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2015-04-23fix misalignment of dtv in static-linked programs with odd-sized TLSRich Felker-1/+2
both static and dynamic linked versions of the __copy_tls function have a hidden assumption that the alignment of the beginning or end of the memory passed is suitable for storing an array of pointers for the dtv. pthread_create satisfies this requirement except when libc.tls_size is misaligned, which cannot happen with dynamic linking due to way update_tls_size computes the total size, but could happen with static linking and odd-sized TLS.
2015-04-23remove dead store from static __init_tlsRich Felker-2/+0
commit dab441aea240f3b7c18a26d2ef51979ea36c301c, which made thread pointer init mandatory for all programs, rendered this store obsolete by removing the early-return path for static programs with no TLS.
2015-04-23make __init_tp function static when static linkingRich Felker-0/+3
this slightly reduces the code size cost of TLS/thread-pointer for static linking since __init_tp can be inlined into its only caller and removed. this is analogous to the handling of __init_libc in __libc_start_main, where the function only has external linkage when it needs to be called from the dynamic linker.
2015-04-23fix regression in x86_64 math asm with old binutilsRich Felker-6/+6
the implicit-operand form of fucomip is rejected by binutils 2.19 and perhaps other versions still in use. writing both operands explicitly fixes the issue. there is no change to the resulting output. commit a732e80d33b4fd6f510f7cec4f5573ef5d89bc4e was the source of this regression.
2015-04-22minor optimization to pthread_spin_trylockRich Felker-2/+4
use CAS instead of swap since it's lighter for most archs, and keep EBUSY in the lock value so that the old value obtained by CAS can be used directly as the return value for pthread_spin_trylock.
2015-04-22optimize spin lock not to dirty cache line while spinningRich Felker-1/+1
2015-04-22in visibility preinclude, remove overrides for stdin/stdout/stderrRich Felker-3/+0
the motivation for this change is that the extra declaration (with or without visibility) using "struct _IO_FILE" instead of "FILE" seems to trigger a bug in gcc 3.x where it considers the types mismatched. however, this change also results in slightly better code and it is valid because (1) these three objects are constant, and (2) applying the & operator to any of them is invalid C, since they are not even specified to be objects. thus it does not matter if the application and libc see different addresses for them, as long as the (initial, unchanging) value is seen the same by both.
2015-04-22fix inconsistent visibility for __hwcap and __sysinfo symbolsRich Felker-5/+3
these are used as hidden by asm files (and such use is the whole reason they exist), but their actual definitions were not hidden.
2015-04-22remove additional libc struct accessor cruftRich Felker-12/+0
commit f9cccfc16e58b39ee381fbdfb8688db3bb8e3555 left behind the part in libc.c; remove it too.
2015-04-22remove useless visibility application from static-linking-only codeRich Felker-3/+2
part of the goal here is to eliminate use of the ATTR_LIBC_VISIBILITY macro outside of libc.h, since it was never intended to be 'public'.
2015-04-22remove libc.h dependency from otherwise-independent multibyte codeRich Felker-2/+4
2015-04-22remove cruft for libc struct accessor function and broken visibilityRich Felker-18/+0
these were hacks to work around toolchains that could not properly optimize PIC accesses based on visibility and would generate GOT lookups even for hidden data, which broke the old dynamic linker. since commit f3ddd173806fd5c60b3f034528ca24542aecc5b9 it no longer matters; the dynamic linker does not assume accessibility of this data until stage 3.
2015-04-21fix duplocale clobbering of new locale struct with memcpy of oldRich Felker-1/+2
when the non-stub duplocale code was added as part of the locale framework in commit 0bc03091bb674ebb9fa6fe69e4aec1da3ac484f2, the old code to memcpy the old locale object to the new one was left behind. the conditional for the memcpy no longer makes sense, because the conditions are now always-true when it's reached, and the memcpy is wrong because it clobbers the new->messages_name pointer setup just above. since the messages_name and ctype_utf8 members have already been copied, all that remains is the cat[] array. these pointers are volatile, so using memcpy to copy them is formally wrong; use a for loop instead.
2015-04-21remove dead case for F_SETLKW in fcntlRich Felker-1/+0
the first switch already returns in the F_SETLKW code path so it need not be handled in the second switch. moreover the code in the second switch is wrong for the F_SETLKW command: it's not cancellable.
2015-04-21fix mmap leak in sem_open failure path for link callRich Felker-0/+1
the leak was found by static analysis (reported by Alexander Monakov), not tested/observed, but seems to have occured both when failing due to O_EXCL, and in a race condition with O_CREAT but not O_EXCL where a semaphore by the same name was created concurrently.
2015-04-21remove always-true conditional in dynamic linker TLSDESC processingRich Felker-1/+1
the allocating path which can fail is for dynamic TLS, which can only occur at runtime, and the check for runtime was already made in the outer conditional.
2015-04-21remove redundant code in do_dlsym functionRich Felker-1/+1
commit 637dd2d383cc1f63bf02a732f03786857b22c7bd introduced the checks for RTLD_DEFAULT and RTLD_NEXT here, claiming they fixed a regression, but the above conditional block clearly already covered these cases, and removing the checks produces no difference in the generated code.
2015-04-19add optional global visibility overrideRich Felker-0/+40
this is implemented via the build system and does not affect source files. the idea is to use protected or hidden visibility to prevent the compiler from pessimizing function calls within a shared (or position-independent static) libc in the form of overhead setting up for a call through the PLT. the ld-time symbol binding via the -Bsymbolic-functions option already optimized out the PLT itself, but not the code in the caller needed to support a call through the PLT. on some archs this overhead can be substantial; on others it's trivial.
2015-04-19remove invalid PLT calls from or1k asmRich Felker-3/+7
analogous to commit 646cb9a4a04e5ed78e2dd928bf9dc6e79202f609 for sh.
2015-04-19remove possible-textrels from powerpc asmRich Felker-2/+6
these are perfectly fine with ld-time symbol binding, but otherwise result in textrels. they cannot be replaced with @PLT jump targets because the PLT thunks require a GOT register to be setup, so use a hidden alias instead.
2015-04-19remove invalid PLT calls from microblaze asmRich Felker-2/+6
analogous to commit 646cb9a4a04e5ed78e2dd928bf9dc6e79202f609 for sh.
2015-04-19remove invalid PLT calls from sh asmRich Felker-2/+6
these are perfectly fine with ld-time symbol binding, but if the calls go through a PLT thunk, they are invalid because the caller does not setup a GOT register. use a hidden alias to bypass the issue.
2015-04-18remove potentially PIC-incompatible relocations from x86_64 and x32 asmRich Felker-7/+11
analogous to commit 8ed66ecbcba1dd0f899f22b534aac92a282f42d5 for i386.
2015-04-18remove the last of possible-textrels from i386 asmRich Felker-4/+16
none of these are actual textrels because of ld-time binding performed by -Bsymbolic-functions, but I'm changing them with the goal of making ld-time binding purely an optimization rather than relying on it for semantic purposes. in the case of memmove's call to memcpy, making it explicit that the memmove asm is assuming the forward-copying behavior of the memcpy asm is desirable anyway; in case memcpy is ever changed, the semantic mismatch would be apparent while editing memmcpy.s.
2015-04-18make dlerror state and message thread-local and dynamically-allocatedRich Felker-32/+65
this fixes truncation of error messages containing long pathnames or symbol names. the dlerror state was previously required by POSIX to be global. the resolution of bug 97 relaxed the requirements to allow thread-safe implementations of dlerror with thread-local state and message buffer.
2015-04-18add missing 'void' in prototypes of internal pthread functionsAlexander Monakov-6/+6
2015-04-18math: fix pow(+-0,-inf) not to raise divbyzero flagSzabolcs Nagy-3/+3
this reverts the commit f29fea00b5bc72d4b8abccba2bb1e312684d1fce which was based on a bug in C99 and POSIX and did not match IEEE-754 http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1515.pdf
2015-04-17apply hidden visibility to tlsdesc accessor functionsRich Felker-0/+10
these functions are never called directly; only their addresses are used, so PLT indirections should never happen unless a broken application tries to redefine them, but it's still best to make them hidden.
2015-04-17comment fixes in aarch64 tlsdesc asmSzabolcs Nagy-4/+4
2015-04-17ensure debugger hook for dynamic linker does not point to a PLT slotRich Felker-2/+4
this change is made in preparation to support linking without -Bsymbolic-functions.
2015-04-17fix mips fesetenv(FE_DFL_ENV) againRich Felker-0/+1
commit 5fc1487832e16aa2119e735a388d5f36c8c139e2 attempted to fix it, but neglected the fact that mips has branch delay slots.
2015-04-17fix PLT call offset in sh dlsym asmRich Felker-3/+3
the braf instruction's destination register is an offset from the address of the braf instruction plus 4 (or equivalently, the address of the next instruction after the delay slot). the code for dlsym was incorrectly computing the offset to pass using the address of the delay slot itself. in other places, a label was placed after the delay slot, but I find this confusing. putting the label on the branch instruction itself, and manually adding 4, makes it more clear which branch the offset in the constant pool goes with.
2015-04-17fix sh build regressions in asmRich Felker-2/+2
even hidden functions need @PLT symbol references; otherwise an absolute address is produced instead of a PC-relative one.
2015-04-17fix sh __set_thread_area uninitialized return valueRich Felker-1/+2
this caused the dynamic linker/startup code to abort when r0 happened to contain a negative value.
2015-04-17redesign sigsetjmp so that signal mask is restored after longjmpRich Felker-133/+177
the conventional way to implement sigsetjmp is to save the signal mask then tail-call to setjmp; siglongjmp then restores the signal mask and calls longjmp. the problem with this approach is that a signal already pending, or arriving between unmasking of signals and restoration of the saved stack pointer, will have its signal handler run on the stack that was active before siglongjmp was called. this can lead to unbounded stack usage when siglongjmp is used to leave a signal handler. in the new design, sigsetjmp saves its own return address inside the extended part of the sigjmp_buf (outside the __jmp_buf part used by setjmp) then calls setjmp to save a jmp_buf inside its own execution. it then tail-calls to __sigsetjmp_tail, which uses the return value of setjmp to determine whether to save the current signal mask or restore a previously-saved mask. as an added bonus, this design makes it so that siglongjmp and longjmp are identical. this is useful because the __longjmp_chk function we need to add for ABI-compatibility assumes siglongjmp and longjmp are the same, but for different reasons -- it was designed assuming either can access a flag just past the __jmp_buf indicating whether the signal masked was saved, and act on that flag. however, early versions of musl did not have space past the __jmp_buf for the non-sigjmp_buf version of jmp_buf, so our setjmp cannot store such a flag without risking clobbering memory on (very) old binaries.
2015-04-14use hidden __tls_get_new for tls/tlsdesc lookup fallback casesRich Felker-5/+13
previously, the dynamic tlsdesc lookup functions and the i386 special-ABI ___tls_get_addr (3 underscores) function called __tls_get_addr when the slot they wanted was not already setup; __tls_get_addr would then in turn also see that it's not setup and call __tls_get_new. calling __tls_get_new directly is both more efficient and avoids the issue of calling a non-hidden (public API/ABI) function from asm. for the special i386 function, a weak reference to __tls_get_new is used since this function is not defined when static linking (the code path that needs it is unreachable in static-linked programs).
2015-04-14cleanup use of visibility attributes in pthread_cancel.cRich Felker-8/+9
applying the attribute to a weak_alias macro was a hack. instead use a separate declaration to apply the visibility, and consolidate declarations together to avoid having visibility mess all over the file.
2015-04-14fix inconsistent visibility for internal syscall symbolsRich Felker-1/+16
2015-04-14use hidden visibility for call from dlsym to internal __dlsymRich Felker-3/+14
2015-04-14consistently use hidden visibility for cancellable syscall internalsRich Felker-30/+96
in a few places, non-hidden symbols were referenced from asm in ways that assumed ld-time binding. while these is no semantic reason these symbols need to be hidden, fixing the references without making them hidden was going to be ugly, and hidden reduces some bloat anyway. in the asm files, .global/.hidden directives have been moved to the top to unclutter the actual code.
2015-04-14fix inconsistent visibility for internal __tls_get_new functionRich Felker-3/+3
at the point of call it was declared hidden, but the definition was not hidden. for some toolchains this inconsistency produced textrels without ld-time binding.
2015-04-14use hidden visibility for i386 asm-internal __vsyscall symbolRich Felker-0/+2
otherwise the call instruction in the inline syscall asm results in textrels without ld-time binding.
2015-04-14make _dlstart_c function use hidden visibilityRich Felker-0/+1
otherwise the call/jump from the crt_arch.h asm may not resolve correctly without -Bsymbolic-functions.
2015-04-13remove initializers for decoded aux/dyn arrays in dynamic linkerRich Felker-5/+5
the zero initialization is redundant since decode_vec does its own clearing, and it increases the risk that buggy compilers will generate calls to memset. as long as symbols are bound at ld time, such a call will not break anything, but it may be desirable to turn off ld-time binding in the future.
2015-04-13allow libc itself to be built with stack protector enabledRich Felker-0/+10
this was already essentially possible as a result of the previous commits changing the dynamic linker/thread pointer bootstrap process. this commit mainly adds build system infrastructure: configure no longer attempts to disable stack protector. instead it simply determines how so the makefile can disable stack protector for a few translation units used during early startup. stack protector is also disabled for memcpy and memset since compilers (incorrectly) generate calls to them on some archs to implement struct initialization and assignment, and such calls may creep into early initialization. no explicit attempt to enable stack protector is made by configure at this time; any stack protector option supported by the compiler can be passed to configure in CFLAGS, and if the compiler uses stack protector by default, this default is respected.
2015-04-13remove remnants of support for running in no-thread-pointer modeRich Felker-32/+13
since 1.1.0, musl has nominally required a thread pointer to be setup. most of the remaining code that was checking for its availability was doing so for the sake of being usable by the dynamic linker. as of commit 71f099cb7db821c51d8f39dfac622c61e54d794c, this is no longer necessary; the thread pointer is now valid before any libc code (outside of dynamic linker bootstrap functions) runs. this commit essentially concludes "phase 3" of the "transition path for removing lazy init of thread pointer" project that began during the 1.1.0 release cycle.
2015-04-13move thread pointer setup to beginning of dynamic linker stage 3Rich Felker-8/+23
this allows the dynamic linker itself to run with a valid thread pointer, which is a prerequisite for stack protector on archs where the ssp canary is stored in TLS. it will also allow us to remove some remaining runtime checks for whether the thread pointer is valid. as long as the application and its libraries do not require additional size or alignment, this early thread pointer will be kept and reused at runtime. otherwise, a new static TLS block is allocated after library loading has finished and the thread pointer is switched over.
2015-04-13stabilize dynamic linker's layout of static TLSRich Felker-9/+6
previously, the layout of the static TLS block was perturbed by the size of the dtv; dtv size increasing from 0 to 1 perturbed both TLS arch types, and the TLS-above-TP type's layout was perturbed by the specific number of dtv slots (libraries with TLS). this behavior made it virtually impossible to setup a tentative thread pointer address before loading libraries and keep it unchanged as long as the libraries' TLS size/alignment requirements fit. the new code fixes the location of the dtv and pthread structure at opposite ends of the static TLS block so that they will not move unless size or alignment changes.
2015-04-13allow i386 __set_thread_area to be called more than onceRich Felker-1/+5
previously a new GDT slot was requested, even if one had already been obtained by a previous call. instead extract the old slot number from GS and reuse it if it was already set. the formula (GS-3)/8 for the slot number automatically yields -1 (request for new slot) if GS is zero (unset).
2015-04-13dynamic linker bootstrap overhaulRich Felker-442/+338
this overhaul further reduces the amount of arch-specific code needed by the dynamic linker and removes a number of assumptions, including: - that symbolic function references inside libc are bound at link time via the linker option -Bsymbolic-functions. - that libc functions used by the dynamic linker do not require access to data symbols. - that static/internal function calls and data accesses can be made without performing any relocations, or that arch-specific startup code handled any such relocations needed. removing these assumptions paves the way for allowing libc.so itself to be built with stack protector (among other things), and is achieved by a three-stage bootstrap process: 1. relative relocations are processed with a flat function. 2. symbolic relocations are processed with no external calls/data. 3. main program and dependency libs are processed with a fully-functional libc/ldso. reduction in arch-specific code is achived through the following: - crt_arch.h, used for generating crt1.o, now provides the entry point for the dynamic linker too. - asm is no longer responsible for skipping the beginning of argv[] when ldso is invoked as a command. - the functionality previously provided by __reloc_self for heavily GOT-dependent RISC archs is now the arch-agnostic stage-1. - arch-specific relocation type codes are mapped directly as macros rather than via an inline translation function/switch statement.