| Message ID | 20210726143053.532839-1-sxwjean@me.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [RFC,1/4] powerpc: Optimize register usage for esr register | expand |
| Related | show |
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"); >
On Thu, Aug 5, 2021 at 6:06 PM Christophe Leroy <christophe.leroy@csgroup.eu> wrote: > > > > 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. Why don't we use "esr" as reference manauls mentioned? > > 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); > > + Yes, we can drop this. But it's a bit vague. > 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. We can drop this too. > > > 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. If so, this would make other people more confused. My consideration is to follow what the reference manuals represent. Thank you so much for your comments. Regards, Xiongwei > > > > > > 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"); > >
sxwjean@me.com writes: > 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. > > 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; > + }; I don't mind doing that. > 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 */ > }; But I'm not sure about the use of anonymous unions in UAPI headers. Old compilers don't support them, so there's a risk of breakage. I'd rather we didn't touch the uapi version. > 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); As Christophe said, I don't thinks this is an improvement. It makes the code less readable. If anyone is confused about what is passed to ___do_page_fault() they can either read the comment above it, or look at the definition of pt_regs to see that esr and dsisr share storage. cheers
Le 06/08/2021 à 05:16, Xiongwei Song a écrit : > On Thu, Aug 5, 2021 at 6:06 PM Christophe Leroy > <christophe.leroy@csgroup.eu> wrote: >> >> >> >> 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. > Why don't we use "esr" as reference manauls mentioned? > >> >> 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); >> > + > Yes, we can drop this. But it's a bit vague. > >> 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. > > We can drop this too. >> >> >> 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. > > If so, this would make other people more confused. My consideration is > to follow what the reference > manuals represent. Maybe then we could rename the fields as regs->dsisr_esr and regs->dar_dear That would be more explicit for everyone. The UAPI header however should remain as is because anonymous unions are not supported by old compilers as mentioned by Michael. But nevertheless, there are also situations where was is stored in regs->dsisr is not what we have in DSISR register. For instance on an ISI exception, we store a subset of the content of SRR1 register into regs->dsisr. Christophe
On Fri, Aug 6, 2021 at 2:53 PM Michael Ellerman <mpe@ellerman.id.au> wrote: > > sxwjean@me.com writes: > > 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. > > > > 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; > > + }; > > I don't mind doing that. > > > 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 */ > > }; > > But I'm not sure about the use of anonymous unions in UAPI headers. Old > compilers don't support them, so there's a risk of breakage. > > I'd rather we didn't touch the uapi version. Ok. Will discard the change. > > > > 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); > > As Christophe said, I don't thinks this is an improvement. > > It makes the code less readable. If anyone is confused about what is > passed to ___do_page_fault() they can either read the comment above it, > or look at the definition of pt_regs to see that esr and dsisr share > storage. Ok, thanks a lot. Will send v2. Regards, Xiongwei > > cheers
On Fri, Aug 6, 2021 at 3:32 PM Christophe Leroy <christophe.leroy@csgroup.eu> wrote: > > > > Le 06/08/2021 à 05:16, Xiongwei Song a écrit : > > On Thu, Aug 5, 2021 at 6:06 PM Christophe Leroy > > <christophe.leroy@csgroup.eu> wrote: > >> > >> > >> > >> 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. > > Why don't we use "esr" as reference manauls mentioned? > > > >> > >> 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); > >> > + > > Yes, we can drop this. But it's a bit vague. > > > >> 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. > > > > We can drop this too. > >> > >> > >> 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. > > > > If so, this would make other people more confused. My consideration is > > to follow what the reference > > manuals represent. > > Maybe then we could rename the fields as regs->dsisr_esr and regs->dar_dear I still prefer my method. > > That would be more explicit for everyone. > > The UAPI header however should remain as is because anonymous unions are not supported by old > compilers as mentioned by Michael. Sure. Will update in v2. > > But nevertheless, there are also situations where was is stored in regs->dsisr is not what we have > in DSISR register. For instance on an ISI exception, we store a subset of the content of SRR1 > register into regs->dsisr. Can I think my method has better expansibility here;-)? Let me finish esr and dear first. Thank you for the reminder. Regards, Xiongwei > > Christophe
On Fri, Aug 06, 2021 at 04:53:14PM +1000, Michael Ellerman wrote: > But I'm not sure about the use of anonymous unions in UAPI headers. Old > compilers don't support them, so there's a risk of breakage. More precisely, it exists only since C11, so even with all not-so-ancient compilers it will not work if the user uses (say) -std=c99, which still is popular. > I'd rather we didn't touch the uapi version. Yeah. > > - 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); > > As Christophe said, I don't thinks this is an improvement. > > It makes the code less readable. If anyone is confused about what is > passed to ___do_page_fault() they can either read the comment above it, > or look at the definition of pt_regs to see that esr and dsisr share > storage. Esp. since the affected platforms are legacy, yup. Segher
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");