STACKALIGN: Reimplement in terms of __align_down

This changes STACKALIGN to be type-preserving when operating on
pointers.

Reviewed by:	brooks, kib
Effort:		CHERI upstreaming
Sponsored by:	AFRL, DARPA
Differential Revision:	https://reviews.freebsd.org/D54920

lib/libc/aarch64/gen/makecontext.c

@@ -74,7 +74,8 @@ __makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
 	va_end(ap);
 
 	/* Set the stack */
-	gp->gp_sp = STACKALIGN(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
+	gp->gp_sp = STACKALIGN((uintptr_t)ucp->uc_stack.ss_sp +
+	    ucp->uc_stack.ss_size);
 	/* Arrange for return via the trampoline code. */
 	gp->gp_elr = (__register_t)_ctx_start;
 	gp->gp_x[19] = (__register_t)func;

lib/libc/riscv/gen/makecontext.c

@@ -80,7 +80,8 @@ __makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
 	va_end(ap);
 
 	/* Set the stack */
-	gp->gp_sp = STACKALIGN(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
+	gp->gp_sp = STACKALIGN((uintptr_t)ucp->uc_stack.ss_sp +
+	    ucp->uc_stack.ss_size);
 	/* Arrange for return via the trampoline code. */
 	gp->gp_sepc = (__register_t)_ctx_start;
 	gp->gp_s[0] = (__register_t)func;

sys/arm/arm/exec_machdep.c

@@ -307,7 +307,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	fp--;
 
 	/* make the stack aligned */
-	fp = (struct sigframe *)STACKALIGN(fp);
+	fp = STACKALIGN(fp);
 	/* Populate the siginfo frame. */
 	bzero(&frame, sizeof(frame));
 	get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);

sys/arm/arm/machdep.c

@@ -655,7 +655,7 @@ initarm(struct arm_boot_params *abp)
 	}
 #endif
 
-	return ((void *)STACKALIGN(thread0.td_pcb));
+	return (STACKALIGN(thread0.td_pcb));
 
 }
 #endif /* FDT */

sys/arm/arm/vm_machdep.c

@@ -129,7 +129,7 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
 	pcb2->pcb_regs.sf_r4 = (register_t)fork_return;
 	pcb2->pcb_regs.sf_r5 = (register_t)td2;
 	pcb2->pcb_regs.sf_lr = (register_t)fork_trampoline;
-	pcb2->pcb_regs.sf_sp = STACKALIGN(td2->td_frame);
+	pcb2->pcb_regs.sf_sp = (register_t)STACKALIGN(td2->td_frame);
 	pcb2->pcb_regs.sf_tpidrurw = (register_t)get_tls();
 
 #ifdef VFP
@@ -194,7 +194,7 @@ cpu_copy_thread(struct thread *td, struct thread *td0)
 	td->td_pcb->pcb_regs.sf_r4 = (register_t)fork_return;
 	td->td_pcb->pcb_regs.sf_r5 = (register_t)td;
 	td->td_pcb->pcb_regs.sf_lr = (register_t)fork_trampoline;
-	td->td_pcb->pcb_regs.sf_sp = STACKALIGN(td->td_frame);
+	td->td_pcb->pcb_regs.sf_sp = (register_t)STACKALIGN(td->td_frame);
 
 	td->td_frame->tf_spsr &= ~PSR_C;
 	td->td_frame->tf_r0 = 0;

sys/arm/include/param.h

@@ -47,7 +47,6 @@
 #include <sys/_align.h>
 
 #define STACKALIGNBYTES	(8 - 1)
-#define STACKALIGN(p)	((u_int)(p) & ~STACKALIGNBYTES)
 
 #ifndef MACHINE
 #define	MACHINE		"arm"

sys/arm64/arm64/exec_machdep.c

@@ -838,7 +838,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	/* Make room, keeping the stack aligned */
 	fp = (struct sigframe *)addr;
 	fp--;
-	fp = (struct sigframe *)STACKALIGN(fp);
+	fp = STACKALIGN(fp);
 
 	/* Copy the sigframe out to the user's stack. */
 	if (copyout(&frame, fp, sizeof(*fp)) != 0) {

sys/arm64/arm64/vm_machdep.c

@@ -100,7 +100,7 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
 
 	ptrauth_fork(td2, td1);
 
-	tf = (struct trapframe *)STACKALIGN((struct trapframe *)pcb2 - 1);
+	tf = STACKALIGN((struct trapframe *)pcb2 - 1);
 	bcopy(td1->td_frame, tf, sizeof(*tf));
 	tf->tf_x[0] = 0;
 	tf->tf_x[1] = 0;

sys/arm64/include/param.h

@@ -41,7 +41,6 @@
 #include <sys/_align.h>
 
 #define	STACKALIGNBYTES	(16 - 1)
-#define	STACKALIGN(p)	((uint64_t)(p) & ~STACKALIGNBYTES)
 
 #ifndef MACHINE
 #define	MACHINE		"arm64"

sys/arm64/linux/linux_sysvec.c

@@ -338,7 +338,7 @@ linux_rt_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 
 	/* Make room, keeping the stack aligned */
 	fp--;
-	fp = (struct l_sigframe *)STACKALIGN(fp);
+	fp = STACKALIGN(fp);
 
 	get_mcontext(td, &uc.uc_mcontext, 0);
 	uc.uc_sigmask = *mask;

sys/riscv/include/param.h

@@ -37,7 +37,6 @@
 #include <sys/_align.h>
 
 #define	STACKALIGNBYTES	(16 - 1)
-#define	STACKALIGN(p)	((uint64_t)(p) & ~STACKALIGNBYTES)
 
 #ifndef MACHINE
 #define	MACHINE		"riscv"

sys/riscv/riscv/exec_machdep.c

@@ -370,7 +370,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 
 	/* Make room, keeping the stack aligned */
 	fp--;
-	fp = (struct sigframe *)STACKALIGN(fp);
+	fp = STACKALIGN(fp);
 
 	/* Fill in the frame to copy out */
 	bzero(&frame, sizeof(frame));

sys/sys/param.h

@@ -179,6 +179,9 @@
 #ifndef MAXDUMPPGS
 #define MAXDUMPPGS	(DFLTPHYS/PAGE_SIZE)
 #endif
+#ifdef STACKALIGNBYTES
+#define	STACKALIGN(p)	(__align_down(p, STACKALIGNBYTES + 1))
+#endif
 
 /*
  * Constants related to network buffer management.