Date: Thu, 15 Aug 2019 12:08:13 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: libc-test regression/syscall-sign-extend.c libc-test has one test regression/syscall-sign-extend.c whose purpose is testing an x32 bug whereby pointers passed to syscall() got sign-extended, fixed by 5f95f965e933c5b155db75520ac27c92ddbcf400 (albeit with a nasty hack). However it's using SYS_clock_gettime as the test, which means it will break on 32-bit archs when time_t changes to 64-bit and the old syscall no longer matches the libc ABI types. (It also doesn't seem to be doing anything to ensure that the pointer is "negative" in a sign-extension case; it just assumes the stack is at the top of memory. But this probably doesn't matter in practice.) I think we should find a different syscall to test that's immune to kernel/libc disagreements over types or macro values. The simplest example might be SYS_read - opening a pipe, writing a byte to it with write(), and confirming that syscall(SYS_read, ...) reads it back. Alternatively clock_gettime could be tested just to modify the pointed-to memory (e.g. by pre-filling it with 0xff) without assuming it matches struct timespec layout, but that also assumes the CLOCK_* macros map directly to syscall API. Rich
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