Re: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register
From: Christophe Leroy
Date: Thu Aug 05 2021 - 06:06:43 EST
Le 26/07/2021 à 16:30, sxwjean@xxxxxx a écrit :
From: Xiongwei Song <sxwjean@xxxxxxxxx>
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.
I'm not sure it is worth doing that.
What is the point in doing the following when you know that regs->esr and regs->dsisr are exactly
the same:
> - 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);
> +
Or even
> - 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);
Artificially growing the code for that makes no sense to me.
To avoid anbiguity, maybe the best would be to rename regs->dsisr to something like regs->sr , so
that we know it represents the status register, which is DSISR or ESR depending on the platform.
Signed-off-by: Xiongwei Song <sxwjean@xxxxxxxxx>
---
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");