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