On Fri, Oct 26, 2018 at 12:00:09AM +0530, Souptick Joarder wrote: > On Thu, Oct 25, 2018 at 11:40 PM Florian Fainelli <f.faine...@gmail.com> > wrote: > > > > Some software such as perf makes unconditional use of the special > > [vectors] page which is only provided when CONFIG_KUSER_HELPERS is > > enabled in the kernel. > > > > Facilitate the debugging of such situations by printing a debug message > > to the kernel log showing the task name and the faulting address. > > > > Suggested-by: Russell King <rmk+ker...@armlinux.org.uk> > > Signed-off-by: Florian Fainelli <f.faine...@gmail.com> > > --- > > arch/arm/mm/fault.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c > > index f4ea4c62c613..f17471fbc1c4 100644 > > --- a/arch/arm/mm/fault.c > > +++ b/arch/arm/mm/fault.c > > @@ -173,6 +173,11 @@ __do_user_fault(struct task_struct *tsk, unsigned long > > addr, > > show_regs(regs); > > } > > #endif > > +#ifndef CONFIG_KUSER_HELPERS > > Just have one doubt, if the condition is "#ifdef CONFIG_KUSER_HELPER" > as commit message suggests the scenario is valid when CONFIG_KUSER_HELPER > is enabled ? No ? > > > + if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000)) > > + printk(KERN_DEBUG "%s: CONFIG_KUSER_HELPERS disabled at > > 0x%08lx\n", > > + tsk->comm, addr); > > +#endif
The idea is to print a message when we get a SEGV _and_ the faulting address is in the vectors page _and_ CONFIG_KUSER_HELPERS is _not_ set (which makes the page inaccessible.) The message points users to enable it and/or why the application has failed. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
