SYSENTER: Difference between revisions
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SYSCALL saves "return RIP" into ECX, so caller doesn't need to do this..
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*CSTAR (0xC0000083) - The kernel's RIP for SYSCALL in compatibility mode.
*SFMASK (0xC0000084) - The low 32 bits are the SYSCALL flag mask. If a bit in this is set, the corresponding bit in rFLAGS is cleared.
===Operation===
NOTE: these instructions assume a flat segmented memory model (paging allowed). They require that "the code-segment base, limit, and attributes (except for CPL) are consistent for all application and system processes." --AMD System programming
SYSCALL loads CS from STAR 47:32. It masks EFLAGS with SFMASK. Next it stores EIP in ECX. It then loads EIP from STAR 32:0 and SS from STAR 47:32 + 8. It then executes.
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