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71c01af52f
* Since __fentry__ is almost the same as _mcount, reuse the code by #including it twice with different #defines around. * Remove LA usages - they are needed in 31-bit mode to clear the top bit, but in 64-bit they appear to do nothing. * Add CFI rule for the nonstandard return register. This rule applies to the current function (binutils generates a new CIE - see gas/dw2gencfi.c:select_cie_for_fde()), so it is not necessary to put __fentry__ into a new file. * Fix CFI offset for %r14. * Add CFI rule for %r0. * Fix unwound value of %r15 being off by 244 bytes. * Unwinding in __fentry__@plt does not work, no plan to fix it - it would require asking linker to generate CFI for return address in %r0. From functional perspective keeping it broken is fine, since the callee did not have a chance to do anything yet. From convenience perspective it would be possible to enhance GDB in the future to treat __fentry__@plt in a special way. * Fix whitespace. * Fix offsets in comments, which were copied from 32-bit code. * 32-bit version will not be implemented, since it's not compatible with the corresponding PLT stubs: they assume %r12 points to GOT, which is not the case for gcc-emitted __fentry__ stub, which runs before the prolog. This patch adds the runtime support in glibc for the -mfentry gcc feature introduced in [1] and [2]. [1] https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00784.html [2] https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00912.html ChangeLog: * sysdeps/s390/s390-64/Versions (__fentry__): Add. * sysdeps/s390/s390-64/s390x-mcount.S: Move the common code to s390x-mcount.h and #include it. * sysdeps/s390/s390-64/s390x-mcount.h: New file. * sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist (__fentry__): Add. |
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