Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults. | Date | Mon, 17 Dec 2018 23:28:19 +1100 |
| |
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > index 01b9bcc7fa85..3398291f4785 100644 > --- a/arch/powerpc/mm/fault.c > +++ b/arch/powerpc/mm/fault.c > @@ -636,21 +636,24 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) > switch (TRAP(regs)) { > case 0x300: > case 0x380: > - printk(KERN_ALERT "Unable to handle kernel paging request for " > - "data at address 0x%08lx\n", regs->dar); > + if (regs->dar < PAGE_SIZE) > + pr_alert("BUG: Kernel NULL pointer dereference"); > + else > + pr_alert("BUG: Unable to handle kernel data access"); > + pr_cont(" at 0x%08lx\n", regs->dar);
It's best to avoid pr_cont() as it can lead to interleaving, so I rewrote this as:
pr_alert("BUG: %s at 0x%08lx\n", regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" : "Unable to handle kernel data access", regs->dar);
> break; > case 0x400: > case 0x480: > - printk(KERN_ALERT "Unable to handle kernel paging request for " > - "instruction fetch\n"); > + pr_alert("BUG: Unable to handle kernel instruction fetch%s", > + regs->nip < PAGE_SIZE ? " (NULL pointer ?)\n" : "\n"); I dropped the space here ^
cheers
| |