linux-kernel - [PATCH] arch: tile: kernel: kgdb.c: Use memcpy() instead of pointer copy one by one

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Message-ID: <5454DD70.6060004@gmail.com>
Date:	Sat, 01 Nov 2014 21:17:36 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	metcalf@...era.com
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] arch: tile: kernel: kgdb.c: Use memcpy() instead of pointer
 copy one by one

Not only memcpy() is faster than pointer copy, but also let code more
clearer and simple, which can avoid compiling warning (the original
implementation copy registers by exceeding member array border).

The related warning (with allmodconfig under tile):

    CC      arch/tile/kernel/kgdb.o
  arch/tile/kernel/kgdb.c: In function 'sleeping_thread_to_gdb_regs':
  arch/tile/kernel/kgdb.c:140:31: warning: iteration 53u invokes undefined behavior [-Waggressive-loop-optimizations]
     *(ptr++) = thread_regs->regs[reg];
                                 ^
  arch/tile/kernel/kgdb.c:139:2: note: containing loop
    for (reg = 0; reg <= TREG_LAST_GPR; reg++)
    ^

Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
---
 arch/tile/kernel/kgdb.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/tile/kernel/kgdb.c b/arch/tile/kernel/kgdb.c
index 4cd8838..ff5335a 100644
--- a/arch/tile/kernel/kgdb.c
+++ b/arch/tile/kernel/kgdb.c
@@ -125,9 +125,7 @@ int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 void
 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
 {
-	int reg;
 	struct pt_regs *thread_regs;
-	unsigned long *ptr = gdb_regs;
 
 	if (task == NULL)
 		return;
@@ -136,9 +134,7 @@ sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
 	memset(gdb_regs, 0, NUMREGBYTES);
 
 	thread_regs = task_pt_regs(task);
-	for (reg = 0; reg <= TREG_LAST_GPR; reg++)
-		*(ptr++) = thread_regs->regs[reg];
-
+	memcpy(gdb_regs, thread_regs, TREG_LAST_GPR * sizeof(unsigned long));
 	gdb_regs[TILEGX_PC_REGNUM] = thread_regs->pc;
 	gdb_regs[TILEGX_FAULTNUM_REGNUM] = thread_regs->faultnum;
 }
-- 
1.9.3
--
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