[PATCH v3] getrlimit.2: old_getrlimit/ugetrlimit and RLIM_INFINITY discrepancies
STALE1894d
From: Eugene Syromyatnikov <hidden>
Date: 2021-07-29 15:44:11
Subsystem:
the rest · Maintainer:
Linus Torvalds
Historically, Linux didn't follow SUS with respect to RLIM_INFINITY signedness; it was changed during 2.4 development cycle, but in somewhat peculiar and arch-dependent fashion due to backward compatibility concerns. Signed-off-by: Eugene Syromyatnikov <redacted> --- man2/getrlimit.2 | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/man2/getrlimit.2 b/man2/getrlimit.2
index 648fd3c..5a360d4 100644
--- a/man2/getrlimit.2
+++ b/man2/getrlimit.2@@ -646,6 +646,37 @@ The name of the glibc wrapper function is .BR prlimit (); the underlying system call is .BR prlimit64 (). +The corresponding infinity value constant is provided in +.I <linux/resource.h> +as +.BR RLIM64_INFINITY. +.PP +Original Linux implementation used signed types for limits; that was changed +(along with the value of the +.B RLIM_INFINITY +constant) +.\" http://repo.or.cz/davej-history.git/blobdiff/129f8758d8c41e0378ace0b6e2f56bbb8a1ec694..15305d2e69c3a838bacd78962c07077d2821f255:/include/linux/resource.h +during 2.4 development cycle, as it wasn't compatible +with Single UNIX Specification. +However, in order to preserve backward compatibility, the routine +.IR sys_old_getrlimit +has been implemented under +.B __NR_getrlimit +syscall slot, with infinity checks being performed against hard-coded 0x7fffffff +value, and the routine +.I sys_getrlimit +has been exposed under a new name, +.BR ugetrlimit (). +Note that most newer architectures don't have the latter, with +.BR getrlimit () +providing proper implementation. +Also worth noting that several architectures decided not to change +.B RLIM_INFINITY +value: 32-bit mips and sparc (but not 64-bit variants, that switched +to the new value of (~0UL)) retained the old 0x7fffffff value, +and alpha retained 0x7ffffffffffffffful. +.\" ...along with a request to call when one runs into it: +.\" https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/alpha/include/uapi/asm/resource.h#n15 .SH BUGS In older Linux kernels, the .B SIGXCPU
--
2.1.4