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powerpc/32s: Allow disabling KUEP at boot time

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PPC64 uses MMU features to enable/disable KUEP at boot time.
But feature fixups are applied way too early on PPC32.

Now that all KUEP related actions are in C following the
conversion of KUEP initial setup and context switch in C,
static branches can be used to enable/disable KUEP.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7745a2c3a08ec46302920a3f48d1cb9b5469dbbb.1622708530.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-06-03 08:41:42 +00:00 committed by Michael Ellerman
parent 86f46f3432
commit 50d2f104cd
2 changed files with 12 additions and 5 deletions
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6
arch/powerpc/include/asm/book3s/32/kup.h
View File

@ -7,6 +7,10 @@
#ifndef __ASSEMBLY__
#include <linux/jump_label.h>
extern struct static_key_false disable_kuep_key;
static __always_inline bool kuap_is_disabled(void)
{
return !IS_ENABLED(CONFIG_PPC_KUAP);
@ -14,7 +18,7 @@ static __always_inline bool kuap_is_disabled(void)
static __always_inline bool kuep_is_disabled(void)
{
return !IS_ENABLED(CONFIG_PPC_KUEP);
return !IS_ENABLED(CONFIG_PPC_KUEP) || static_branch_unlikely(&disable_kuep_key);
}
static inline void kuep_lock(void)

11
arch/powerpc/mm/book3s32/kuep.c
View File

@ -3,15 +3,18 @@
#include <asm/kup.h>
#include <asm/smp.h>
struct static_key_false disable_kuep_key;
void __init setup_kuep(bool disabled)
{
kuep_lock();
if (!disabled)
kuep_lock();
if (smp_processor_id() != boot_cpuid)
return;
pr_info("Activating Kernel Userspace Execution Prevention\n");
if (disabled)
pr_warn("KUEP cannot be disabled yet on 6xx when compiled in\n");
static_branch_enable(&disable_kuep_key);
else
pr_info("Activating Kernel Userspace Execution Prevention\n");
}