diff options
Diffstat (limited to 'sys/ia64/include/ucontext.h')
| -rw-r--r-- | sys/ia64/include/ucontext.h | 49 |
1 files changed, 19 insertions, 30 deletions
diff --git a/sys/ia64/include/ucontext.h b/sys/ia64/include/ucontext.h index 0ff1e29f80b74..5619d59068c9a 100644 --- a/sys/ia64/include/ucontext.h +++ b/sys/ia64/include/ucontext.h @@ -45,48 +45,42 @@ * call to the function that creates the context. An asynctx needs to have the * scratch registers preserved because it can describe any point in a thread's * (or process') execution. + * The second variation is for synchronous contexts. When the kernel creates + * a synchronous context if needs to preserve the scratch registers, because + * the syscall argument and return values are stored there in the trapframe + * and they need to be preserved in order to restart a syscall or return the + * proper return values. Also, the IIP and CFM fields need to be preserved + * as they point to the syscall stub, which the kernel saves as a favor to + * userland (it keeps the stubs small and simple). * * Below a description of the flags and their meaning: * * _MC_FLAGS_ASYNC_CONTEXT * If set, indicates that mc_scratch and mc_scratch_fp are both - * valid. IFF not set, _MC_FLAGS_RETURN_VALID indicates if the - * return registers are valid or not. + * valid. IFF not set, _MC_FLAGS_SYSCALL_CONTEXT indicates if the + * synchronous context is one corresponding to a syscall or not. + * Only the kernel is expected to create such a context and it's + * probably wise to let the kernel restore it. * _MC_FLAGS_HIGHFP_VALID * If set, indicates that the high FP registers (f32-f127) are * valid. This flag is very likely not going to be set for any * sensible synctx, but is not explicitly disallowed. Any synctx * that has this flag may or may not have the high FP registers * restored. In short: don't do it. - * _MC_FLAGS_KSE_SET_MBOX - * This flag is special to setcontext(2) and swapcontext(2). It - * instructs the kernel to write the value in mc_special.isr to - * the memory address pointed to by mc_special.ifa. This allows - * the kernel to switch to a new context in a KSE based threaded - * program. Note that this is a non-srandard extension to the - * otherwise standard system calls and use of this flag should be - * limited to KSE. - * _MC_FLAGS_RETURN_VALID - * If set and _MC_FLAGS_ASYNC_CONTEXT is not set indicates that - * the ABI defined return registers are valid. Both getcontext(2) - * and swapcontext(2) need to save the system call return values. - * Any synctx that does not have this flag may still have the - * return registers restored from the context. - * _MC_FLAGS_SCRATCH_VALID - * If set and _MC_FLAGS_ASYNC_CONTEXT is not set indicates that - * the scratch registers, but not the FP registers are valid. - * This flag is set in contexts passed to signal handlers. This - * flag is a superset of _MC_FLAGS_RETURN_VALID. If both flags - * are set, this flag takes precedence. + * _MC_FLAGS_SYSCALL_CONTEXT + * If set (hence _MC_FLAGS_ASYNC_CONTEXT is not set) indicates + * that the scratch registers contain syscall arguments and + * return values and that additionally IIP and CFM are valid. + * Only the kernel is expected to create such a context. It's + * probably wise to let the kernel restore it. */ typedef struct __mcontext { unsigned long mc_flags; #define _MC_FLAGS_ASYNC_CONTEXT 0x0001 #define _MC_FLAGS_HIGHFP_VALID 0x0002 -#define _MC_FLAGS_KSE_SET_MBOX 0x0004 -#define _MC_FLAGS_RETURN_VALID 0x0008 -#define _MC_FLAGS_SCRATCH_VALID 0x0010 +#define _MC_FLAGS_KSE_SET_MBOX 0x0004 /* Undocumented. Has to go. */ +#define _MC_FLAGS_SYSCALL_CONTEXT 0x0008 unsigned long _reserved_; struct _special mc_special; struct _callee_saved mc_preserved; @@ -96,9 +90,4 @@ typedef struct __mcontext { struct _high_fp mc_high_fp; } mcontext_t; -#ifdef _KERNEL -/* Flags for get_mcontext(). See also <sys/ucontext.h>. */ -#define GET_MC_IA64_SCRATCH 0x10 -#endif - #endif /* !_MACHINE_UCONTEXT_H_ */ |