Re: [PATCH v2 3/4] powerpc: Optimize register usage for dear register

From: Xiongwei Song <redacted>

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 <redacted>
---
  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));