Messages in this thread |  | | Subject | Re: [RFC PATCH 1/4] powerpc: Optimize register usage for esr register | From | Christophe Leroy <> | Date | Thu, 5 Aug 2021 12:06:15 +0200 |
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Le 26/07/2021 à 16:30, sxwjean@me.com a écrit : > 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.
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@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"); >
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