return from signal
() allows users to atomically
unmask, switch stacks, and return from a signal context. The processes signal
mask and stack status are restored from the context. The system call does not
return; the users stack pointer, frame pointer, argument pointer, and
processor status longword are restored from the context. Execution resumes at
the specified pc. This system call is used by the trampoline code and
returning from a signal to the previously executing program.
Note that sigcontext contains machine dependent information.
This system call is not available in 4.2BSD
should not be used if backward compatibility is needed.
If successful, the system call does not return. Otherwise, a value of -1 is
returned and errno
is set to indicate the
() will fail and the process context
will remain unchanged if one of the following occurs.
- scp points to memory that is not a valid
part of the process address space.
- The process status longword is invalid or would improperly raise the
privilege level of the process.
() function call appeared in