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powerpc/mm: Overhaul handling of bad page faults

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A bad page fault is when the HW signals an error such as a bad
copy/paste, an AMO error, or some other type of error that will
not be fixed by updating the PTE.

Use a helper page_fault_is_bad() to check for bad page faults thus
removing the per-processor family open-coding in __do_page_fault()
and trigger a SIGBUS rather than a SIGSEGV which is more appropriate.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2017-07-19 14:49:31 +10:00 committed by Michael Ellerman
parent e6c8290a89
commit f3d96e698e
1 changed files with 14 additions and 18 deletions
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32
arch/powerpc/mm/fault.c
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@ -188,8 +188,16 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
*/
#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
#define page_fault_is_write(__err) ((__err) & ESR_DST)
#define page_fault_is_bad(__err) (0)
#else
#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
#if defined(CONFIG_8xx)
#define page_fault_is_bad(__err) ((__err) & 0x10000000)
#elif defined(CONFIG_PPC64)
#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
#else
#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
#endif
#endif
/*
@ -237,25 +245,13 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
if (unlikely(debugger_fault_handler(regs)))
goto bail;
#if defined(CONFIG_6xx)
if (error_code & 0x95700000) {
/* an error such as lwarx to I/O controller space,
address matching DABR, eciwx, etc. */
code = SEGV_ACCERR;
goto bad_area_nosemaphore;
if (unlikely(page_fault_is_bad(error_code))) {
if (is_user)
_exception(SIGBUS, regs, BUS_OBJERR, address);
else
rc = SIGBUS;
goto bail;
}
#endif /* CONFIG_6xx */
#if defined(CONFIG_8xx)
/* The MPC8xx seems to always set 0x80000000, which is
* "undefined". Of those that can be set, this is the only
* one which seems bad.
*/
if (error_code & 0x10000000) {
/* Guarded storage error. */
code = SEGV_ACCERR;
goto bad_area_nosemaphore;
}
#endif /* CONFIG_8xx */
/*
* The kernel should never take an execute fault nor should it