diff options
authorRich Felker <>2016-04-01 20:10:19 +0000
committerRich Felker <>2016-06-03 03:31:18 +0000
commit617bb6e1333957085e3ad28db9cac8bae209aed2 (patch)
parentdb28b1d8baf986cbaa6f752e92758ff262d5a921 (diff)
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 <>
1 files changed, 0 insertions, 3 deletions
diff --git a/arch/sh/include/uapi/asm/sigcontext.h b/arch/sh/include/uapi/asm/sigcontext.h
index 8ce1435bc0bf..faa5d0833412 100644
--- a/arch/sh/include/uapi/asm/sigcontext.h
+++ b/arch/sh/include/uapi/asm/sigcontext.h
@@ -25,8 +25,6 @@ struct sigcontext {
unsigned long sc_mach;
unsigned long sc_macl;
-#if defined(__SH4__) || defined(CONFIG_CPU_SH4) || \
- defined(__SH2A__) || defined(CONFIG_CPU_SH2A)
/* FPU registers */
unsigned long sc_fpregs[16];
unsigned long sc_xfpregs[16];
@@ -34,7 +32,6 @@ struct sigcontext {
unsigned int sc_fpul;
unsigned int sc_ownedfp;
#endif /* __ASM_SH_SIGCONTEXT_H */