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Revert "MIPS: Save/restore MSA context around signals"

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This reverts commit eec43a224c "MIPS: Save/restore MSA context around
signals" and the MSA parts of ca750649e0 "MIPS: kernel: signal:
Prevent save/restore FPU context in user memory" (the restore path of
which appears incorrect anyway...).

The reverted patch took care not to break compatibility with userland
users of struct sigcontext, but inadvertantly changed the offset of the
uc_sigmask field of struct ucontext. Thus Linux v3.15 breaks the
userland ABI. The MSA context will need to be saved via some other
opt-in mechanism, but for now revert the change to reduce the fallout.

This will have minimal impact upon use of MSA since the only supported
CPU which includes it (the P5600) is 32-bit and therefore requires that
the experimental CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option be selected
before the kernel will set FR=1 for a task, a requirement for MSA use.
Thus the users of MSA are limited to known small groups of people & this
patch won't be breaking any previously working MSA-using userland
outside of experimental settings.

[ralf@linux-mips.org: Fixed rejects.]

Cc: stable@vger.kernel.org
Reported-by: Joseph S. Myers <joseph@codesourcery.com>
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7107/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2014-06-18 15:00:46 +01:00 • committed by Ralf Baechle
parent fb738f8544
commit 16f77de82f
6 changed files with 16 additions and 363 deletions
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2
arch/mips/include/asm/sigcontext.h
View file

@ -32,8 +32,6 @@ struct sigcontext32 {
__u32 sc_lo2;
__u32 sc_hi3;
__u32 sc_lo3;
__u64 sc_msaregs[32]; /* Most significant 64 bits */
__u32 sc_msa_csr;
};
#endif /* _MIPS_SIM == _MIPS_SIM_ABI64 || _MIPS_SIM == _MIPS_SIM_NABI32 */
#endif /* _ASM_SIGCONTEXT_H */