diff options
Diffstat (limited to 'glibc/mmap.mdwn')
| -rw-r--r-- | glibc/mmap.mdwn | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/glibc/mmap.mdwn b/glibc/mmap.mdwn index d0c492e9..09b0b65d 100644 --- a/glibc/mmap.mdwn +++ b/glibc/mmap.mdwn @@ -20,12 +20,12 @@ initial loading of shared libraries.*). 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. + MAP_SHARED)` instead, which seems inconsistent? # `io_map` Failure -[[libnetfs: `io_map`|open_issues/libnetfs_io_map]] issue. +This is the [[libnetfs: `io_map`|open_issues/libnetfs_io_map]] issue. [[!tag open_issue_glibc]] @@ -41,11 +41,27 @@ passed) is not properly handled. 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 -- -but this would probably means all :-/ `PT_LOAD` segments for the ELF case? In -parallel, 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]]/[[hurd/translator/nfs]]. +`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` |