diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/powerpc/sys')
| -rw-r--r-- | sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h b/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h index 9ce93c8197..4bb8bb26d0 100644 --- a/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h +++ b/sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h @@ -74,14 +74,40 @@ typedef struct ucontext struct ucontext *uc_link; stack_t uc_stack; #if __WORDSIZE == 32 - /* These fields are for backwards compatibility. */ + /* + * These fields are set up this way to maximize source and + * binary compatibility with code written for the old + * ucontext_t definition, which didn't include space for the + * registers. + * + * Different versions of the kernel have stored the registers on + * signal delivery at different offsets from the ucontext struct. + * Programs should thus use the uc_mcontext.uc_regs pointer to + * find where the registers are actually stored. The registers + * will be stored within the ucontext_t struct but not necessarily + * at a fixed address. As a side-effect, this lets us achieve + * 16-byte alignment for the register storage space if the + * Altivec registers are to be saved, without requiring 16-byte + * alignment on the whole ucontext_t. + * + * The uc_mcontext.regs field is included for source compatibility + * with programs written against the older ucontext_t definition, + * and its name should therefore not change. The uc_pad field + * is for binary compatibility with programs compiled against the + * old ucontext_t; it ensures that uc_mcontext.regs and uc_sigmask + * are at the same offset as previously. + */ int uc_pad[7]; - mcontext_t *uc_regs; - unsigned int uc_oldsigmask[2]; - int uc_pad2; -#endif + union uc_regs_ptr { + struct pt_regs *regs; + mcontext_t *uc_regs; + } uc_mcontext; + sigset_t uc_sigmask; + char uc_reg_space[sizeof(mcontext_t) + 12]; /* last for extensibility */ +#else /* 64-bit */ sigset_t uc_sigmask; mcontext_t uc_mcontext; /* last for extensibility */ +#endif } ucontext_t; #endif /* sys/ucontext.h */ |