[PATCH V17 0/8] Rust Support for powerpc

[PATCH V17 0/8] Rust Support for powerpc

[Mukesh Kumar Chaurasiya (IBM)]

Enable experimental rust support for ppc64le and ppc32be. The patch for
ppc32 has been provided by Link Mauve[1] and ppc64le support[2] has been
merged over it. ppc32 needs some toolchain fixes mentioned in the patch
`rust: Add PowerPC support` and the discussion for that is done here[1].

This has been tested on
- powernv9 hardware
- pseries P11 hardware
- pseries(9, 10) qemu
- powernv(9, 10) qemu
- rustdoc on x86 and powerpc64le
- rusttest on x86 and powerpc64le

We are actively working with our LLVM team to get the target for ppc,
ppc64 and ppc64le in the rust compiler.

[1] https://lore.kernel.org/all/20260204030507.8203-1-linkmauve@linkmauve.fr
[2] https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com

Changelog:
V16 -> V17:
- Rebased to latest v7.2-rc2 

V15 -> V16:
- Rebased to latest v7.1-rc4
V15: https://lore.kernel.org/all/20260426105932.2270364-1-mkchauras@gmail.com/

V14 -> V15:
- Fix an issue with rustdoc build on ppc64le
V14: https://lore.kernel.org/all/20260426085725.2090827-1-mkchauras@gmail.com/

V13 -> V14:
- 2nd patch is rewritten (Christian)
- Fixed a small typo in rust/Makefile (Sashiko)
- Fixed commit message in Patch 4 (Sashiko)
V13: https://lore.kernel.org/all/20260424054742.45832-1-mkchauras@gmail.com/

V12 -> V13:
- Added a patch for fixing build issue on ppc32 by Link Mauve
- Added another patch to fix a build issue in dma-buf
- Added another patch to enforce minimum `rustc` version for powerpc
V12: https://lore.kernel.org/all/20260421120958.190430-1-mkchauras@gmail.com/

V11 -> V12:
- Rebased to mainline (rust/Makefile conflict resolved)
V11: https://lore.kernel.org/all/20260417152253.2312961-1-mkchauras@gmail.com/

V10 -> V11:
- Updated `rust/Makefile`
- Not all libraries are move to `rust/host` directory now. Only
  proc_macro2, quote and syn are moved
- Special handling for pin init is added. Details in commit
- Removed mkdir for `rust/host`, this is now handled by toolchain.
V10: https://lore.kernel.org/all/20260406200149.3727922-1-mkchauras@gmail.com/

V9 -> V10:
- rust/Makefile updated with review comments from Miguel
- Patch 1/4 updated with commit message and subject
V9: https://lore.kernel.org/all/20260404121610.1956528-1-mkchauras@gmail.com/

V8 -> V9:
- rust/Makefile updated with a directory instead of abspath
V8: https://lore.kernel.org/all/20260403145308.1042622-1-mkchauras@gmail.com/

V7 -> V8:
- rust/Makefile updated to separate host libraries from target
V7: https://lore.kernel.org/all/20260329160254.2592207-1-mkchauras@gmail.com/

Changelog:
V6 -> V7:
- Documentation removed as powerpc is still under development
- Added a fix for race condition in rust/Makefile
V6: https://lore.kernel.org/all/20260210090023.2587534-1-mkchauras@gmail.com

V5 -> V6:
- Added a missing Tested by from Venkat which got missed since V3
- Support is marked as Maintained instead of experimental
V5: https://lore.kernel.org/all/20260210053756.2088302-1-mkchauras@gmail.com

V4 -> V5:
- Removed a nested ifdef from PPC64 for Little endian toolchain
V4: https://lore.kernel.org/all/20260209105456.1551677-1-mkchauras@gmail.com

V3 -> V4:
- Co-developed-by header added in patch 1
V3: https://lore.kernel.org/all/20260205180429.3280657-1-mkchauras@gmail.com

V2 -> V3:
- Splited HAVE_RUST in 2 lines
- BINDGEN_TARGET_powerpc initialized before assigning the same to
  BINDGEN_TARGET
V2: https://lore.kernel.org/all/20260204210125.613350-1-mkchauras@gmail.com

V1 -> V2:
- jump label fix for rust has been moved to a separate patch
- PPC32 support has been taken
- rust support has been marked experimental
- target.json dependency has been removed
- HAVE_RUST now depends on CPU_LITTLE_ENDIAN for PPC64
V1: https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com 

Link Mauve (2):
  rust: Make __udivdi3() and __umoddi3() panic
  rust: Add PowerPC support

Mukesh Kumar Chaurasiya (IBM) (6):
  powerpc/syscall: Fix syscall skip handling for seccomp and ptrace
  rust: Fix "multiple candidates for rmeta dependency core" error
  dma-resv: Fix undefined symbol when CONFIG_DMA_SHARED_BUFFER is
    disabled
  powerpc/jump_label: adjust inline asm to be consistent
  rust/powerpc: Set min rustc version for powerpc
  powerpc: Enable Rust for ppc64le

 arch/powerpc/Kconfig                   |  2 +
 arch/powerpc/Makefile                  |  7 ++++
 arch/powerpc/include/asm/jump_label.h  | 23 ++++++-----
 arch/powerpc/include/asm/ptrace.h      | 22 +++++++++-
 arch/powerpc/include/asm/syscall.h     |  6 +++
 arch/powerpc/include/uapi/asm/ptrace.h |  6 ++-
 arch/powerpc/kernel/ptrace/ptrace.c    |  2 +
 arch/powerpc/kernel/syscall.c          | 18 +++++++++
 rust/Makefile                          | 56 +++++++++++++++++---------
 rust/compiler_builtins.rs              |  6 +++
 rust/helpers/helpers.c                 |  2 +
 scripts/min-tool-version.sh            |  2 +
 12 files changed, 119 insertions(+), 33 deletions(-)

-- 
2.55.0

[PATCH V17 1/8] powerpc/syscall: Fix syscall skip handling for seccomp and ptrace

[Mukesh Kumar Chaurasiya (IBM)]

After enabling GENERIC_ENTRY on PowerPC, syscall_enter_from_user_mode()
returns -1 as a sentinel to signal that seccomp or ptrace has intercepted
the syscall and already set a return value via syscall_set_return_value().
system_call_exception() was not handling this sentinel, and since -1UL
is >= NR_syscalls, the code fell into the out-of-range path and returned
-ENOSYS, overwriting the errno already placed in regs->gpr[3].

The naive fix of checking r0 == -1L before the NR_syscalls bounds check
is ambiguous: a user legitimately calling syscall(-1) also produces r0 ==
-1L, and a tracer intercepting such a call would have its injected return
value silently discarded.

Fix this properly by introducing regs->entry_flags, a kernel-internal
field in struct pt_regs (consuming one slot of the existing __pt_regs_pad
so the ABI is preserved), with SYSCALL_ENTRY_RET_SET as an out-of-band
flag. syscall_set_return_value() sets this flag whenever seccomp or ptrace
injects a return value. system_call_exception() zeros entry_flags before
calling syscall_enter_from_user_mode(), then checks and clears the flag
afterwards: if set, it returns regs->gpr[3] directly regardless of what
syscall number the user originally requested.

This handles all seccomp actions correctly:

  - SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE (no tracer), SECCOMP_RET_USER_NOTIF:
    all call syscall_set_return_value(), flag is set, injected value returned.
  - SECCOMP_RET_TRAP, SECCOMP_RET_KILL: call syscall_rollback() and deliver
    a signal; flag is not set, but the process is dying so the return value
    is irrelevant.

The fix covers both ppc32 and ppc64 with no #ifdefs.

Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
Reported-by: Michal Suchánek <msuchanek@suse.de>
Closes: https://lore.kernel.org/all/ajpp-_XnbF3UTM_E@kunlun.suse.cz/
Tested-by: Michal Suchánek <msuchanek@suse.de>
Reviewed-by: Michal Suchánek <msuchanek@suse.de>
Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
---
 arch/powerpc/include/asm/ptrace.h      | 22 +++++++++++++++++++++-
 arch/powerpc/include/asm/syscall.h     |  6 ++++++
 arch/powerpc/include/uapi/asm/ptrace.h |  6 ++++--
 arch/powerpc/kernel/ptrace/ptrace.c    |  2 ++
 arch/powerpc/kernel/syscall.c          | 18 ++++++++++++++++++
 5 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index fdeb97421785..1a53d5cfa8db 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -54,8 +54,9 @@ struct pt_regs
 			};
 			unsigned long result;
 			unsigned long exit_flags;
+			unsigned long entry_flags;
 			/* Maintain 16 byte interrupt stack alignment */
-			unsigned long __pt_regs_pad[3];
+			unsigned long __pt_regs_pad[2];
 		};
 	};
 #if defined(CONFIG_PPC64) || defined(CONFIG_PPC_KUAP)
@@ -233,6 +234,25 @@ static inline unsigned long frame_pointer(struct pt_regs *regs)
 #define current_pt_regs() \
 	((struct pt_regs *)((unsigned long)task_stack_page(current) + THREAD_SIZE) - 1)
 
+/*
+ * SYSCALL_ENTRY_RET_SET: seccomp or ptrace called syscall_set_return_value()
+ * and wants the syscall skipped; regs->gpr[3] already holds the return value.
+ */
+#define SYSCALL_ENTRY_RET_SET	BIT(0)
+
+static inline void set_syscall_entry_ret(struct pt_regs *regs)
+{
+	regs->entry_flags |= SYSCALL_ENTRY_RET_SET;
+}
+
+static inline bool test_and_clear_syscall_entry_ret(struct pt_regs *regs)
+{
+	bool set = !!(regs->entry_flags & SYSCALL_ENTRY_RET_SET);
+
+	regs->entry_flags &= ~SYSCALL_ENTRY_RET_SET;
+	return set;
+}
+
 /*
  * The 4 low bits (0xf) are available as flags to overload the trap word,
  * because interrupt vectors have minimum alignment of 0x10. TRAP_FLAGS_MASK
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 834fcc4f7b54..9ae79326abe3 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -98,6 +98,12 @@ static inline void syscall_set_return_value(struct task_struct *task,
 			regs->gpr[3] = val;
 		}
 	}
+	/*
+	 * Mark that a return value has been explicitly set by seccomp or
+	 * ptrace so that system_call_exception() can skip the syscall
+	 * unconditionally, even when the user requested syscall(-1).
+	 */
+	set_syscall_entry_ret(regs);
 }
 
 static inline void syscall_get_arguments(struct task_struct *task,
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index a393b7f2760a..2f2a43414fe6 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -56,7 +56,8 @@ struct pt_regs
 	unsigned long dsisr;		/* on 4xx/Book-E used for ESR */
 	unsigned long result;		/* Result of a system call */
 	unsigned long exit_flags;	/* System call exit flags */
-	unsigned long __pt_regs_pad[3];	/* Maintain 16 byte interrupt stack alignment */
+	unsigned long entry_flags;	/* System call entry flags */
+	unsigned long __pt_regs_pad[2];	/* Maintain 16 byte interrupt stack alignment */
 };
 
 #endif /* __ASSEMBLER__ */
@@ -117,7 +118,8 @@ struct pt_regs
 #define PT_DSISR 42
 #define PT_RESULT 43
 #define PT_EXIT_FLAGS 44
-#define PT_PAD 47 /* 3 times */
+#define PT_ENTRY_FLAGS 45
+#define PT_PAD 46 /* 2 times */
 #define PT_DSCR 48
 #define PT_REGS_COUNT 48
 
diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
index 316d4f5ead8e..440d00690cf2 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -235,6 +235,8 @@ void __init pt_regs_check(void)
 		     offsetof(struct user_pt_regs, dsisr));
 	BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
 		     offsetof(struct user_pt_regs, result));
+	BUILD_BUG_ON(offsetof(struct pt_regs, entry_flags) !=
+		     offsetof(struct user_pt_regs, entry_flags));
 
 	BUILD_BUG_ON(sizeof(struct user_pt_regs) > sizeof(struct pt_regs));
 
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index a9da2af6efa8..a43d3a9428cc 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -19,9 +19,27 @@ notrace long system_call_exception(struct pt_regs *regs, unsigned long r0)
 	long ret;
 	syscall_fn f;
 
+	/*
+	 * Zero entry_flags before syscall_enter_from_user_mode() so that
+	 * syscall_set_return_value() can set SYSCALL_ENTRY_RET_SET as an
+	 * unambiguous out-of-band signal.  The field is not initialised by
+	 * the entry assembly.
+	 */
+	regs->entry_flags = 0;
 	add_random_kstack_offset();
 	r0 = syscall_enter_from_user_mode(regs, r0);
 
+	/*
+	 * Seccomp or ptrace may have set a return value and requested that
+	 * the syscall be skipped. syscall_set_return_value() sets
+	 * SYSCALL_ENTRY_RET_SET in regs->entry_flags as an
+	 * unambiguous out-of-band signal. This avoids the ambiguity of
+	 * using r0 == -1 as the skip sentinel when the user themselves
+	 * called syscall(-1).
+	 */
+	if (unlikely(test_and_clear_syscall_entry_ret(regs)))
+		return syscall_get_error(current, regs);
+
 	if (unlikely(r0 >= NR_syscalls)) {
 		if (unlikely(trap_is_unsupported_scv(regs))) {
 			/* Unsupported scv vector */
-- 
2.55.0

Re: [PATCH V17 0/8] Rust Support for powerpc

[Mukesh Kumar Chaurasiya]

On Wed, Jul 08, 2026 at 01:46:25PM +0530, Mukesh Kumar Chaurasiya (IBM) wrote:
> Enable experimental rust support for ppc64le and ppc32be. The patch for
> ppc32 has been provided by Link Mauve[1] and ppc64le support[2] has been
> merged over it. ppc32 needs some toolchain fixes mentioned in the patch
> `rust: Add PowerPC support` and the discussion for that is done here[1].
> 
> This has been tested on
> - powernv9 hardware
> - pseries P11 hardware
> - pseries(9, 10) qemu
> - powernv(9, 10) qemu
> - rustdoc on x86 and powerpc64le
> - rusttest on x86 and powerpc64le
> 
> We are actively working with our LLVM team to get the target for ppc,
> ppc64 and ppc64le in the rust compiler.
> 
> [1] https://lore.kernel.org/all/20260204030507.8203-1-linkmauve@linkmauve.fr
> [2] https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com
> 
> Changelog:
> V16 -> V17:
> - Rebased to latest v7.2-rc2 
> 
> V15 -> V16:
> - Rebased to latest v7.1-rc4
> V15: https://lore.kernel.org/all/20260426105932.2270364-1-mkchauras@gmail.com/
> 
> V14 -> V15:
> - Fix an issue with rustdoc build on ppc64le
> V14: https://lore.kernel.org/all/20260426085725.2090827-1-mkchauras@gmail.com/
> 
> V13 -> V14:
> - 2nd patch is rewritten (Christian)
> - Fixed a small typo in rust/Makefile (Sashiko)
> - Fixed commit message in Patch 4 (Sashiko)
> V13: https://lore.kernel.org/all/20260424054742.45832-1-mkchauras@gmail.com/
> 
> V12 -> V13:
> - Added a patch for fixing build issue on ppc32 by Link Mauve
> - Added another patch to fix a build issue in dma-buf
> - Added another patch to enforce minimum `rustc` version for powerpc
> V12: https://lore.kernel.org/all/20260421120958.190430-1-mkchauras@gmail.com/
> 
> V11 -> V12:
> - Rebased to mainline (rust/Makefile conflict resolved)
> V11: https://lore.kernel.org/all/20260417152253.2312961-1-mkchauras@gmail.com/
> 
> V10 -> V11:
> - Updated `rust/Makefile`
> - Not all libraries are move to `rust/host` directory now. Only
>   proc_macro2, quote and syn are moved
> - Special handling for pin init is added. Details in commit
> - Removed mkdir for `rust/host`, this is now handled by toolchain.
> V10: https://lore.kernel.org/all/20260406200149.3727922-1-mkchauras@gmail.com/
> 
> V9 -> V10:
> - rust/Makefile updated with review comments from Miguel
> - Patch 1/4 updated with commit message and subject
> V9: https://lore.kernel.org/all/20260404121610.1956528-1-mkchauras@gmail.com/
> 
> V8 -> V9:
> - rust/Makefile updated with a directory instead of abspath
> V8: https://lore.kernel.org/all/20260403145308.1042622-1-mkchauras@gmail.com/
> 
> V7 -> V8:
> - rust/Makefile updated to separate host libraries from target
> V7: https://lore.kernel.org/all/20260329160254.2592207-1-mkchauras@gmail.com/
> 
> Changelog:
> V6 -> V7:
> - Documentation removed as powerpc is still under development
> - Added a fix for race condition in rust/Makefile
> V6: https://lore.kernel.org/all/20260210090023.2587534-1-mkchauras@gmail.com
> 
> V5 -> V6:
> - Added a missing Tested by from Venkat which got missed since V3
> - Support is marked as Maintained instead of experimental
> V5: https://lore.kernel.org/all/20260210053756.2088302-1-mkchauras@gmail.com
> 
> V4 -> V5:
> - Removed a nested ifdef from PPC64 for Little endian toolchain
> V4: https://lore.kernel.org/all/20260209105456.1551677-1-mkchauras@gmail.com
> 
> V3 -> V4:
> - Co-developed-by header added in patch 1
> V3: https://lore.kernel.org/all/20260205180429.3280657-1-mkchauras@gmail.com
> 
> V2 -> V3:
> - Splited HAVE_RUST in 2 lines
> - BINDGEN_TARGET_powerpc initialized before assigning the same to
>   BINDGEN_TARGET
> V2: https://lore.kernel.org/all/20260204210125.613350-1-mkchauras@gmail.com
> 
> V1 -> V2:
> - jump label fix for rust has been moved to a separate patch
> - PPC32 support has been taken
> - rust support has been marked experimental
> - target.json dependency has been removed
> - HAVE_RUST now depends on CPU_LITTLE_ENDIAN for PPC64
> V1: https://lore.kernel.org/all/20260204042417.83903-1-mkchauras@gmail.com 
> 
> Link Mauve (2):
>   rust: Make __udivdi3() and __umoddi3() panic
>   rust: Add PowerPC support
> 
> Mukesh Kumar Chaurasiya (IBM) (6):
>   powerpc/syscall: Fix syscall skip handling for seccomp and ptrace
>   rust: Fix "multiple candidates for rmeta dependency core" error
>   dma-resv: Fix undefined symbol when CONFIG_DMA_SHARED_BUFFER is
>     disabled
>   powerpc/jump_label: adjust inline asm to be consistent
>   rust/powerpc: Set min rustc version for powerpc
>   powerpc: Enable Rust for ppc64le
> 
>  arch/powerpc/Kconfig                   |  2 +
>  arch/powerpc/Makefile                  |  7 ++++
>  arch/powerpc/include/asm/jump_label.h  | 23 ++++++-----
>  arch/powerpc/include/asm/ptrace.h      | 22 +++++++++-
>  arch/powerpc/include/asm/syscall.h     |  6 +++
>  arch/powerpc/include/uapi/asm/ptrace.h |  6 ++-
>  arch/powerpc/kernel/ptrace/ptrace.c    |  2 +
>  arch/powerpc/kernel/syscall.c          | 18 +++++++++
>  rust/Makefile                          | 56 +++++++++++++++++---------
>  rust/compiler_builtins.rs              |  6 +++
>  rust/helpers/helpers.c                 |  2 +
>  scripts/min-tool-version.sh            |  2 +
>  12 files changed, 119 insertions(+), 33 deletions(-)
> 
> -- 
> 2.55.0
> 

Please ignore this.

Regards,
Mukesh