Re: [PATCH v7 11/16] ARM: LPAE: Add fault handling support

From: Russell King - ARM Linux
Date: Sun Oct 23 2011 - 07:58:10 EST

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On Wed, Aug 10, 2011 at 04:03:34PM +0100, Catalin Marinas wrote:
> diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
> index be7c638..f0bf61a 100644
> --- a/arch/arm/mm/alignment.c
> +++ b/arch/arm/mm/alignment.c
> @@ -909,6 +909,12 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> return 0;
> }
>
> +#ifdef CONFIG_ARM_LPAE
> +#define ALIGNMENT_FAULT 33
> +#else
> +#define ALIGNMENT_FAULT 1
> +#endif

Probably makes sense to move this into a header, along with the other
fault codes, other FSR bits and fsr_fs().

> +
> /*
> * This needs to be done after sysctl_init, otherwise sys/ will be
> * overwritten. Actually, this shouldn't be in sys/ at all since
> @@ -942,7 +948,7 @@ static int __init alignment_init(void)
> ai_usermode = UM_FIXUP;
> }
>
> - hook_fault_code(1, do_alignment, SIGBUS, BUS_ADRALN,
> + hook_fault_code(ALIGNMENT_FAULT, do_alignment, SIGBUS, BUS_ADRALN,
> "alignment exception");
>
> /*
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index 3b5ea68..91d1768 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -33,10 +33,15 @@
> #define FSR_WRITE (1 << 11)
> #define FSR_FS4 (1 << 10)
> #define FSR_FS3_0 (15)
> +#define FSR_FS5_0 (0x3f)
>
> static inline int fsr_fs(unsigned int fsr)
> {
> +#ifdef CONFIG_ARM_LPAE
> + return fsr & FSR_FS5_0;
> +#else
> return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6;
> +#endif
> }
>
> #ifdef CONFIG_MMU
> @@ -122,8 +127,10 @@ void show_pte(struct mm_struct *mm, unsigned long addr)
>
> pte = pte_offset_map(pmd, addr);
> printk(", *pte=%08llx", (long long)pte_val(*pte));
> +#ifndef CONFIG_ARM_LPAE
> printk(", *ppte=%08llx",
> (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
> +#endif
> pte_unmap(pte);
> } while(0);
>
> @@ -440,6 +447,12 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
> pmd = pmd_offset(pud, addr);
> pmd_k = pmd_offset(pud_k, addr);
>
> +#ifdef CONFIG_ARM_LPAE
> + /*
> + * Only one hardware entry per PMD with LPAE.
> + */
> + index = 0;
> +#else
> /*
> * On ARM one Linux PGD entry contains two hardware entries (see page
> * tables layout in pgtable.h). We normally guarantee that we always
> @@ -449,6 +462,7 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
> * for the first of pair.
> */
> index = (addr >> SECTION_SHIFT) & 1;
> +#endif
> if (pmd_none(pmd_k[index]))
> goto bad_area;
>
> @@ -494,6 +508,72 @@ static struct fsr_info {
> int code;
> const char *name;
> } fsr_info[] = {
> +#ifdef CONFIG_ARM_LPAE
> + { do_bad, SIGBUS, 0, "unknown 0" },
> + { do_bad, SIGBUS, 0, "unknown 1" },
> + { do_bad, SIGBUS, 0, "unknown 2" },
> + { do_bad, SIGBUS, 0, "unknown 3" },
> + { do_bad, SIGBUS, 0, "reserved translation fault" },
> + { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" },
> + { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" },
> + { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" },
> + { do_bad, SIGBUS, 0, "reserved access flag fault" },
> + { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" },
> + { do_bad, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" },
> + { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" },
> + { do_bad, SIGBUS, 0, "reserved permission fault" },
> + { do_bad, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" },
> + { do_sect_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" },
> + { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" },
> + { do_bad, SIGBUS, 0, "synchronous external abort" },
> + { do_bad, SIGBUS, 0, "asynchronous external abort" },
> + { do_bad, SIGBUS, 0, "unknown 18" },
> + { do_bad, SIGBUS, 0, "unknown 19" },
> + { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
> + { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
> + { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
> + { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
> + { do_bad, SIGBUS, 0, "synchronous parity error" },
> + { do_bad, SIGBUS, 0, "asynchronous parity error" },
> + { do_bad, SIGBUS, 0, "unknown 26" },
> + { do_bad, SIGBUS, 0, "unknown 27" },
> + { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
> + { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
> + { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
> + { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" },
> + { do_bad, SIGBUS, 0, "unknown 32" },
> + { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" },
> + { do_bad, SIGBUS, 0, "debug event" },
> + { do_bad, SIGBUS, 0, "unknown 35" },
> + { do_bad, SIGBUS, 0, "unknown 36" },
> + { do_bad, SIGBUS, 0, "unknown 37" },
> + { do_bad, SIGBUS, 0, "unknown 38" },
> + { do_bad, SIGBUS, 0, "unknown 39" },
> + { do_bad, SIGBUS, 0, "unknown 40" },
> + { do_bad, SIGBUS, 0, "unknown 41" },
> + { do_bad, SIGBUS, 0, "unknown 42" },
> + { do_bad, SIGBUS, 0, "unknown 43" },
> + { do_bad, SIGBUS, 0, "unknown 44" },
> + { do_bad, SIGBUS, 0, "unknown 45" },
> + { do_bad, SIGBUS, 0, "unknown 46" },
> + { do_bad, SIGBUS, 0, "unknown 47" },
> + { do_bad, SIGBUS, 0, "unknown 48" },
> + { do_bad, SIGBUS, 0, "unknown 49" },
> + { do_bad, SIGBUS, 0, "unknown 50" },
> + { do_bad, SIGBUS, 0, "unknown 51" },
> + { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" },
> + { do_bad, SIGBUS, 0, "unknown 53" },
> + { do_bad, SIGBUS, 0, "unknown 54" },
> + { do_bad, SIGBUS, 0, "unknown 55" },
> + { do_bad, SIGBUS, 0, "unknown 56" },
> + { do_bad, SIGBUS, 0, "unknown 57" },
> + { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" },
> + { do_bad, SIGBUS, 0, "unknown 59" },
> + { do_bad, SIGBUS, 0, "unknown 60" },
> + { do_bad, SIGBUS, 0, "unknown 61" },
> + { do_bad, SIGBUS, 0, "unknown 62" },
> + { do_bad, SIGBUS, 0, "unknown 63" },
> +#else /* !CONFIG_ARM_LPAE */
> /*
> * The following are the standard ARMv3 and ARMv4 aborts. ARMv5
> * defines these to be "precise" aborts.
> @@ -535,6 +615,7 @@ static struct fsr_info {
> { do_bad, SIGBUS, 0, "unknown 29" },
> { do_bad, SIGBUS, 0, "unknown 30" },
> { do_bad, SIGBUS, 0, "unknown 31" }
> +#endif /* CONFIG_ARM_LPAE */

Can't we do better than this?

> };
>
> void __init
> @@ -573,6 +654,9 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> }
>
>
> +#ifdef CONFIG_ARM_LPAE
> +#define ifsr_info fsr_info
> +#else /* !CONFIG_ARM_LPAE */
> static struct fsr_info ifsr_info[] = {
> { do_bad, SIGBUS, 0, "unknown 0" },
> { do_bad, SIGBUS, 0, "unknown 1" },
> @@ -607,6 +691,7 @@ static struct fsr_info ifsr_info[] = {
> { do_bad, SIGBUS, 0, "unknown 30" },
> { do_bad, SIGBUS, 0, "unknown 31" },
> };
> +#endif /* CONFIG_ARM_LPAE */
>
> void __init
> hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
> @@ -642,6 +727,7 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
>
> static int __init exceptions_init(void)
> {
> +#ifndef CONFIG_ARM_LPAE
> if (cpu_architecture() >= CPU_ARCH_ARMv6) {
> hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
> "I-cache maintenance fault");
> @@ -657,6 +743,7 @@ static int __init exceptions_init(void)
> hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
> "section access flag fault");
> }
> +#endif
>
> return 0;
> }

Do we even need exceptions_init() at all for LPAE? If not, can't we
avoid the whole of this including the useless init call.
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