[PATCH v4 5/8] powerpc: add exit_flags field in pt_regs

Mukesh Kumar Chaurasiya
2026-01-23T07:40:57Z

From: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>

Add a new field `exit_flags` in the pt_regs structure. This field will hold
the flags set during interrupt or syscall execution that are required during
exit to user mode.

Specifically, the `TIF_RESTOREALL` flag, stored in this field, helps the
exit routine determine if any NVGPRs were modified and need to be restored
before returning to userspace.

This addition ensures a clean and architecture-specific mechanism to track
per-syscall or per-interrupt state transitions related to register restore.

Changes:
- Add `exit_flags` and `__pt_regs_pad` to maintain 16-byte stack alignment
- Update asm-offsets.c and ptrace.c for offset and validation
- Update PT_* constants in uapi header to reflect the new layout

Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
---
arch/powerpc/include/asm/ptrace.h | 3 +++
arch/powerpc/include/uapi/asm/ptrace.h | 14 +++++++++-----
arch/powerpc/kernel/ptrace/ptrace.c | 1 +
3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 94aa1de2b06e..2e741ea57b80 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -53,6 +53,9 @@ struct pt_regs
unsigned long esr;
};
unsigned long result;
+ unsigned long exit_flags;
+ /* Maintain 16 byte interrupt stack alignment */
+ unsigned long __pt_regs_pad[3];
};
};
#if defined(CONFIG_PPC64) || defined(CONFIG_PPC_KUAP)
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index 01e630149d48..a393b7f2760a 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -55,6 +55,8 @@ struct pt_regs
unsigned long dar; /* Fault registers */
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 */
};

#endif /* __ASSEMBLER__ */
@@ -114,10 +116,12 @@ struct pt_regs
#define PT_DAR 41
#define PT_DSISR 42
#define PT_RESULT 43
-#define PT_DSCR 44
-#define PT_REGS_COUNT 44
+#define PT_EXIT_FLAGS 44
+#define PT_PAD 47 /* 3 times */
+#define PT_DSCR 48
+#define PT_REGS_COUNT 48

-#define PT_FPR0 48 /* each FP reg occupies 2 slots in this space */
+#define PT_FPR0 (PT_REGS_COUNT + 4) /* each FP reg occupies 2 slots in this space */

#ifndef __powerpc64__

@@ -129,7 +133,7 @@ struct pt_regs
#define PT_FPSCR (PT_FPR0 + 32) /* each FP reg occupies 1 slot in 64-bit space */

-#define PT_VR0 82 /* each Vector reg occupies 2 slots in 64-bit */
+#define PT_VR0 (PT_FPSCR + 2) /* <82> each Vector reg occupies 2 slots in 64-bit */
#define PT_VSCR (PT_VR0 + 32*2 + 1)
#define PT_VRSAVE (PT_VR0 + 33*2)

@@ -137,7 +141,7 @@ struct pt_regs
/*
* Only store first 32 VSRs here. The second 32 VSRs in VR0-31
*/
-#define PT_VSR0 150 /* each VSR reg occupies 2 slots in 64-bit */
+#define PT_VSR0 (PT_VRSAVE + 2) /* each VSR reg occupies 2 slots in 64-bit */
#define PT_VSR31 (PT_VSR0 + 2*31)
#endif /* __powerpc64__ */

diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
index c6997df63287..2134b6d155ff 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -432,6 +432,7 @@ void __init pt_regs_check(void)
CHECK_REG(PT_DAR, dar);
CHECK_REG(PT_DSISR, dsisr);
CHECK_REG(PT_RESULT, result);
+ CHECK_REG(PT_EXIT_FLAGS, exit_flags);
#undef CHECK_REG

BUILD_BUG_ON(PT_REGS_COUNT != sizeof(struct user_pt_regs) / sizeof(unsigned long));
--
2.52.0