Date: Fri, 10 Aug 2012 21:47:59 +0900 From: Murali Vijayaraghavan <vmurali@...il.mit.edu> To: musl@...ts.openwall.com Subject: Using unistd functions vs calling syscall straight in the code Hi I am trying to run C programs on a barebones (MIPS-like) processor simulator without any OS. The simulator mainly implements the userspace ISA, with no syscall instruction support in hardware. I was hoping to instead support some of the system calls (like open, read, write, etc, mainly for debugging purposes) by using custom instructions, one for each (or a few similar) system call(s). For that, the implementation of functions like read and write should be calling these custom instructions in assembly, in other words, I have to port the system call layer to my simulator. I looked at musl among other libc implementations, and this was the only one whose structure I could understand well, making it easy to port. I did successfully and easily port it for my purposes, which brings to my question/comment. You guys do have a unistd implementation which supposedly implements each of the system calls. But you are not consistent with the use of these functions to perform the unistd-implemented tasks. Wouldn't it be a lot cleaner to call these functions instead of calling syscall / syscall_cp directly from the other (top-level) functions? Was there some rationale or is it just code evolution? Thanks Murali Content of type "text/html" skipped
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