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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: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230829063457.54157-3-bgray@linux.ibm.com
This commit is contained in:
Benjamin Gray 2023-08-29 16:34:56 +10:00 committed by Michael Ellerman
parent cc879ab3ce
commit 3241f260eb
1 changed files with 6 additions and 1 deletions
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7
arch/powerpc/kernel/hw_breakpoint_constraints.c
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@ -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);