linux-kernel - [PATCH v3 5/8] powerpc: add exit_flags field in pt

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Message-ID: <20251229045416.3193779-6-mkchauras@linux.ibm.com>
Date: Mon, 29 Dec 2025 10:24:13 +0530
From: Mukesh Kumar Chaurasiya <mkchauras@...ux.ibm.com>
To: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        chleroy@...nel.org, oleg@...hat.com, kees@...nel.org,
        luto@...capital.net, wad@...omium.org, mchauras@...ux.ibm.com,
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        peterz@...radead.org, namcao@...utronix.de, tglx@...utronix.de,
        kan.liang@...ux.intel.com, mark.barnett@....com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 5/8] powerpc: add exit_flags field in pt_regs

From: Mukesh Kumar Chaurasiya <mchauras@...ux.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@...ux.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