linux-kernel - [PATCH v2] MIPS: Fix MAX_REG_OFFSET and remove zero-length struct member

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Message-ID: <20250417174712.69292-2-thorsten.blum@linux.dev>
Date: Thu, 17 Apr 2025 19:47:13 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Oleg Nesterov <oleg@...hat.com>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: "Maciej W. Rozycki" <macro@...am.me.uk>,
	Thorsten Blum <thorsten.blum@...ux.dev>,
	linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] MIPS: Fix MAX_REG_OFFSET and remove zero-length struct member

Remove the unnecessary zero-length struct member '__last' and fix
MAX_REG_OFFSET to point to the last register in 'pt_regs'.

Fixes: 40e084a506eba ("MIPS: Add uprobes support.")
Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
Compile-tested only.

Changes in v2:
- Fix MAX_REG_OFFSET as suggested by Maciej (thanks!)
- Link to v1: https://lore.kernel.org/lkml/20250411090032.7844-1-thorsten.blum@linux.dev/
---
 arch/mips/include/asm/ptrace.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
index 85fa9962266a..23acad11ac8e 100644
--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -48,7 +48,6 @@ struct pt_regs {
 	unsigned long long mpl[6];        /* MTM{0-5} */
 	unsigned long long mtp[6];        /* MTP{0-5} */
 #endif
-	unsigned long __last[0];
 } __aligned(8);
 
 static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
@@ -65,7 +64,11 @@ static inline void instruction_pointer_set(struct pt_regs *regs,
 
 /* Query offset/name of register from its name/offset */
 extern int regs_query_register_offset(const char *name);
-#define MAX_REG_OFFSET (offsetof(struct pt_regs, __last))
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+#define MAX_REG_OFFSET offsetof(struct pt_regs, mtp[5])
+#else
+#define MAX_REG_OFFSET offsetof(struct pt_regs, cp0_epc)
+#endif
 
 /**
  * regs_get_register() - get register value from its offset
-- 
2.49.0