powerpc: Add esr as a synonym for pt_regs.dsisr

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>
[mpe: Reword commit title]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210807010239.416055-2-sxwjean@me.com

arch/powerpc/include/asm/ptrace.h

@@ -44,7 +44,10 @@ struct pt_regs
 #endif
 			unsigned long trap;
 			unsigned long dar;
+			union {
 				unsigned long dsisr;
+				unsigned long esr;
+			};
 			unsigned long result;
 		};
 	};

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);
 	}

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, dsisr));
 	BUILD_BUG_ON(offsetof(struct pt_regs, result) !=
 		     offsetof(struct user_pt_regs, result));
 

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

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");

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");