SYSENTER: Difference between revisions

SYSENTER (view source)

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Revision as of 17:54, 10 May 2022 (view source) osdev>Demindiro m (Explicitly note that SS is still loaded from STAR 63:48 + 8. Thanks AMD) ← Older edit		Latest revision as of 14:54, 10 July 2023 (view source) osdev>Khaledhammouda No edit summary
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Line 64: ====64 bit mode==== The operation in 64 bit mode is the same, except that RIP is loaded from LSTAR, or CSTAR of in IA32-e submode (A.K.A. compatibility mode). It also respectively saves and loads RFLAGS to and from R11. ~~As well, in~~'''In Long Mode, userland CS will be loaded from STAR 63:48 + 16 and userland SS from STAR 63:48 + 8 on SYSRET. ~~Therefore, you~~You ~~might~~may need to ~~setup~~modify your GDT accordingly.''' Moreover, SYSRET will return to compatibility mode if the operand size is set to 32 bits, which is, for instance, nasm's default. To explicitly request a return into long mode, set the operand size to 64 bits (e.g. "o64 sysret" with nasm). Line 83 ⟶ 84: *https://cdrdv2.intel.com/v1/dl/getContent/671200 Page 1882 for SYSRET [[Category:System Calls]]