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Diffstat (limited to 'glibc/mmap.mdwn')
| -rw-r--r-- | glibc/mmap.mdwn | 98 |
1 files changed, 0 insertions, 98 deletions
diff --git a/glibc/mmap.mdwn b/glibc/mmap.mdwn deleted file mode 100644 index 09b0b65d..00000000 --- a/glibc/mmap.mdwn +++ /dev/null @@ -1,98 +0,0 @@ -[[!meta copyright="Copyright © 2012 Free Software Foundation, Inc."]] - -[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable -id="license" text="Permission is granted to copy, distribute and/or modify this -document under the terms of the GNU Free Documentation License, Version 1.2 or -any later version published by the Free Software Foundation; with no Invariant -Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled [[GNU Free Documentation -License|/fdl]]."]]"""]] - -There are two implementations of `mmap` for GNU Hurd: -`sysdeps/mach/hurd/mmap.c` (main implementation) and -`sysdeps/mach/hurd/dl-sysdep.c` (*Minimal mmap implementation sufficient for -initial loading of shared libraries.*). - - * `MAP_COPY` - - What exactly is that? `elf/dl-load.c` has some explanation. - <http://lkml.indiana.edu/hypermail/linux/kernel/0110.1/1506.html> - - It is only handled in `dl-sysdep.c`, when `flags & (MAP_COPY|MAP_PRIVATE)` - is used for `vm_map`'s `copy` parameter, and `mmap.c` uses `! (flags & - MAP_SHARED)` instead, which seems inconsistent? - - -# `io_map` Failure - -This is the [[libnetfs: `io_map`|open_issues/libnetfs_io_map]] issue. - -[[!tag open_issue_glibc]] - -Review of `mmap` usage in generic bits of glibc, based on -a1bcbd4035ac2483dc10da150d4db46f3e1744f8 (2012-03-11), listing these cases -where failure (due to `io_map` failing; that is, invocations where a `fd` is -passed) is not properly handled. - -`catgets/open_catalog.c`, `iconv/gconv_cache.c`, `intl/loadmsgcat.c`, -`locale/loadlocale.c` have fallback code for the `MAP_FAILED` case. - -[[tschwinge]]'s current plan is to make the following cases do the same (if -that is possible); probably by introducing a generic `mmap_or_read` function, -that first tries `mmap` (and that will succeed on Linux-based systems and also -on Hurd-based, if it's backed by [[hurd/libdiskfs]]), and if that fails tries -`mmap` on anonymous memory and then fills it by `read`ing the required data. -This is also what the [[hurd/exec]] server is doing (and is the reason that the -`./true` invocation on [[libnetfs: `io_map`|open_issues/libnetfs_io_map]] -works, to my understanding): see `exec.c:prepare`, if `io_map` fails, -`e->filemap == MACH_PORT_NULL`; then `exec.c:map` (as invoked from -`exec.c:load_section`, `exec.c:check_elf`, `exec.c:do_exec`, or -`hashexec.c:check_hashbang`) will use `io_read` instead. - -Doing so potentially means reading in a lot of unused data -- but we probably -can't do any better? - -In parallel (or even alternatively?), it should be researched how Linux (or any -other kernel) implements `mmap` on NFS and similar file systems, and then -implement the same in [[hurd/libnetfs]] and/or [[hurd/translator/nfs]], etc. - -Here, also probably the whole mapping region [has to be -read](http://lists.gnu.org/archive/html/bug-hurd/2001-10/msg00306.html) at -`mmap` time. - -List of files without fallback code for the *`MAP_FAILED` due to `io_map` -failed* case: - - * `elf/cache.c` - - * `elf/dl-load.c` - - * `elf/dl-misc.c` - - * `elf/dl-profile.c` - - * `elf/readlib.c` - - * `elf/sprof.c` - - * `locale/loadarchive.c` - - * `locale/programs/locale.c` - - * `locale/programs/locarchive.c` - - * `nscd/connections.c` - - * `nscd/nscd_helper.c` - - * `nss/makedb.c` - - * `nss/nss_db/db-open.c` - - * Omitted: - - * `nptl/` - - * `sysdeps/unix/sparc/` - - * `sysdepts/unix/sysv/linux/` |