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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2007-09-10 04:31:59 +0000 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2007-09-10 04:31:59 +0000 |
| commit | d739f5f8c71e6b173c75a806fb47110b4dcb61a9 (patch) | |
| tree | ed7fcb633e773aaae9e2c8ee8fb49fddeba83159 | |
| parent | d9a0b2a566a3d22c75332f6d9a6f60c5e445b533 (diff) | |
| download | man-pages-d739f5f8c71e6b173c75a806fb47110b4dcb61a9.tar.gz | |
Add text describing limit on total size of argv + evnp,
and changes that occurred with 2.6.23.
Add getopt(3) to SEE ALSO list.
| -rw-r--r-- | man2/execve.2 | 44 |
1 files changed, 43 insertions, 1 deletions
diff --git a/man2/execve.2 b/man2/execve.2 index 0f771abb00..3969b2b668 100644 --- a/man2/execve.2 +++ b/man2/execve.2 @@ -31,8 +31,10 @@ .\" Modified 2004-06-23 by Michael Kerrisk <mtk-manpages@gmx.net> .\" 2006-09-04 Michael Kerrisk <mtk-manpages@gmx.net> .\" Added list of process attributes that are not preserved on exec(). +.\" 2007-09-14 Ollie Wild <aaw@google.com>, mtk +.\" Add text describing limits on command-line arguments + environment .\" -.TH EXECVE 2 2006-09-04 "Linux" "Linux Programmer's Manual" +.TH EXECVE 2 2007-09-14 "Linux" "Linux Programmer's Manual" .SH NAME execve \- execute program .SH SYNOPSIS @@ -276,6 +278,45 @@ For portable use, .I optional-arg should either be absent, or be specified as a single word (i.e., it should not contain white space); see NOTES below. +.SS "Limits on size of arguments + environment" +Most Unix implementations impose some limit on the total size +of the command-line argument +.RI ( argv ) +and environment +.RI ( envp ) +strings that may be passed to a new program. +POSIX.1 allows an implementation to advertise this limit using the +.BR ARG_MAX +constant (either defined in +.I <limits.h> +or available at run time using the call +.IR "sysconf(_SC_ARG_MAX)" ). + +On Linux prior to kernel 2.6.23, the memory used to store the +environment and argument strings was limited to 32 pages +(defined by the kernel constant +.BR MAX_ARG_PAGES ). +On architectures with a 4-kB page size, +this yields a maximum size of 128 kB. + +On kernel 2.6.23 and later, most architectures support a size limit +derived from the soft +.B RLIMIT_STACK +resource limit (see +.BR getrlimit (2)). +For +these architectures, the total size is limited to 1/4 of the allowed +stack size, the limit per string is 32 pages (the kernel constant +.BR MAX_ARG_STRLEN), +and the maximum number of strings is 0x7FFFFFFF. +(This change allows programs to have a much larger +argument and/or environment list. +Imposing the 1/4-limit +ensures that the new program always has some stack space.) +Architectures with no memory management unit are excepted: +they maintain the pre-2.6.23 limit. +.\" Ollie: That doesn't include the lists of pointers, though, +.\" so the actual usage is a bit higher (1 pointer per argument). .SH "RETURN VALUE" On success, .BR execve () @@ -552,6 +593,7 @@ argv[4]: world .BR ptrace (2), .BR execl (3), .BR fexecve (3), +.BR getopt (3), .BR environ (7), .BR credentials (7), .BR path_resolution (7), |