Newer versions of gcc don't support treating structures passed by value

as if they were really passed by reference. Specifically, the dead stores
elimination pass in the GCC 4.1 optimiser breaks the non-compliant behavior
on which FreeBSD relied. This change brings FreeBSD up to date by switching
trap frames to being explicitly passed by reference.

Reviewed by: kan
Tested by: kan

2 files changed, 18 insertions, 17 deletions

diff --git a/sys/amd64/ia32/ia32_exception.S b/sys/amd64/ia32/ia32_exception.S
index c65634e..4820f53 100644
--- a/sys/amd64/ia32/ia32_exception.S
+++ b/sys/amd64/ia32/ia32_exception.S
@@ -61,6 +61,7 @@ IDTVEC(int0x80_syscall)
 	movq	%r14,TF_R14(%rsp)
 	movq	%r15,TF_R15(%rsp)
 	FAKE_MCOUNT(TF_RIP(%rsp))
+	movq	%rsp, %rdi
 	call	ia32_syscall
 	MEXITCOUNT
 	jmp	doreti
diff --git a/sys/amd64/ia32/ia32_syscall.c b/sys/amd64/ia32/ia32_syscall.c
index e007b3a..c51a2be 100644
--- a/sys/amd64/ia32/ia32_syscall.c
+++ b/sys/amd64/ia32/ia32_syscall.c
@@ -86,10 +86,10 @@ __FBSDID("$FreeBSD$");
 extern inthand_t IDTVEC(int0x80_syscall), IDTVEC(rsvd);
 extern const char *freebsd32_syscallnames[];
 
-void ia32_syscall(struct trapframe frame);	/* Called from asm code */
+void ia32_syscall(struct trapframe *frame);	/* Called from asm code */
 
 void
-ia32_syscall(struct trapframe frame)
+ia32_syscall(struct trapframe *frame)
 {
 	caddr_t params;
 	int i;
@@ -111,18 +111,18 @@ ia32_syscall(struct trapframe frame)
 	PCPU_LAZY_INC(cnt.v_syscall);
 
 	td->td_pticks = 0;
-	td->td_frame = &frame;
+	td->td_frame = frame;
 	if (td->td_ucred != p->p_ucred) 
 		cred_update_thread(td);
-	params = (caddr_t)frame.tf_rsp + sizeof(u_int32_t);
-	code = frame.tf_rax;
-	orig_tf_rflags = frame.tf_rflags;
+	params = (caddr_t)frame->tf_rsp + sizeof(u_int32_t);
+	code = frame->tf_rax;
+	orig_tf_rflags = frame->tf_rflags;
 
 	if (p->p_sysent->sv_prepsyscall) {
 		/*
 		 * The prep code is MP aware.
 		 */
-		(*p->p_sysent->sv_prepsyscall)(&frame, args, &code, &params);
+		(*p->p_sysent->sv_prepsyscall)(frame, args, &code, &params);
 	} else {
 		/*
 		 * Need to check if this is a 32 bit or 64 bit syscall.
@@ -177,7 +177,7 @@ ia32_syscall(struct trapframe frame)
 
 	if (error == 0) {
 		td->td_retval[0] = 0;
-		td->td_retval[1] = frame.tf_rdx;
+		td->td_retval[1] = frame->tf_rdx;
 
 		STOPEVENT(p, S_SCE, narg);
 
@@ -190,9 +190,9 @@ ia32_syscall(struct trapframe frame)
 
 	switch (error) {
 	case 0:
-		frame.tf_rax = td->td_retval[0];
-		frame.tf_rdx = td->td_retval[1];
-		frame.tf_rflags &= ~PSL_C;
+		frame->tf_rax = td->td_retval[0];
+		frame->tf_rdx = td->td_retval[1];
+		frame->tf_rflags &= ~PSL_C;
 		break;
 
 	case ERESTART:
@@ -200,7 +200,7 @@ ia32_syscall(struct trapframe frame)
 		 * Reconstruct pc, assuming lcall $X,y is 7 bytes,
 		 * int 0x80 is 2 bytes. We saved this in tf_err.
 		 */
-		frame.tf_rip -= frame.tf_err;
+		frame->tf_rip -= frame->tf_err;
 		break;
 
 	case EJUSTRETURN:
@@ -213,8 +213,8 @@ ia32_syscall(struct trapframe frame)
    			else
   				error = p->p_sysent->sv_errtbl[error];
 		}
-		frame.tf_rax = error;
-		frame.tf_rflags |= PSL_C;
+		frame->tf_rax = error;
+		frame->tf_rflags |= PSL_C;
 		break;
 	}
 
@@ -222,11 +222,11 @@ ia32_syscall(struct trapframe frame)
 	 * Traced syscall.
 	 */
 	if (orig_tf_rflags & PSL_T) {
-		frame.tf_rflags &= ~PSL_T;
+		frame->tf_rflags &= ~PSL_T;
 		ksiginfo_init_trap(&ksi);
 		ksi.ksi_signo = SIGTRAP;
 		ksi.ksi_code = TRAP_TRACE;
-		ksi.ksi_addr = (void *)frame.tf_rip;
+		ksi.ksi_addr = (void *)frame->tf_rip;
 		trapsignal(td, &ksi);
 	}
 
@@ -246,7 +246,7 @@ ia32_syscall(struct trapframe frame)
 	/*
 	 * Handle reschedule and other end-of-syscall issues
 	 */
-	userret(td, &frame);
+	userret(td, frame);
 
 	CTR4(KTR_SYSC, "syscall exit thread %p pid %d proc %s code %d", td,
 	    td->td_proc->p_pid, td->td_proc->p_comm, code);