src/libexec/rtld-elf/map_object.c, branch releng/8.1

Merge r197808 from head to stable/8:

2009-12-14T12:19:21Z

In rtld's map_object(), use pread(..., 0) rather than read() to read the ELF header from the front of the file. As all other I/O on the binary is done using mmap(), this avoids the need for seek privileges on the file descriptor during run-time linking. Sponsored by: Google

Only perform .bss mapping and cleaning operations when segment file size

2009-07-17T19:32:04Z

is not equal to its memory size. This eliminates unneeded clearing of the text segment that often happens due to text end not being page-aligned. For instance, $ readelf -l /lib/libedit.so.6 Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x00000000 0x00000000 0x139e1 0x139e1 R E 0x1000 LOAD 0x014000 0x00014000 0x00014000 0x00f04 0x00f14 RW 0x1000 DYNAMIC 0x014cc4 0x00014cc4 0x00014cc4 0x000d0 0x000d0 RW 0x4 $ procstat -v $$ (for /bin/sh) 68585 0x28097000 0x280aa000 r-x 6 0 21 14 CN vn /lib/libedit.so.6 68585 0x280aa000 0x280ab000 r-x 1 0 1 0 CN vn /lib/libedit.so.6 <== 68585 0x280ab000 0x280ac000 rwx 1 0 1 0 CN vn /lib/libedit.so.6 Note the splitted map entry marked by '<=='. Reviewed by: kan Approved by: re (kensmith) MFC after: 1 month

Currently, when mapping an object, rtld reserves the whole address space

2009-04-10T10:14:04Z

for the mapping by the object' file with the protection and mode of the first loadable segment over the whole region. Then, it maps other segments at the appropriate addresses inside the region. On amd64, due to default alignment of the segments being 1Gb, the subsequent segment mappings leave the holes in the region, that usually contain mapping of the object' file past eof. Such mappings prevent wiring of the address space, because the pages cannot be faulted in. Change the way the mapping of the ELF objects is constructed, by first mapping PROT_NONE anonymous memory over the whole range, and then mapping the segments of the object over it. Take advantage of this new order and allocate .bss by changing the protection of the range instead of remapping. Note that we cannot simply keep the holes between segments, because other mappings may be made there. Among other issues, when the dso is unloaded, rtld unmaps the whole region, deleting unrelated mappings. The kernel ELF image activator does put the holes between segments, but this is not critical for now because kernel loads only executable image and interpreter, both cannot be unloaded. This will be fixed later, if needed. Reported and tested by: Hans Ottevanger Suggested and reviewed by: kan, alc

Update comment to the reality, rtld supports any number of loadable segments.

2009-04-10T09:52:42Z

Fix spacing. Reviewed by: kan

Implement the dynamic string token substitution in the rpath and

2009-03-18T13:40:37Z

soneeded pathes. The $ORIGIN, $OSNAME, $OSREL and $PLATFORM tokens are supported. Enabling the substitution requires DF_ORIGIN flag in DT_FLAGS or DF_1_ORIGIN if DF_FLAGS_1, that may be set with -z origin gnu ld flag. Translation is unconditionally disabled for setuid/setgid processes. The $ORIGIN translation relies on the AT_EXECPATH auxinfo supplied by kernel. Requested by: maho Tested by: maho, pho Reviewed by: kan

Implement dl_iterate_phdr function.

2007-04-03T18:31:20Z

Convert boolean flags in internal Obj_Entry structure into bitfields. Properly check for loaded segment alignment in map_object.

Implement ELF symbol versioning using GNU semantics. This code aims

2005-12-18T19:43:33Z

to be compatible with symbol versioning support as implemented by GNU libc and documented by http://people.redhat.com/~drepper/symbol-versioning and LSB 3.0. Implement dlvsym() function to allow lookups for a specific version of a given symbol.

Attempt to free any static TLS space used by a shared library when it

2005-02-27T12:55:40Z

is unloaded. This allows applications which load and unload libraries like libGL.so.1 several times to work properly. MFC after: 2 days

Add support for Thread Local Storage.

2004-08-03T08:51:00Z

- Add support for DT_FLAGS.

2003-06-18T03:34:29Z

- Define various things from the most recent ELF spec.