> Every system call must go through ntdll.dll or it'll stop working on the next ... | Hacker News

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haberman on July 14, 2014 | parent | context | favorite | on: A ToC of the 20-part linker essay (2008)

> Every system call must go through ntdll.dll or it'll stop working on the next major upgrade, which will scramble the system call numbers.

Wow, really? So you can't make system calls from assembly language on Windows?

> It places fewer constraints on the kernel and lets you implement 32-bit-to-64-bit system call thunks entirely in userspace, completely avoiding a major class of security vulnerability.

Well, there is VDSO. What kind of thunks and security vulnerabilities are you talking about though?

quotemstr on July 14, 2014 [–]

> Wow, really? So you can't make system calls from assembly language on Windows?

Of course you can. Just go through the system DLL like any other program.

> What kind of thunks and security vulnerabilities are you talking about though?

Something like http://xorl.wordpress.com/2009/08/07/cve-2007-4573-linux-ker..., though that's not the only one.

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