The current getcontext return trampoline is overly complex and it
unnecessarily clobbers several registers. By saving the context
pointer (r26) in the context, __getcontext_ret can restore any
registers not restored by setcontext. This allows getcontext to
save and restore the entire register context present when getcontext
is entered. We use the unused oR0 context slot for the return
from __getcontext_ret.
While this is not directly useful in C, it can be exploited in
assembly code. Registers r20, r23, r24 and r25 are not clobbered
in the call path to getcontext. This allows a small simplification
of swapcontext.
It also allows saving and restoring the 6-bit SAR register in the
LSB of the oSAR context slot. The getcontext flag value can be
stored in the MSB of the oSAR slot.
This change fixes the failure of stdlib/tst-setcontext2 and
stdlib/tst-setcontext7 on hppa. The implementation of swapcontext
in C is broken. C saves the return pointer (rp) and any non
call-clobbered registers (in this case r3, r4 and r5) on the
stack. However, the setcontext call in swapcontext pops the
stack and subsequent calls clobber the saved registers. When
the context in oucp is restored, both tests fault.
Here we rewrite swapcontext in assembly code to avoid using
the stack for register values that need to be used after
restoration. The getcontext and setcontext routines are
revised to save and restore register ret1 for normal returns.
We copy the oucp pointer to ret1. This allows access to
the old context after calling getcontext and setcontext.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date. Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.
Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions. These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.
The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively. These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:
https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dchttps://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
When adding/updating localplt.data for various architectures to get
the compilation tests passing everywhere, I generally made it reflect
the existing state of what local PLT entries were actually seen,
rather than an ideal state with as few as possible such entries,
mainly for functions that are intended to be interposable.
This patch eliminates some local PLT entries for hppa by using
__sigprocmask instead of sigprocmask in getcontext and setcontext.
The specific case of sigprocmask called by setcontext is the third of
four items in bug 18124 (the other three have already been fixed for
2.26 or earlier releases). Note that hppa-specific localplt.data
entries for __sigsetjmp, _IO_funlockfile and __errno_location remain,
but the causes / fixes are less immediately obvious from source
inspection.
Tested (compilation tests only) with build-many-glibcs.py for
hppa-linux-gnu.
[BZ #18124]
* sysdeps/hppa/bsd-setjmp.S: Include <sysdep.h>.
(setjmp): Use HIDDEN_JUMPTARGET with __sigsetjmp.
* sysdeps/unix/sysv/linux/hppa/getcontext.S (__getcontext): Call
__sigprocmask instead of sigprocmask.
* sysdeps/unix/sysv/linux/hppa/setcontext.S (__setcontext):
Likewise.
* sysdeps/unix/sysv/linux/hppa/localplt.data: Remove entries for
__sigsetjmp and sigprocmask.
__setcontext on hppa.
* sysdeps/unix/sysv/linux/hppa/getcontext.S (__getcontext): Save return
pointer in frame.
* sysdeps/unix/sysv/linux/hppa/setcontext.S (__setcontext): Likewise.
Correct offset used to restore PIC register.
There appears to be a discrepancy among the implementations
of setcontext with regards to the function called once the last
linked-to context has finished executing via setcontext.
The POSIX standard says:
~~~
If the uc_link member of the ucontext_t structure pointed to by
the ucp argument is equal to 0, then this context is the main
context, and the thread will exit when this context returns.
~~~
It says "exit" not "exit immediately" nor "exit without running
functions registered with atexit or on_exit."
Therefore the AArch64, ARM, hppa and NIOS II implementations are
wrong and no test detects it.
It is questionable if this should even be fixed or just documented
that the above 4 targets are wrong. The functions are deprecated
and nobody should be using them, but at the same time it silly to
have cross-target differences that make it hard to port old
applications from say x86_64 to AArch64.
Therefore I will ix the 4 arches, and checkin a regression
test to prevent it from changing again.
https://sourceware.org/ml/libc-alpha/2015-03/msg00720.html
