66 lines
1.3 KiB
ArmAsm
66 lines
1.3 KiB
ArmAsm
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.globl _check_context_loop
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.globl _remaining_invocations
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.globl _origstate
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.globl _newstate
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#define JUNK 0xCC0FFEE0
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#define COPY(dest, offset) \
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mov $dest, %ebp ; \
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mov 4*offset(%esp), %ebx ; \
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mov %ebx, 4*offset(%ebp) ;
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/* Copy the result of a pusha to dest. */
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#define COPYA(dest) \
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COPY(dest, 0); COPY(dest, 1); COPY(dest, 2); COPY(dest, 3); \
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COPY(dest, 4); COPY(dest, 5); COPY(dest, 6); COPY(dest, 7);
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.text
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/* void check_context_loop() */
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_check_context_loop:
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/* Save original context so we can restore it. */
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pusha
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/* Put some junk in the registers.
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* We want to junk the state, and junk it differently per reg,
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* so it's likelier corruption is actually detected. We can't
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* touch %esp but we can verify that it doesn't change from its
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* current value.
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*/
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mov $JUNK+1, %eax
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mov $JUNK+2, %ebx
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mov $JUNK+3, %ecx
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mov $JUNK+4, %edx
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mov $JUNK+5, %ebp
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mov $JUNK+6, %esi
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mov $JUNK+7, %edi
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/* Save the junked state so we can compare it. */
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pusha
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cont:
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/* Check if we're done. */
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cmpl $0, (_remaining_invocations)
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jz done
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/* We're not done. */
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/* Restart loop. */
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jmp cont
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done:
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/* Save the junked, but should be unmodified state
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* so we can copy it.
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*/
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pusha
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COPYA(_newstate);
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popa
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/* copy and restore junked state */
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COPYA(_origstate);
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popa
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/* restore original state and return */
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popa
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ret
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