linux-kernel - [PATCH v2 3/4] powerpc: Optimize register usage for dear register

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Date:   Sat,  7 Aug 2021 09:02:38 +0800
From:   sxwjean@...com
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     oleg@...hat.com, mpe@...erman.id.au, benh@...nel.crashing.org,
        paulus@...ba.org, christophe.leroy@...roup.eu, npiggin@...il.com,
        ravi.bangoria@...ux.ibm.com, aneesh.kumar@...ux.ibm.com,
        efremov@...ux.com, linux-kernel@...r.kernel.org,
        Xiongwei Song <sxwjean@...il.com>
Subject: [PATCH v2 3/4] powerpc: Optimize register usage for dear register

From: Xiongwei Song <sxwjean@...il.com>

Create an anonymous union for dar and dear regsiters, we can reference
dear to get the effective address when CONFIG_4xx=y or CONFIG_BOOKE=y.
Otherwise, reference dar. This makes code more clear.

Signed-off-by: Xiongwei Song <sxwjean@...il.com>
---
 arch/powerpc/include/asm/ptrace.h   | 5 ++++-
 arch/powerpc/kernel/process.c       | 2 +-
 arch/powerpc/kernel/ptrace/ptrace.c | 2 ++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index c252d04b1206..fa725e3238c2 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -43,7 +43,10 @@ struct pt_regs
 			unsigned long mq;
 #endif
 			unsigned long trap;
-			unsigned long dar;
+			union {
+				unsigned long dar;
+				unsigned long dear;
+			};
 			union {
 				unsigned long dsisr;
 				unsigned long esr;
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index f74af8f9133c..50436b52c213 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1499,7 +1499,7 @@ static void __show_regs(struct pt_regs *regs)
 	    trap == INTERRUPT_DATA_STORAGE ||
 	    trap == INTERRUPT_ALIGNMENT) {
 		if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
-			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->esr);
+			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dear, regs->esr);
 		else
 			pr_cont("DAR: "REG" DSISR: %08lx ", regs->dar, regs->dsisr);
 	}
diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
index a222fd4d6334..7c7093c17c45 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -373,6 +373,8 @@ void __init pt_regs_check(void)
 		     offsetof(struct user_pt_regs, trap));
 	BUILD_BUG_ON(offsetof(struct pt_regs, dar) !=
 		     offsetof(struct user_pt_regs, dar));
+	BUILD_BUG_ON(offsetof(struct pt_regs, dear) !=
+		     offsetof(struct user_pt_regs, dar));
 	BUILD_BUG_ON(offsetof(struct pt_regs, dsisr) !=
 		     offsetof(struct user_pt_regs, dsisr));
 	BUILD_BUG_ON(offsetof(struct pt_regs, esr) !=
-- 
2.30.2