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arm64: kernel: Add support for User Access Override

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'User Access Override' is a new ARMv8.2 feature which allows the
unprivileged load and store instructions to be overridden to behave in
the normal way.

This patch converts {get,put}_user() and friends to use ldtr*/sttr*
instructions - so that they can only access EL0 memory, then enables
UAO when fs==KERNEL_DS so that these functions can access kernel memory.

This allows user space's read/write permissions to be checked against the
page tables, instead of testing addr<USER_DS, then using the kernel's
read/write permissions.

Signed-off-by: James Morse <james.morse@arm.com>
[catalin.marinas@arm.com: move uao_thread_switch() above dsb()]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
James Morse
2016-02-05 14:58:48 +00:00
committed by Catalin Marinas
parent 406e308770
commit 57f4959bad
15 changed files with 213 additions and 39 deletions
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3
arch/arm64/include/asm/sysreg.h
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@@ -79,9 +79,12 @@
#define SYS_DCZID_EL0 sys_reg(3, 3, 0, 0, 7)
#define REG_PSTATE_PAN_IMM sys_reg(0, 0, 4, 0, 4)
#define REG_PSTATE_UAO_IMM sys_reg(0, 0, 4, 0, 3)
#define SET_PSTATE_PAN(x) __inst_arm(0xd5000000 | REG_PSTATE_PAN_IMM |\
(!!x)<<8 | 0x1f)
#define SET_PSTATE_UAO(x) __inst_arm(0xd5000000 | REG_PSTATE_UAO_IMM |\
(!!x)<<8 | 0x1f)
/* SCTLR_EL1 */
#define SCTLR_EL1_CP15BEN (0x1 << 5)