[PATCH] ARM: mm: Facilitate debugging CONFIG_KUSER_HELPERS disabled

Florian Fainelli
2018-10-25T18:10:28Z

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+kernel@armlinux.org.uk>
Signed-off-by: Florian Fainelli <f.fainelli@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
+ if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
+ printk(KERN_DEBUG "%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
+ tsk->comm, addr);
+#endif

tsk->thread.address = addr;
tsk->thread.error_code = fsr;
--
2.17.1