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author | Will Deacon <will.deacon@arm.com> | 2017-11-14 14:07:40 +0000 |
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committer | Will Deacon <will.deacon@arm.com> | 2017-12-11 13:40:47 +0000 |
commit | c7b9adaf85f818d747eeff5145eb4095ccd587fb (patch) | |
tree | 9c4bd42693c9f41f676c149e87b74f764b38b3b5 /arch/arm64/kernel/entry.S | |
parent | 9b0de864b5bc298ea53005ad812f3386f81aee9c (diff) | |
download | linux-stable-c7b9adaf85f818d747eeff5145eb4095ccd587fb.tar.gz linux-stable-c7b9adaf85f818d747eeff5145eb4095ccd587fb.tar.bz2 linux-stable-c7b9adaf85f818d747eeff5145eb4095ccd587fb.zip |
arm64: entry: Add exception trampoline page for exceptions from EL0
To allow unmapping of the kernel whilst running at EL0, we need to
point the exception vectors at an entry trampoline that can map/unmap
the kernel on entry/exit respectively.
This patch adds the trampoline page, although it is not yet plugged
into the vector table and is therefore unused.
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 | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d454d8ed45e4..716b5ef42e29 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -28,6 +28,8 @@ #include <asm/errno.h> #include <asm/esr.h> #include <asm/irq.h> +#include <asm/memory.h> +#include <asm/mmu.h> #include <asm/processor.h> #include <asm/ptrace.h> #include <asm/thread_info.h> @@ -943,6 +945,90 @@ __ni_sys_trace: .popsection // .entry.text +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 +/* + * Exception vectors trampoline. + */ + .pushsection ".entry.tramp.text", "ax" + + .macro tramp_map_kernel, tmp + mrs \tmp, ttbr1_el1 + sub \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + bic \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + .endm + + .macro tramp_unmap_kernel, tmp + mrs \tmp, ttbr1_el1 + add \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE) + orr \tmp, \tmp, #USER_ASID_FLAG + msr ttbr1_el1, \tmp + /* + * We avoid running the post_ttbr_update_workaround here because the + * user and kernel ASIDs don't have conflicting mappings, so any + * "blessing" as described in: + * + * http://lkml.kernel.org/r/56BB848A.6060603@caviumnetworks.com + * + * will not hurt correctness. Whilst this may partially defeat the + * point of using split ASIDs in the first place, it avoids + * the hit of invalidating the entire I-cache on every return to + * userspace. + */ + .endm + + .macro tramp_ventry, regsize = 64 + .align 7 +1: + .if \regsize == 64 + msr tpidrro_el0, x30 // Restored in kernel_ventry + .endif + tramp_map_kernel x30 + ldr x30, =vectors + prfm plil1strm, [x30, #(1b - tramp_vectors)] + msr vbar_el1, x30 + add x30, x30, #(1b - tramp_vectors) + isb + br x30 + .endm + + .macro tramp_exit, regsize = 64 + adr x30, tramp_vectors + msr vbar_el1, x30 + tramp_unmap_kernel x30 + .if \regsize == 64 + mrs x30, far_el1 + .endif + eret + .endm + + .align 11 +ENTRY(tramp_vectors) + .space 0x400 + + tramp_ventry + tramp_ventry + tramp_ventry + tramp_ventry + + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 + tramp_ventry 32 +END(tramp_vectors) + +ENTRY(tramp_exit_native) + tramp_exit +END(tramp_exit_native) + +ENTRY(tramp_exit_compat) + tramp_exit 32 +END(tramp_exit_compat) + + .ltorg + .popsection // .entry.tramp.text +#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ + /* * Special system call wrappers. */ |