Fix build with musl and older Linux kernel #82
Conversation
The musl libc carries its own copy of Linux system calls. When building
with Linux headers older than v3.17, musl provides SYS_getrandom
definition, but not GRND_NONBLOCK. This causes build failure for
libressl and openntpd:
getentropy_linux.c: In function 'getentropy_getrandom':
getentropy_linux.c:205:42: error: 'GRND_NONBLOCK' undeclared (first use in this function)
ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
^~~~~~~~~~~~~
Define GRND_NONBLOCK locally when its definition is missing to fix the
build. There should be no run-time effect. Older kernels return ENOSYS
for unsupported syscall().
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@4a6f656c Who will handle this PR? |
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Just so I understand, what prevents you from just using newer headers? Musl AFAIK does not actually use Kernel headers itself for enabling features at all, unlike Glibc. |
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@busterb When the target system uses older kernel I prefer to use kernel headers of the same version to minimize the risk of breakage. But regardless, the entire function is under the |
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OK, I can see that. It's odd if Musl is defining syscall definitions itself that are accessible from userspace software, shadowing the kernel syscall definitions. |
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This seems like an issue with the musl headers - defining If we want to support this (somewhat broken) use case, then it probably should be with: #if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
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That works for me @4a6f656c since we do need both. If you don't have the right kernel for this, you'll get an ENOSYS anyway, so the path will fall through in a suboptimal way. Previously, we wouldn't compile the fall back code path if the syscall was defined. |
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Should I post an updated pull request along the lines of @4a6f656c suggestion? |
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No need, this will go into upstream CVS. This repo is just a mirror, so git pull requests don't apply anyway. |
…getrandom(2) Based on discussion here #82 Suggested fix from jsing@
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Updated upstream, thanks all! |
…getrandom(2) Based on discussion here libressl/openbsd#82 Suggested fix from jsing@
The musl libc carries its own copy of Linux system calls. When building
with Linux headers older than v3.17, musl provides SYS_getrandom
definition, but not GRND_NONBLOCK. This causes build failure for
libressl and openntpd:
getentropy_linux.c: In function 'getentropy_getrandom':
getentropy_linux.c:205:42: error: 'GRND_NONBLOCK' undeclared (first use in this function)
ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
^~~~~~~~~~~~~
Define GRND_NONBLOCK locally when its definition is missing to fix the
build. There should be no run-time effect. Older kernels return ENOSYS
for unsupported syscall().