From 4b65a5db362783ab4b04ca1c1d2ad70ed9b0ba2a Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 1 Jul 2016 16:53:00 +0100 Subject: arm64: Introduce uaccess_{disable,enable} functionality based on TTBR0_EL1 This patch adds the uaccess macros/functions to disable access to user space by setting TTBR0_EL1 to a reserved zeroed page. Since the value written to TTBR0_EL1 must be a physical address, for simplicity this patch introduces a reserved_ttbr0 page at a constant offset from swapper_pg_dir. The uaccess_disable code uses the ttbr1_el1 value adjusted by the reserved_ttbr0 offset. Enabling access to user is done by restoring TTBR0_EL1 with the value from the struct thread_info ttbr0 variable. Interrupts must be disabled during the uaccess_ttbr0_enable code to ensure the atomicity of the thread_info.ttbr0 read and TTBR0_EL1 write. This patch also moves the get_thread_info asm macro from entry.S to assembler.h for reuse in the uaccess_ttbr0_* macros. Cc: Will Deacon Cc: James Morse Cc: Kees Cook Cc: Mark Rutland Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/assembler.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'arch/arm64/include/asm/assembler.h') diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 55752231055c..446f6c46d4b1 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -41,6 +41,15 @@ msr daifclr, #2 .endm + .macro save_and_disable_irq, flags + mrs \flags, daif + msr daifset, #2 + .endm + + .macro restore_irq, flags + msr daif, \flags + .endm + /* * Enable and disable debug exceptions. */ @@ -406,6 +415,13 @@ alternative_endif movk \reg, :abs_g0_nc:\val .endm +/* + * Return the current thread_info. + */ + .macro get_thread_info, rd + mrs \rd, sp_el0 + .endm + /* * Errata workaround post TTBR0_EL1 update. */ -- cgit v1.2.3