| 7f5c8f97 | 17-Mar-2012 |
John Marino <draco@marino.st> |
rtld: Add main object initialization and finalization
Since DragonFly's inception, crt1 has called _init and _fini functions of
the binary rather than leaving this task to the runtime linker. Likel
rtld: Add main object initialization and finalization
Since DragonFly's inception, crt1 has called _init and _fini functions of
the binary rather than leaving this task to the runtime linker. Likely
this was done in order to use the same crt code for both statically and
dynamically linked binaries.
When FreeBSD imported DragonFly's preinit, init, and fini array handling
code, they moved the _init and _fini calls to rtld. In order for rtld to
maintain compatiblity with binaries created with crt code that call these
functions, rtld looks for an ELF note that indicates the binary was built
with a crt that does not call _init and _fini.
This commit imports this capability as well as synchronizes some of the
changes FreeBSD made to the DragonFly code. Many of the differences
weren't necessary, but some represented improvements. In any case, it
benefits both operating systems to minimize the differences between the
runtime linkers in order to continue to collaborate and share new
features.
Taken from: FreeBSD SVN 232831 (2012-03-11)
One key difference between the DragonFly and FreeBSD implementations is
that FreeBSD will not properly execute a binary that requires
initialization and/or finalization if the PT_NOTE program header is
intentionally omitted using a custom linker script and the PHDRS
directive. In the same case, DragonFly will look to see if the main
binary contains a gnu hash dynamic tag. If it does, it assumes the binary
was built with the new crt, which is a very good assumption. Since gnu
hash was inserted by default into binaries only a week ago, there's only
a window of few days where this isn't true, and PT_NOTE-free binaries are
very rare.
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| 0e63a289 | 21-Jan-2012 |
John Marino <draco@marino.st> |
rtld: Add STT_GNU_IFUNC and R_MACHINE_IRELATIVE_GNU support
Add support for STT_GNU_IFUNC and R_MACHINE_IRELATIVE GNU extensions to
rtld. This adds runtime bits neccessary for the use of the dispatc
rtld: Add STT_GNU_IFUNC and R_MACHINE_IRELATIVE_GNU support
Add support for STT_GNU_IFUNC and R_MACHINE_IRELATIVE GNU extensions to
rtld. This adds runtime bits neccessary for the use of the dispatch
functions from the dynamically-linked executables and shared libraries.
To allow use of external references from the dispatch function, resolution
of the R_MACHINE_IRESOLVE relocations in PLT is postponed until GOT entries
for PLT are prepared, and normal resolution of the GOT entries is finished.
Similar to how it is done by GNU, IRELATIVE relocations are resolved in
advance, instead of normal lazy handling for PLT.
Taken-from:
FreeBSD SVN 228435 (12 DEC 2011)
FreeBSD SVN 228503 (14 DEC 2011)
FreeBSD SVN 229508 (04 JAN 2012)
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| e9de6dcc | 21-Jan-2012 |
John Marino <draco@marino.st> |
rtld: Add stubs to support PT_GNU_STACK
This functionality requires kernel support to determine the initial stack
access mode. This is how it's supposed to work:
If the loaded DSO requires an exec
rtld: Add stubs to support PT_GNU_STACK
This functionality requires kernel support to determine the initial stack
access mode. This is how it's supposed to work:
If the loaded DSO requires an executable stack as specified by the PF_X
bit or p_flags on PT_GNU_STACK phdr, yet the current stack protection does
not permit execution: The map_stacks_exec function should change the
stack protection mode of all thread stacks.
The PT_GNU_STACK phdr parser has been implemented as well as a private
interface to _rtld_get_stack_prot() in order to export the stack access
mode calculated by rtld.
Left to do:
1) Implement stack protection in the kernel
2) Add PT_GNU_STACK functionality in the kernel
3) Add a method to change stack protection mode in libc or libthread
4) Implement map_stacks_exec function in rtld.
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| 1c2e3f3c | 14-Jan-2012 |
John Marino <draco@marino.st> |
rtld: remove broken functionality to build exec. version
If anyone had tried to build an executable version of the dynamic linker
using the source makefiles, it would have failed. The i386 version
rtld: remove broken functionality to build exec. version
If anyone had tried to build an executable version of the dynamic linker
using the source makefiles, it would have failed. The i386 version had
bad CFLAGS and the x86_64 was missing the ldscript. Moreever, as the
gold linker doesn't use ldscripts, it was GNU linker (ld.bfd) specific.
If somebody decides this functionality is still desired, the ldscript
files from FreeBSD (elf_rtld.x) can be imported from FreeBSD likely
without modification. The now-dummy makefiles were alterated with
similar comments.
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