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powerpc/code-patching: Use WARN_ON and fix check in poking_init

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BUG_ON() when failing to initialise the code patching window is
unnecessary, and use of BUG_ON is discouraged. We don't set
poking_init_done in this case, so failure to init the boot CPU will
result in a strict RWX error when a following patch_instruction uses
raw_patch_instruction. If it only fails for later CPUs, they won't be
onlined in the first place.

The return value of cpuhp_setup_state() is also >= 0 on success,
so check for < 0.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221109045112.187069-3-bgray@linux.ibm.com
This commit is contained in:
Benjamin Gray 2022-11-09 15:51:05 +11:00 committed by Michael Ellerman
parent 3671f4ebe3
commit 071c95c1ac
1 changed files with 9 additions and 8 deletions
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17
arch/powerpc/lib/code-patching.c
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@ -81,16 +81,17 @@ static int text_area_cpu_down(unsigned int cpu)
static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done);
/*
* Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and
* we judge it as being preferable to a kernel that will crash later when
* someone tries to use patch_instruction().
*/
void __init poking_init(void)
{
BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
"powerpc/text_poke:online", text_area_cpu_up,
text_area_cpu_down));
int ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
"powerpc/text_poke:online",
text_area_cpu_up,
text_area_cpu_down);
/* cpuhp_setup_state returns >= 0 on success */
if (WARN_ON(ret < 0))
return;
static_branch_enable(&poking_init_done);
}