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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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arch/arm64/include/uapi/asm/ptrace.h
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@@ -45,6 +45,7 @@
#define PSR_A_BIT 0x00000100
#define PSR_D_BIT 0x00000200
#define PSR_PAN_BIT 0x00400000
#define PSR_UAO_BIT 0x00800000
#define PSR_Q_BIT 0x08000000
#define PSR_V_BIT 0x10000000
#define PSR_C_BIT 0x20000000