SGDT/SIDT Fiction and Reality (2017)

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10 pointsuserbinator2 comments

Probably a dumb question, but can someone explain why these instructions exist?

In user mode, their values are completely irrelevant. Only the kernel can use the value, but the kernel could just store whatever it gave to lgdt/lidt.

The article mentions win32s running them, so they must serve some purpose. I just wonder which.

Only the kernel can use the value, but the kernel could just store whatever it gave to lgdt/lidt.

User and kernel mode were far less isolated in those OSs. Also, write-only registers are usually discouraged.

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