Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write. | Date | Thu, 29 Aug 2019 22:14:38 +1000 |
| |
Christophe Leroy <christophe.leroy@c-s.fr> writes: > DSISR has a bit to tell if the fault is due to a read or a write.
Except some CPUs don't have a DSISR?
Which is why we have page_fault_is_write() that's used in __do_page_fault().
Or is that old cruft?
I see eg. in head_40x.S we pass r5=0 for error code, and we don't set regs->dsisr anywhere AFAICS. So it might just contain some junk.
cheers
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index 8432c281de92..b5047f9b5dec 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault); > void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) > { > const struct exception_table_entry *entry; > + int is_write = page_fault_is_write(regs->dsisr); > > /* Are we prepared to handle this fault? */ > if ((entry = search_exception_tables(regs->nip)) != NULL) { > @@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) > case 0x300: > case 0x380: > case 0xe00: > - pr_alert("BUG: %s at 0x%08lx\n", > + pr_alert("BUG: %s on %s at 0x%08lx\n", > regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" : > - "Unable to handle kernel data access", regs->dar); > + "Unable to handle kernel data access", > + is_write ? "write" : "read", regs->dar);
> break; > case 0x400: > case 0x480: > -- > 2.13.3
| |