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

[Xiongwei Song]

On Sat, Aug 7, 2021 at 2:57 PM Christophe Leroy
<christophe.leroy@xxxxxxxxxx> wrote:
>
>
>
> Le 07/08/2021 à 03:02, 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.
> >
> > Signed-off-by: Xiongwei Song <sxwjean@xxxxxxxxx>
> > ---
> >   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

>
> >       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");
> >