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From:   sxwjean@me.com
To:     linuxppc-dev@lists.ozlabs.org
Cc:     oleg@redhat.com, mpe@ellerman.id.au, benh@kernel.crashing.org,
        paulus@samba.org, ravi.bangoria@linux.ibm.com,
        christophe.leroy@csgroup.eu, npiggin@gmail.com,
        aneesh.kumar@linux.ibm.com, sandipan@linux.ibm.com,
        efremov@linux.com, peterx@redhat.com, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, Xiongwei Song <sxwjean@gmail.com>
Subject: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register
Date:   Mon, 26 Jul 2021 22:30:50 +0800
Message-Id: <20210726143053.532839-1-sxwjean@me.com>
MIME-Version: 1.0
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From: Xiongwei Song <sxwjean@gmail.com>

Create an anonymous union for dsisr and esr regsiters, we can reference
esr to get the exception detail when CONFIG_4xx=y or CONFIG_BOOKE=y.
Otherwise, reference dsisr. This makes code more clear.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
---
 arch/powerpc/include/asm/ptrace.h          |  5 ++++-
 arch/powerpc/include/uapi/asm/ptrace.h     |  5 ++++-
 arch/powerpc/kernel/process.c              |  2 +-
 arch/powerpc/kernel/ptrace/ptrace.c        |  2 ++
 arch/powerpc/kernel/traps.c                |  2 +-
 arch/powerpc/mm/fault.c                    | 16 ++++++++++++++--
 arch/powerpc/platforms/44x/machine_check.c |  4 ++--
 arch/powerpc/platforms/4xx/machine_check.c |  2 +-
 8 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 3e5d470a6155..c252d04b1206 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -44,7 +44,10 @@ struct pt_regs
 #endif
 			unsigned long trap;
 			unsigned long dar;
-			unsigned long dsisr;
+			union {
+				unsigned long dsisr;
+				unsigned long esr;
+			};
 			unsigned long result;
 		};
 	};
diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index 7004cfea3f5f..e357288b5f34 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -53,7 +53,10 @@ struct pt_regs
 	/* N.B. for critical exceptions on 4xx, the dar and dsisr
 	   fields are overloaded to hold srr0 and srr1. */
 	unsigned long dar;		/* Fault registers */
-	unsigned long dsisr;		/* on 4xx/Book-E used for ESR */
+	union {
+		unsigned long dsisr;		/* on Book-S used for DSISR */
+		unsigned long esr;		/* on 4xx/Book-E used for ESR */
+	};
 	unsigned long result;		/* Result of a system call */
 };
 
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 185beb290580..f74af8f9133c 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->dsisr);
+			pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, 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 0a0a33eb0d28..00789ad2c4a3 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -375,6 +375,8 @@ void __init pt_regs_check(void)
 		     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) !=
+		     offsetof(struct user_pt_regs, esr));
 	BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
 		     offsetof(struct user_pt_regs, result));
 
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index dfbce527c98e..2164f5705a0b 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -562,7 +562,7 @@ static inline int check_io_access(struct pt_regs *regs)
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 /* On 4xx, the reason for the machine check or program exception
    is in the ESR. */
-#define get_reason(regs)	((regs)->dsisr)
+#define get_reason(regs)	((regs)->esr)
 #define REASON_FP		ESR_FP
 #define REASON_ILLEGAL		(ESR_PIL | ESR_PUO)
 #define REASON_PRIVILEGED	ESR_PPR
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index a8d0ce85d39a..62953d4e7c93 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -541,7 +541,11 @@ static __always_inline void __do_page_fault(struct pt_regs *regs)
 {
 	long err;
 
-	err = ___do_page_fault(regs, regs->dar, regs->dsisr);
+	if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
+		err = ___do_page_fault(regs, regs->dar, regs->esr);
+	else
+		err = ___do_page_fault(regs, regs->dar, regs->dsisr);
+
 	if (unlikely(err))
 		bad_page_fault(regs, err);
 }
@@ -567,7 +571,15 @@ NOKPROBE_SYMBOL(hash__do_page_fault);
  */
 static void __bad_page_fault(struct pt_regs *regs, int sig)
 {
-	int is_write = page_fault_is_write(regs->dsisr);
+	unsigned long err_reg;
+	int is_write;
+
+	if (IS_ENABLED(CONFIG_4xx) || IS_ENABLED(CONFIG_BOOKE))
+		err_reg = regs->esr;
+	else
+		err_reg = regs->dsisr;
+
+	is_write = page_fault_is_write(err_reg);
 
 	/* kernel has accessed a bad area */
 
diff --git a/arch/powerpc/platforms/44x/machine_check.c b/arch/powerpc/platforms/44x/machine_check.c
index a5c898bb9bab..5d19daacd78a 100644
--- a/arch/powerpc/platforms/44x/machine_check.c
+++ b/arch/powerpc/platforms/44x/machine_check.c
@@ -11,7 +11,7 @@
 
 int machine_check_440A(struct pt_regs *regs)
 {
-	unsigned long reason = regs->dsisr;
+	unsigned long reason = regs->esr;
 
 	printk("Machine check in kernel mode.\n");
 	if (reason & ESR_IMCP){
@@ -48,7 +48,7 @@ int machine_check_440A(struct pt_regs *regs)
 #ifdef CONFIG_PPC_47x
 int machine_check_47x(struct pt_regs *regs)
 {
-	unsigned long reason = regs->dsisr;
+	unsigned long reason = regs->esr;
 	u32 mcsr;
 
 	printk(KERN_ERR "Machine check in kernel mode.\n");
diff --git a/arch/powerpc/platforms/4xx/machine_check.c b/arch/powerpc/platforms/4xx/machine_check.c
index a71c29892a91..a905da1d6f41 100644
--- a/arch/powerpc/platforms/4xx/machine_check.c
+++ b/arch/powerpc/platforms/4xx/machine_check.c
@@ -10,7 +10,7 @@
 
 int machine_check_4xx(struct pt_regs *regs)
 {
-	unsigned long reason = regs->dsisr;
+	unsigned long reason = regs->esr;
 
 	if (reason & ESR_IMCP) {
 		printk("Instruction");
-- 
2.30.2