for TLS microbenchmark using global-dynamic TLS model on amd64 (which is
default for PIC dso objects).
Split the slow path into tls_get_addr_slow(), for which inlining is
disabled. This prevents the registers spill on tls_get_addr_common()
entry.
Provide static branch hint to the compiler, indicating that slow path
is not likely to be taken.
While there, do some minimal style adjustments.
Reported and tested by: davidxu
MFC after: 1 week
relocations until tls is initialized and stacks permissions correctly
set. This allows the ifunc to call malloc(3) and some other heavy
services.
Add debug banner.
MFC after: 3 days
from the dispatcher would also acquire bind lock in read mode, which
is the supported operation. plt is explicitely designed to allow safe
multithreaded updates, so the shared lock do not cause problems.
The error in r228435 is that it allows read lock acquisition after the
write lock for the bind block. If we dlopened the shared object that
contains IRELATIVE or jump slot which target is STT_GNU_IFUNC, then
possible recursive plt resolve from the dispatcher would cause it.
Postpone the resolution for irelative/ifunc right before initializers
are called, and drop bind lock around calls to dispatcher. Use
initlist to iterate over the objects instead of the ->next, due to
drop of the bind lock in iteration.
For i386/reloc.c:reloc_iresolve(), fix calculation of the dispatch
function address for dso, by taking into account possible non-zero
relocbase.
MFC after: 3 weeks
rtld on 386 and amd64. 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.
Move the init_pltgot() call before the relocations for the object are
processed.
MFC after: 3 weeks
relocations are processed, since tls initialization section might be
itself subject for relocations. Only set up of the block is postponed,
the tls block offsets are allocated before relocation processing, since
TLS-related relocations may need offsets ready.
Reported by: ale
PR: threads/161344
Reviewed by: kan
MFC after: 1 week
function (a hook necessary for gdb support), is inlined, but since the
function contains no code, no calls to it are generated. When gdb is
debugging a dynamically linked program, this causes backtraces to be
corrupted.
Fix it by marking the function __noinline, and inserting an empty asm
statement, that pretends to clobber memory. This forces the compiler to
emit calls to r_debug_state() throughout rtld.c.
Approved by: re (kib)
C runtime services, like printf(). Unfortunately, the multithread-safeness
measures in the libc do not work in rtld environment.
Rip the kernel printf() implementation and use it in the rtld instead of
libc version. This printf does not require any shared global data and thus
is mt-safe. Systematically use rtld_printf() and related functions, remove
the calls to err(3).
Note that stdio is still pulled from libc due to libmap implementaion using
fopen(). This is safe but unoptimal, and can be changed later.
Reported and tested by: pgj
Diagnosed and reviewed by: kan (previous version)
Approved by: re (bz)
The second close(2) call resulted in heisenbugs in some multi-threaded
applications where e.g. dlopen(3) call in one thread could close a file
descriptor for a file having been opened in other thread concurrently.
My litmus test for this issue was an openoffice.org build.
Reviewed by: jhb
MFC after: 2 weeks
Instead of aborting in locate_dependency(), propagate the error to
caller. The rtld startup function does the right thing with an error
from rtld_verify_versions(), depending on the mode of operation.
Reported by: maho
In collaboration with: kan
MFC after: 1 week
Place elements on DAG lists in breadth-first order. This allows us to
walk pre-built list in all cases where breadth-first dependency chain
enumeration is required.
Fix dlsym on special handle obtained by dlopen(NULL, ...) to do what
comment claims it does. Take advantage of recently added symlook_global
function to iterate over main objects and global DAGs lists properly in
search of a symbol. Since rtld itself provides part of the global
namespace, search rtld_obj too.
Remove recursion from init_dag and symlook_needed functions. Use
symlook_needed for ELF filtee processing only and change lookup order
used in the function to match the order used by Solaris runtime linker
under same circumstances. While there, fix weak symbol handling in the
loop so that we return the first weak symbol definition if no strong one
was found, instead of the last one.
Reviewed by: kib
MFC after: 1 month
one. Search global objects, together with main object and
dependencies, for the requested symbol.
Move the common code from symlook_default() into new helper
symlook_global(), and use it both in symlook_global() and
get_program_var_addr().
Supply lock state to get_program_var_addr().
Reviewed by: kan
Tested by: Mykola Dzham <i levsha me>
by kernel, and parse PT_GNU_STACK phdr from linked and loaded dsos.
If the loaded dso requires executable stack, as specified by PF_X bit
of p_flags of PT_GNU_STACK phdr, but current stack protection does not
permit execution, the __pthread_map_stacks_exec symbol is looked up
and called. It should be implemented in libc or threading library and
change the protection mode of all thread stacks to be executable.
Provide a private interface _rtld_get_stack_prot() to export the stack
access mode as calculated by rtld.
Reviewed by: kan
filters are implemented.
Filtees are loaded on demand, unless LD_LOADFLTR environment variable
is set or -z loadfltr was specified during the linking. This forces
rtld to upgrade read-locked rtld_bind_lock to write lock when it
encounters an object with filter during symbol lookup.
Consolidate common arguments of the symbol lookup functions in the
SymLook structure. Track the state of the rtld locks in the
RtldLockState structure. Pass local RtldLockState through the rtld
symbol lookup calls to allow lock upgrades.
Reviewed by: kan
Tested by: Mykola Dzham <i levsha me>, nwhitehorn (powerpc)
dlclose() call may unload the object of the outer call prematurely
because objects are unreferenced before _fini() calls.
Fix this by unreferencing objects after calling objlist_call_fini() in
dlclose(). Therefore objlist_call_fini() now calls the fini function if
the reference count of an object is 1. In addition we must restart the
list_fini traversal after every _fini() call because another dlclose()
call might have modified the reference counts.
Add an XXX comment to objlist_call_fini() about possible race with
dlopen().
PR: 133246, 149464
Reviewed by: kan, kib
loaded as a dependency and marked -z nodlopen, object' DAG is already
initialized by load_needed_objects(). Due to this, the init_dag() call
from dlopen() does not increment refcount for the object [1].
Change init_dag() to not increment DAG refcount. Require explicit calls
to ref_dag() to increment, and assert that ref_dag() and unref_dag()
are called for root that has dag initialized. To fix the noted issue,
unconditionally call both init_dag() and ref_dag() in dlopen() for the
case when the object was already loaded, making it similar to the case
of newly loaded object.
Noted by: jh [1]
Reviewed by: jh, kan
MFC after: 6 days
dependency, then the dso never has its DAG initialized. Empty DAG
makes ref_dag() call in dlopen() a nop, and the dso refcount is off
by one.
Initialize the DAG on the first dlopen() call, using a boolean flag
to prevent double initialization.
From the PR (edited):
Assume we have a library liba.so, containing a function a(), and a
library libb.so, containing function b(). liba.so needs functionality
from libb.so, so liba.so links in libb.so.
An application doesn't know about the relation between these libraries,
but needs to call a() and b(). It dlopen()s liba.so and obtains a
pointer to a(), then it dlopen()s libb.so and obtains a pointer to b().
As soon as the application doesn't need a() anymore, it dlclose()s liba.so.
Expected result: the pointer to b() is still valid and can be called
Actual result: the pointer to b() has become invalid, even though the
application did not dlclose() the handle to libb.so. On calling b(), the
application crashes with a segmentation fault.
PR: misc/151861
Based on patch by: jh
Reviewed by: kan
Tested by: Arjan van Leeuwen <freebsd-maintainer opera com>
MFC after: 1 week
atexit and __cxa_atexit handlers that are either installed by unloaded
dso, or points to the functions provided by the dso.
Use _rtld_addr_phdr to locate segment information from the address of
private variable belonging to the dso, supplied by crtstuff.c. Provide
utility function __elf_phdr_match_addr to do the match of address against
dso executable segment.
Call back into libthr from __cxa_finalize using weak
__pthread_cxa_finalize symbol to remove any atfork handler which
function points into unloaded object.
The rtld needs private __pthread_cxa_finalize symbol to not require
resolution of the weak undefined symbol at initialization time. This
cannot work, since rtld is relocated before sym_zero is set up.
Idea by: kan
Reviewed by: kan (previous version)
MFC after: 3 weeks
Use local version of getpagesize(), rtld_getpagesize() in private allocator.
Override the __getosreldate() previously fetched from libc_pic.a with
local version that uses aux value if present. Note that __getosreldate()
is used by rtld indirectly, by mmap(2) libc wrapper.
To be able to utilize aux, split digest_dynamic() for use by init_rtld()
into two parts, where the first one does not call malloc(), and the
second part uses it. init_rtld() is able to initialize global variables
before digest_dynamic2() calls. In particular, pagesize and osreldate are
set up from the aux values.
Now, rtld avoids (two) sysctl calls in startup.
Tested by: marius (sparc64)
MFC after: 1 month
fix for it.
The bug occurs when using the --as-needed flag to ld in the presence of
synthetic linker-generated symbols that reference symbols defined in
linked-to shared libraries with versioned symbols. When the only symbols
used from a library fall into this category, ld will drop the DT_NEEDED
entry for it, but retain the versioning information. This bug is best
fixed/hacked around in binutils, not in rtld.
Discussed with: kan
because calling mmap() etc. may use GOT which is not set up
yet. Use calloc() instead of mmap() in cases where this
was the case before (sparc64, powerpc, arm).
Submitted by: Dimitry Andric (dimitry andric com)
Reviewed by: kan
Approved by: ed (mentor)
o Use obj->tlsinitsize to determine whether there's initialized data.
o If obj->tlssize > obj->tlsinitsize, then bzero uninitialized data.
o Don't exclude variant I from the work-around in free_tls_offset().
adjustment for all virtual addresses encoded into the ELF structures of
it. PIE binary could and should be loaded at non-zero mapbase.
For sym_zero pseudosymbol used as a return value from find_symdef()
for undefined weak symbols, st_value also should be adjusted, since
_rtld_bind corrects symbol values by relocbase.
Discussed with: bz
Reviewed by: kan
Tested by: bz (i386, amd64), bsam (linux)
MFC after: some time
