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Message-Id: <20230302051656.260369-1-izbyshev@ispras.ru>
Date: Thu, 2 Mar 2023 08:16:56 +0300
From: Alexey Izbyshev <izbyshev@...ras.ru>
To: musl@...ts.openwall.com
Subject: [PATCH] poll: fix timespec kernel ABI mismatch on 32-bit arches without SYS_poll
After migration to 64-bit time_t in struct timespec, passing it to
SYS_ppoll on arches where the syscall expects the 32-bit version of
the struct became wrong and results in overlaying 64-bit tv_sec over the
whole expected struct. In this case, tv_nsec is completely ignored, and
interpretation of tv_sec depends on endianness. Because its value in the
case of poll fits into 32 bits, on little endian arches tv_sec is
interpreted as the correct number of seconds and zero nanoseconds, so
the original timeout is effectively rounded down to seconds. On big
endian arches, tv_sec is interpreted as nanoseconds (and zero seconds),
so the original timeout is effectively divided by 10^9 and rounded down
to nanoseconds.
The only in-tree affected arch is or1k, which is big endian.
Fix this by passing the timeout in the array of the type actually
expected by the kernel for SYS_ppoll, as done in other time64-related
code.
---
src/select/poll.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/select/poll.c b/src/select/poll.c
index c84c8a99..d1caefcc 100644
--- a/src/select/poll.c
+++ b/src/select/poll.c
@@ -8,8 +8,14 @@ int poll(struct pollfd *fds, nfds_t n, int timeout)
#ifdef SYS_poll
return syscall_cp(SYS_poll, fds, n, timeout);
#else
- return syscall_cp(SYS_ppoll, fds, n, timeout>=0 ?
- &((struct timespec){ .tv_sec = timeout/1000,
- .tv_nsec = timeout%1000*1000000 }) : 0, 0, _NSIG/8);
+ time_t s = timeout>=0 ? timeout/1000 : 0;
+ long ns = timeout>=0 ? timeout%1000*1000000 : 0;
+#ifdef SYS_ppoll_time64
+ if (SYS_ppoll == SYS_ppoll_time64)
+ return syscall_cp(SYS_ppoll_time64, fds, n,
+ timeout>=0 ? ((long long[]){s, ns}) : 0, 0, _NSIG/8);
+#endif
+ return syscall_cp(SYS_ppoll, fds, n,
+ timeout>=0 ? ((long[]){s, ns}) : 0, 0, _NSIG/8);
#endif
}
--
2.39.1
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