Commit 3241f260 authored by Benjamin Gray's avatar Benjamin Gray Committed by Michael Ellerman
Browse files

powerpc/watchpoint: Disable pagefaults when getting user instruction 



This is called in an atomic context, so is not allowed to sleep if a
user page needs to be faulted in and has nowhere it can be deferred to.
The pagefault_disabled() function is documented as preventing user
access methods from sleeping.

In practice the page will be mapped in nearly always because we are
reading the instruction that just triggered the watchpoint trap.

Signed-off-by: default avatarBenjamin Gray <bgray@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230829063457.54157-3-bgray@linux.ibm.com
parent cc879ab3

arch/powerpc/kernel/hw_breakpoint_constraints.c

+6 −1
Original line number Diff line number Diff line
@@ -131,8 +131,13 @@ void wp_get_instr_detail(struct pt_regs *regs, ppc_inst_t *instr, 
			 int *type, int *size, unsigned long *ea)

{

	struct instruction_op op;

	int err;



	if (__get_user_instr(*instr, (void __user *)regs->nip))

	pagefault_disable();

	err = __get_user_instr(*instr, (void __user *)regs->nip);

	pagefault_enable();



	if (err)

		return;



	analyse_instr(&op, regs, *instr);