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powerpc/kernel: Check features don't change after patching 

Early in boot we binary patch some sections of code based on the CPU and
MMU feature bits. But it is a one-time patching, there is no facility
for repatching the code later if the set of features change.

It is a major bug if the set of features changes after we've done the
code patching - so add a check for it.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2016-07-26 22:29:18 +10:00
parent 9e8066f398
commit a28e46f109
1 changed files with 26 additions and 1 deletions
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27
arch/powerpc/lib/feature-fixups.c
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@ -152,10 +152,19 @@ static void do_final_fixups(void)
#endif
}
void apply_feature_fixups(void)
static unsigned long __initdata saved_cpu_features;
static unsigned int __initdata saved_mmu_features;
#ifdef CONFIG_PPC64
static unsigned long __initdata saved_firmware_features;
#endif
void __init apply_feature_fixups(void)
{
struct cpu_spec *spec = *PTRRELOC(&cur_cpu_spec);
*PTRRELOC(&saved_cpu_features) = spec->cpu_features;
*PTRRELOC(&saved_mmu_features) = spec->mmu_features;
/*
* Apply the CPU-specific and firmware specific fixups to kernel text
* (nop out sections not relevant to this CPU or this firmware).
@ -173,12 +182,28 @@ void apply_feature_fixups(void)
PTRRELOC(&__stop___lwsync_fixup));
#ifdef CONFIG_PPC64
saved_firmware_features = powerpc_firmware_features;
do_feature_fixups(powerpc_firmware_features,
&__start___fw_ftr_fixup, &__stop___fw_ftr_fixup);
#endif
do_final_fixups();
}
static int __init check_features(void)
{
WARN(saved_cpu_features != cur_cpu_spec->cpu_features,
"CPU features changed after feature patching!\n");
WARN(saved_mmu_features != cur_cpu_spec->mmu_features,
"MMU features changed after feature patching!\n");
#ifdef CONFIG_PPC64
WARN(saved_firmware_features != powerpc_firmware_features,
"Firmware features changed after feature patching!\n");
#endif
return 0;
}
late_initcall(check_features);
#ifdef CONFIG_FTR_FIXUP_SELFTEST
#define check(x) \