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)

2 files changed, 16 insertions, 6 deletions

diff --git a/sys/pc98/i386/machdep.c b/sys/pc98/i386/machdep.c
index 707b8fc7d3aa..b9013a22da35 100644
--- a/sys/pc98/i386/machdep.c
+++ b/sys/pc98/i386/machdep.c
@@ -2428,7 +2428,7 @@ set_fpregs(struct thread *td, struct fpreg *fpregs)
  * Get machine context.
  */
 int
-get_mcontext(struct thread *td, mcontext_t *mcp)
+get_mcontext(struct thread *td, mcontext_t *mcp, int clear_ret)
 {
 	struct trapframe *tp;
 
@@ -2446,9 +2446,14 @@ get_mcontext(struct thread *td, mcontext_t *mcp)
 	mcp->mc_ebp = tp->tf_ebp;
 	mcp->mc_isp = tp->tf_isp;
 	mcp->mc_ebx = tp->tf_ebx;
-	mcp->mc_edx = tp->tf_edx;
+	if (clear_ret != 0) {
+		mcp->mc_eax = 0;
+		mcp->mc_edx = 0;
+	} else {
+		mcp->mc_eax = tp->tf_eax;
+		mcp->mc_edx = tp->tf_edx;
+	}
 	mcp->mc_ecx = tp->tf_ecx;
-	mcp->mc_eax = tp->tf_eax;
 	mcp->mc_eip = tp->tf_eip;
 	mcp->mc_cs = tp->tf_cs;
 	mcp->mc_eflags = tp->tf_eflags;
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index 707b8fc7d3aa..b9013a22da35 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -2428,7 +2428,7 @@ set_fpregs(struct thread *td, struct fpreg *fpregs)
  * Get machine context.
  */
 int
-get_mcontext(struct thread *td, mcontext_t *mcp)
+get_mcontext(struct thread *td, mcontext_t *mcp, int clear_ret)
 {
 	struct trapframe *tp;
 
@@ -2446,9 +2446,14 @@ get_mcontext(struct thread *td, mcontext_t *mcp)
 	mcp->mc_ebp = tp->tf_ebp;
 	mcp->mc_isp = tp->tf_isp;
 	mcp->mc_ebx = tp->tf_ebx;
-	mcp->mc_edx = tp->tf_edx;
+	if (clear_ret != 0) {
+		mcp->mc_eax = 0;
+		mcp->mc_edx = 0;
+	} else {
+		mcp->mc_eax = tp->tf_eax;
+		mcp->mc_edx = tp->tf_edx;
+	}
 	mcp->mc_ecx = tp->tf_ecx;
-	mcp->mc_eax = tp->tf_eax;
 	mcp->mc_eip = tp->tf_eip;
 	mcp->mc_cs = tp->tf_cs;
 	mcp->mc_eflags = tp->tf_eflags;