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2190fed67b
Provide hooks into the kernel entry and exit paths to permit control of userspace visibility to the kernel. The intended use is: - on entry to kernel from user, uaccess_disable will be called to disable userspace visibility - on exit from kernel to user, uaccess_enable will be called to enable userspace visibility - on entry from a kernel exception, uaccess_save_and_disable will be called to save the current userspace visibility setting, and disable access - on exit from a kernel exception, uaccess_restore will be called to restore the userspace visibility as it was before the exception occurred. These hooks allows us to keep userspace visibility disabled for the vast majority of the kernel, except for localised regions where we want to explicitly access userspace. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
39 lines
1.1 KiB
ArmAsm
39 lines
1.1 KiB
ArmAsm
/*
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* The ARM LDRD and Thumb LDRSB instructions use bit 20/11 (ARM/Thumb)
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* differently than every other instruction, so it is set to 0 (write)
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* even though the instructions are read instructions. This means that
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* during an abort the instructions will be treated as a write and the
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* handler will raise a signal from unwriteable locations if they
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* fault. We have to specifically check for these instructions
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* from the abort handlers to treat them properly.
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*
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*/
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.macro do_thumb_abort, fsr, pc, psr, tmp
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tst \psr, #PSR_T_BIT
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beq not_thumb
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ldrh \tmp, [\pc] @ Read aborted Thumb instruction
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uaccess_disable ip @ disable userspace access
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and \tmp, \tmp, # 0xfe00 @ Mask opcode field
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cmp \tmp, # 0x5600 @ Is it ldrsb?
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orreq \tmp, \tmp, #1 << 11 @ Set L-bit if yes
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tst \tmp, #1 << 11 @ L = 0 -> write
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orreq \fsr, \fsr, #1 << 11 @ yes.
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b do_DataAbort
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not_thumb:
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.endm
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/*
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* We check for the following instruction encoding for LDRD.
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*
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* [27:25] == 000
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* [7:4] == 1101
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* [20] == 0
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*/
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.macro teq_ldrd, tmp, insn
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mov \tmp, #0x0e100000
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orr \tmp, #0x000000f0
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and \tmp, \insn, \tmp
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teq \tmp, #0x000000d0
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.endm
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