Add an argument to get_mcontext() which specified whether the

syscall return values should be cleared.  The system calls
getcontext() and swapcontext() want to return 0 on success
but these contexts can be switched to at a later time so
the return values need to be cleared in the saved register
sets.  Other callers of get_mcontext() would normally want
the context without clearing the return values.

Remove the i386-specific context saving from the KSE code.
get_mcontext() is not i386-specific any more.

Fix a bad pointer in the alpha get_mcontext() code.  The
context was being bcopy()'d from &td->tf_frame, but tf_frame
is itself a pointer, so the thread was being copied instead.
Spotted by jake.

Glanced at by:  jake
Reviewed by:    bde (months ago)

1 files changed, 7 insertions, 3 deletions

diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index c7e8c8c..1efc6b9 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -1977,13 +1977,17 @@ set_regs(td, regs)
 }
 
 int
-get_mcontext(struct thread *td, mcontext_t *mcp)
+get_mcontext(struct thread *td, mcontext_t *mcp, int clear_ret)
 {
 	/*
 	 * Use a trapframe for getsetcontext, so just copy the
 	 * threads trapframe.
 	 */
-	bcopy(&td->td_frame, &mcp->mc_regs, sizeof(td->td_frame));
+	bcopy(td->td_frame, &mcp->mc_regs, sizeof(struct trapframe));
+	if (clear_ret != 0) {
+		mcp->mc_regs[FRAME_V0] = 0;
+		mcp->mc_regs[FRAME_A4] = 0;
+	}
 
 	/*
 	 * When the thread is the current thread, the user stack pointer
@@ -2029,7 +2033,7 @@ set_mcontext(struct thread *td, const mcontext_t *mcp)
 		 * The context is a trapframe, so just copy it over the
 		 * threads frame.
 		 */
-		bcopy(&mcp->mc_regs, &td->td_frame, sizeof(td->td_frame));
+		bcopy(&mcp->mc_regs, td->td_frame, sizeof(struct trapframe));
 	}
 	return (0);
 }