Re: [PATCH v2 1/4] powerpc: Optimize register usage for esr register

On Sat, Aug 7, 2021 at 2:57 PM Christophe Leroy
[off-list ref] wrote:

Le 07/08/2021 à 03:02, sxwjean@me.com a écrit :

quoted

From: Xiongwei Song <redacted>

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 <redacted>
---
  arch/powerpc/include/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/platforms/44x/machine_check.c | 4 ++--
  arch/powerpc/platforms/4xx/machine_check.c | 2 +-
  6 files changed, 11 insertions(+), 6 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/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..a222fd4d6334 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, dsisr));

esr and dsisr are the same, so checking the same thing a second time is pointless.

Hmm...it's better to check if the changes on pt_regs structure is
expected I think.

Regards,
Xiongwei

quoted

      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/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");