FROMLIST: arm64: Introduce uaccess_{disable,enable} functionality based on TTBR0_EL1
authorCatalin Marinas <catalin.marinas@arm.com>
Fri, 1 Jul 2016 15:53:00 +0000 (16:53 +0100)
committerSami Tolvanen <samitolvanen@google.com>
Thu, 29 Sep 2016 17:52:56 +0000 (10:52 -0700)
commit1911d36b27ba58ee18592df25b7ee636d4d4c41d
tree6e06a501afe513dff8ead40bb1b66cf9a69aa7a9
parent3b66929169de053042d47e482dd5748794756153
FROMLIST: 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 <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>
Change-Id: Idf09a870b8612dce23215bce90d88781f0c0c3aa
(cherry picked from commit 940d37234182d2675ab8ab46084840212d735018)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
arch/arm64/include/asm/assembler.h
arch/arm64/include/asm/cpufeature.h
arch/arm64/include/asm/kernel-pgtable.h
arch/arm64/include/asm/thread_info.h
arch/arm64/include/asm/uaccess.h
arch/arm64/kernel/asm-offsets.c
arch/arm64/kernel/cpufeature.c
arch/arm64/kernel/entry.S
arch/arm64/kernel/head.S
arch/arm64/kernel/vmlinux.lds.S