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| author |   Catalin Marinas <catalin.marinas@arm.com> | 2016-09-02 14:54:03 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-11-21 18:48:54 +0000 |
| commit | 39bc88e5e38e9b213bd7d833ce0df6ec029761ad (patch) | |
| tree | 767472a4cbe749b81e76d692402dc756b4e2f54d /arch/arm64/mm | |
| parent | arm64: Introduce uaccess_{disable,enable} functionality based on TTBR0_EL1 (diff) | |
| download | linux-dev-39bc88e5e38e9b213bd7d833ce0df6ec029761ad.tar.xz linux-dev-39bc88e5e38e9b213bd7d833ce0df6ec029761ad.zip | |
arm64: Disable TTBR0_EL1 during normal kernel execution
When the TTBR0 PAN feature is enabled, the kernel entry points need to
disable access to TTBR0_EL1. The PAN status of the interrupted context
is stored as part of the saved pstate, reusing the PSR_PAN_BIT (22).
Restoring access to TTBR0_EL1 is done on exception return if returning
to user or returning to a context where PAN was disabled.
Context switching via switch_mm() must defer the update of TTBR0_EL1
until a return to user or an explicit uaccess_enable() call.
Special care needs to be taken for two cases where TTBR0_EL1 is set
outside the normal kernel context switch operation: EFI run-time
services (via efi_set_pgd) and CPU suspend (via cpu_(un)install_idmap).
Code has been added to avoid deferred TTBR0_EL1 switching as in
switch_mm() and restore the reserved TTBR0_EL1 when uninstalling the
special TTBR0_EL1.
User cache maintenance (user_cache_maint_handler and
__flush_cache_user_range) needs the TTBR0_EL1 re-instated since the
operations are performed by user virtual address.
This patch also removes a stale comment on the switch_mm() function.
Cc: Will Deacon <will.deacon@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/mm')
| -rw-r--r-- | arch/arm64/mm/cache.S | 6 | ||||
| -rw-r--r-- | arch/arm64/mm/context.c | 7 |
2 files changed, 11 insertions, 2 deletions
diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 58b5a906ff78..da9576932322 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -23,6 +23,7 @@ #include <asm/assembler.h> #include <asm/cpufeature.h> #include <asm/alternative.h> +#include <asm/uaccess.h> /* * flush_icache_range(start,end) @@ -48,6 +49,7 @@ ENTRY(flush_icache_range) * - end - virtual end address of region */ ENTRY(__flush_cache_user_range) + uaccess_ttbr0_enable x2, x3 dcache_line_size x2, x3 sub x3, x2, #1 bic x4, x0, x3 @@ -69,10 +71,12 @@ USER(9f, ic ivau, x4 ) // invalidate I line PoU dsb ish isb mov x0, #0 +1: + uaccess_ttbr0_disable x1 ret 9: mov x0, #-EFAULT - ret + b 1b ENDPROC(flush_icache_range) ENDPROC(__flush_cache_user_range) diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index efcf1f7ef1e4..4c63cb154859 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -221,7 +221,12 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) raw_spin_unlock_irqrestore(&cpu_asid_lock, flags); switch_mm_fastpath: - cpu_switch_mm(mm->pgd, mm); + /* + * Defer TTBR0_EL1 setting for user threads to uaccess_enable() when + * emulating PAN. + */ + if (!system_uses_ttbr0_pan()) + cpu_switch_mm(mm->pgd, mm); } static int asids_init(void) |