From 399644e47874bff147afb19c89228901ac39340e Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 15 Apr 2024 21:40:15 +0200 Subject: Adding upstream version 6.05.01. Signed-off-by: Daniel Baumann --- man3/getentropy.3 | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 man3/getentropy.3 (limited to 'man3/getentropy.3') diff --git a/man3/getentropy.3 b/man3/getentropy.3 new file mode 100644 index 0000000..f09a209 --- /dev/null +++ b/man3/getentropy.3 @@ -0,0 +1,103 @@ +.\" Copyright (C) 2017, Michael Kerrisk +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH getentropy 3 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +getentropy \- fill a buffer with random bytes +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include +.PP +.BI "int getentropy(void " buffer [. length "], size_t " length ); +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.BR getentropy (): +.nf + _DEFAULT_SOURCE +.fi +.SH DESCRIPTION +The +.BR getentropy () +function writes +.I length +bytes of high-quality random data to the buffer starting +at the location pointed to by +.IR buffer . +The maximum permitted value for the +.I length +argument is 256. +.PP +A successful call to +.BR getentropy () +always provides the requested number of bytes of entropy. +.SH RETURN VALUE +On success, this function returns zero. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EFAULT +Part or all of the buffer specified by +.I buffer +and +.I length +is not in valid addressable memory. +.TP +.B EIO +.I length +is greater than 256. +.TP +.B EIO +An unspecified error occurred while trying to overwrite +.I buffer +with random data. +.TP +.B ENOSYS +This kernel version does not implement the +.BR getrandom (2) +system call required to implement this function. +.SH STANDARDS +None. +.SH HISTORY +glibc 2.25. +OpenBSD. +.SH NOTES +The +.BR getentropy () +function is implemented using +.BR getrandom (2). +.PP +Whereas the glibc wrapper makes +.BR getrandom (2) +a cancelation point, +.BR getentropy () +is not a cancelation point. +.PP +.BR getentropy () +is also declared in +.BR . +(No feature test macro need be defined to obtain the declaration from +that header file.) +.PP +A call to +.BR getentropy () +may block if the system has just booted and the kernel has +not yet collected enough randomness to initialize the entropy pool. +In this case, +.BR getentropy () +will keep blocking even if a signal is handled, +and will return only once the entropy pool has been initialized. +.SH SEE ALSO +.BR getrandom (2), +.BR urandom (4), +.BR random (7) -- cgit v1.2.3