diff options
| author | Mark Brown <broonie@kernel.org> | 2022-11-23 18:02:08 +0000 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2022-11-25 12:17:52 +0000 |
| commit | a8bf2fc43fc63c0bd38b45c9a9616d43b683585d (patch) | |
| tree | 1b441bb55fc74843b02d02517879236f1a87ee75 /arch/arm64/include | |
| parent | 32d495b0c3305546f4773b9aafcd4e90188ddb9e (diff) | |
arm64/kpti: Move DAIF masking to C code
We really don't want to take an exception while replacing TTBR1 so we mask
DAIF during the actual update. Currently this is done in the assembly
function idmap_cpu_replace_ttbr1() but it could equally be done in the only
caller of that function, cpu_replace_ttbr1(). This simplifies the assembly
code slightly and means that when working with the code around masking DAIF
flags there is one less piece of assembly code which needs to be considered.
While we're at it add a comment which makes explicit why we are masking
DAIF in this code.
There should be no functional effect.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221123180209.634650-2-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/mmu_context.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index d3f8b5df0c1f..72dbd6400549 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -18,6 +18,7 @@ #include <asm/cacheflush.h> #include <asm/cpufeature.h> +#include <asm/daifflags.h> #include <asm/proc-fns.h> #include <asm-generic/mm_hooks.h> #include <asm/cputype.h> @@ -152,6 +153,7 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap) typedef void (ttbr_replace_func)(phys_addr_t); extern ttbr_replace_func idmap_cpu_replace_ttbr1; ttbr_replace_func *replace_phys; + unsigned long daif; /* phys_to_ttbr() zeros lower 2 bits of ttbr with 52-bit PA */ phys_addr_t ttbr1 = phys_to_ttbr(virt_to_phys(pgdp)); @@ -171,7 +173,15 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp, pgd_t *idmap) replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1); __cpu_install_idmap(idmap); + + /* + * We really don't want to take *any* exceptions while TTBR1 is + * in the process of being replaced so mask everything. + */ + daif = local_daif_save(); replace_phys(ttbr1); + local_daif_restore(daif); + cpu_uninstall_idmap(); } |