Hello Ollie,
Ollie Wild wrote:
> Michael,
>
> Per our previous discussion, here are the updates to the execve(2)
> manpage resulting from the variable length argument support patch in
> linux-2.6.23-rc1. The execve API is unmodified. However, the
> following should be noted in the "Notes" section.
>
> Prior to linux-2.6.23, the memory used to store the environment and
> argument list strings was limited to 32 (MAX_ARG_PAGES) pages. On
> most architectures, the page size is 4kB, leading to a maximum size of
> 128kB.
>
> In linux-2.6.23 and later, most architectures support a size limit
> derived from the current RLIMIT_STACK setting (see getrlimit(2)). For
> these architectures, the total size is limited to 1/4 the allowed
> stack size, the limit per string is 32 pages (MAX_ARG_STRLEN), and the
> maximum number of strings is 0x7FFFFFFF. Architectures with no memory
> management unit are excepted: they maintain the pre-2.6.23 limit.
Thanks. For man-pages-2.66 I have added the following text to execve.2:
Limits on size of arguments + environment
Most Unix implementations impose some limit on the total size
of the command-line argument (argv) and environment (envp)
strings that may be passed to a new program. POSIX.1 allows
an implementation to advertise this limit using the ARG_MAX
constant (either defined in <limits.h> or available at run
time using the call 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 MAX_ARG_PAGES). On architec-
tures 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 RLIMIT_STACK resource limit (see
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 MAX_ARG_STRLEN), and
the maximum number of strings is 0x7FFFFFFF. (This change
allows programs to have a much larger argument and/or envi-
ronment 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.
Cheers,
Michael
--
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7
Want to help with man page maintenance? Grab the latest tarball at
http://www.kernel.org/pub/linux/docs/manpages/
read the HOWTOHELP file and grep the source files for 'FIXME'.
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