From 39bc88e5e38e9b213bd7d833ce0df6ec029761ad Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 2 Sep 2016 14:54:03 +0100 Subject: 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 Cc: James Morse Cc: Kees Cook Cc: Mark Rutland Signed-off-by: Catalin Marinas --- arch/arm64/kernel/traps.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'arch/arm64/kernel/traps.c') diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 4731133286b3..5b830be79c01 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -440,9 +440,10 @@ int cpu_enable_cache_maint_trap(void *__unused) } #define __user_cache_maint(insn, address, res) \ - if (untagged_addr(address) >= user_addr_max()) \ + if (untagged_addr(address) >= user_addr_max()) { \ res = -EFAULT; \ - else \ + } else { \ + uaccess_ttbr0_enable(); \ asm volatile ( \ "1: " insn ", %1\n" \ " mov %w0, #0\n" \ @@ -454,7 +455,9 @@ int cpu_enable_cache_maint_trap(void *__unused) " .popsection\n" \ _ASM_EXTABLE(1b, 3b) \ : "=r" (res) \ - : "r" (address), "i" (-EFAULT) ) + : "r" (address), "i" (-EFAULT)); \ + uaccess_ttbr0_disable(); \ + } static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs) { -- cgit v1.2.3