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sh: make sigcontext definition consistent across fpu/nofpu models
Up until now, the SH version of the sigcontext structure, and thus mcontext_t/ucontext_t, varied depending on the cpu model the kernel was built to run on. SH-4 (including SH-4A) and SH-2A used the form with space for FPU registers, and everything else used a form that omitted them. From a userspace perspective, however, the structure layout must be fixed for a given ABI. Traditionally glibc and uClibc used the form with space for FPU registers only when __SH4__ (which implies FPU; __SH4_NOFPU__ is the predefined macro for SH-4 but with no-FPU ABI) was defined. As a result: - SH-4 no-FPU programs never matched kernel sigcontext. - SH-3 programs did not match kernel sigcontext if run on SH-4, despite an apparent intent that they be compatible. - SH-2 and SH-2A programs (using uClibc) did not match kernel sigcontext if run on SH-2A. The mismatch might seem inconsequential because it occurs at the end of the sigcontext structure, but sigcontext is embedded as uc_mcontext in ucontext_t, where it is followed by uc_sigmask, an important member for signal handlers to have access to. In particular, access to uc_sigmask is necessary for a correct implementation of thread cancellation. It would be possible to retain support for both sigcontext ABIs via a personality mechanism, but since many configurations were already broken and nobody noticed, and since there are very few if any users of legacy no-FPU models anymore, I have opted to just remove the variation and always include space for the FPU registers in sigcontext. This was proposed and discussed on a thread "SH sigcontext ABI is broken" cross-posted to linux-sh, libc-alpha, and musl libc lists in June 2015, and no objections were raised. Signed-off-by: Rich Felker <dalias@libc.org>
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1 changed files with 0 additions and 3 deletions
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@ -25,8 +25,6 @@ struct sigcontext {
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unsigned long sc_mach;
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unsigned long sc_mach;
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unsigned long sc_macl;
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unsigned long sc_macl;
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#if defined(__SH4__) || defined(CONFIG_CPU_SH4) || \
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defined(__SH2A__) || defined(CONFIG_CPU_SH2A)
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/* FPU registers */
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/* FPU registers */
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unsigned long sc_fpregs[16];
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unsigned long sc_fpregs[16];
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unsigned long sc_xfpregs[16];
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unsigned long sc_xfpregs[16];
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@ -34,7 +32,6 @@ struct sigcontext {
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unsigned int sc_fpul;
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unsigned int sc_fpul;
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unsigned int sc_ownedfp;
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unsigned int sc_ownedfp;
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#endif
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#endif
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#endif
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};
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};
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#endif /* __ASM_SH_SIGCONTEXT_H */
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#endif /* __ASM_SH_SIGCONTEXT_H */
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