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| author | Will Deacon <will.deacon@arm.com> | 2017-11-14 14:38:19 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2017-12-11 13:41:06 +0000 |
| commit | ea1e3de85e94d711f63437c04624aa0e8de5c8b3 (patch) | |
| tree | f390c46a0ddda1975269041456090a1f09e1ba35 /arch/arm64/kernel/entry.S | |
| parent | 18011eac28c7cb31c87b86b7d0e5b01894405c7f (diff) | |
| download | talos-obmc-linux-ea1e3de85e94d711f63437c04624aa0e8de5c8b3.tar.gz talos-obmc-linux-ea1e3de85e94d711f63437c04624aa0e8de5c8b3.zip | |
arm64: entry: Add fake CPU feature for unmapping the kernel at EL0
Allow explicit disabling of the entry trampoline on the kernel command
line (kpti=off) by adding a fake CPU feature (ARM64_UNMAP_KERNEL_AT_EL0)
that can be used to toggle the alternative sequences in our entry code and
avoid use of the trampoline altogether if desired. This also allows us to
make use of a static key in arm64_kernel_unmapped_at_el0().
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ce56592b5f70..5d51bdbb2131 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -74,6 +74,7 @@ .macro kernel_ventry, el, label, regsize = 64 .align 7 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +alternative_if ARM64_UNMAP_KERNEL_AT_EL0 .if \el == 0 .if \regsize == 64 mrs x30, tpidrro_el0 @@ -82,6 +83,7 @@ mov x30, xzr .endif .endif +alternative_else_nop_endif #endif sub sp, sp, #S_FRAME_SIZE @@ -323,10 +325,9 @@ alternative_else_nop_endif ldr lr, [sp, #S_LR] add sp, sp, #S_FRAME_SIZE // restore sp -#ifndef CONFIG_UNMAP_KERNEL_AT_EL0 - eret -#else .if \el == 0 +alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 bne 4f msr far_el1, x30 tramp_alias x30, tramp_exit_native @@ -334,10 +335,10 @@ alternative_else_nop_endif 4: tramp_alias x30, tramp_exit_compat br x30 +#endif .else eret .endif -#endif .endm .macro irq_stack_entry |
