacularly
> when building the kselftests for arm64 [1] [2]. So the only change since
> v1 is the addition of a preliminary patch that adds the '__u128' typedef
> to the private copy of linux/types.h used by the tools/ directory.
> 
> I plan to take this all via the arm64 tree unless anybody objects.

This seems to be creating a interesting situation that the follow-on 
commit:
10a47fb67340 tools: linux/types.h: Add 128-bit integer types for arm64 
UAPI structures

Is missing from older kernel tooling/etc, which means the tools that end 
up pulling this header in won't build on machines running 7.3 kernel 
headers.

AKA, build/install master, switch back to an older branch and discover 
say bpftool won't build anymore.



Thanks,


> 
> Cheers,
> 
> Will
> 
> [1] https://lore.kernel.org/r/202606240441.7eZ1TIRM-lkp@intel.com
> [2] https://lore.kernel.org/r/ajvGS7UBpWzJtzkw@sirena.org.uk
> 
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
> Cc: David Matlack <dmatlack@google.com>
> Cc: Steffen Eiden <seiden@linux.ibm.com>
> Cc: Andreas Grapentin <gra@linux.ibm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Dave Martin <dave.martin@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> 
> --->8
> 
> Will Deacon (2):
>    tools: linux/types.h: Add 128-bit integer types for arm64 UAPI
>      structures
>    arm64: uapi: Use __u128 instead of __uint128_t in UAPI headers
> 
>   arch/arm64/include/uapi/asm/ptrace.h     | 12 ++++++------
>   arch/arm64/include/uapi/asm/sigcontext.h |  6 +++---
>   tools/include/linux/types.h              |  5 +++++
>   3 files changed, 14 insertions(+), 9 deletions(-)
> 

Re: [PATCH v2 0/2] Use __u128 in arm64 UAPI headers

[Will Deacon]

On Wed, Sep 02, 2026 at 09:21:32PM -0500, Jeremy Linton wrote:
> On 6/26/26 9:17 AM, Will Deacon wrote:
> > This is version two of the patch I previously sent here:
> > 
> >    https://lore.kernel.org/r/20260619130835.5678-1-will@kernel.org
> > 
> > I even briefly queued that version up, but it exploded spectacularly
> > when building the kselftests for arm64 [1] [2]. So the only change since
> > v1 is the addition of a preliminary patch that adds the '__u128' typedef
> > to the private copy of linux/types.h used by the tools/ directory.
> > 
> > I plan to take this all via the arm64 tree unless anybody objects.
> 
> This seems to be creating a interesting situation that the follow-on commit:
> 10a47fb67340 tools: linux/types.h: Add 128-bit integer types for arm64 UAPI
> structures
> 
> Is missing from older kernel tooling/etc, which means the tools that end up
> pulling this header in won't build on machines running 7.3 kernel headers.
> 
> AKA, build/install master, switch back to an older branch and discover say
> bpftool won't build anymore.

Ah, I guess we need to backport 10a47fb67340 to stable, then?

Will