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powerpc: Make cpu_spec __ro_after_init

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The cpu_spec is a struct holding various information about the CPU the
kernel is executing on. It's populated early in boot and must not change
after that.

In particular the cpu_features and mmu_features hold the set of
discovered CPU/MMU features and are used to set static keys for each
feature, and do binary patching of assembly. So any change to the
cpu_features/mmu_features later in boot will not be reflected in
the state of the static keys or patched code.

There is already logic to check that cpu_features/mmu_features don't
change, see check_features() in feature-fixups.c.

But as another layer of protection the entire cpu_spec should be read
only after init, annotate it as such.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231025012452.1985680-1-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2023-10-25 12:24:52 +11:00
parent 183bc0c640
commit 98eb30fe4c
1 changed files with 2 additions and 2 deletions
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4
arch/powerpc/kernel/cputable.c
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@ -20,9 +20,9 @@
#include <asm/setup.h>
#include <asm/cpu_setup.h>
static struct cpu_spec the_cpu_spec __read_mostly;
static struct cpu_spec the_cpu_spec __ro_after_init;
struct cpu_spec* cur_cpu_spec __read_mostly = NULL;
struct cpu_spec *cur_cpu_spec __ro_after_init = NULL;
EXPORT_SYMBOL(cur_cpu_spec);
/* The platform string corresponding to the real PVR */