From 1544e0f5d1f1e3b8c10a64cb899a936976ca7ea4 Mon Sep 17 00:00:00 2001
From: Brooks Davis <brooks@FreeBSD.org>
Date: Wed, 12 Jan 2022 22:50:06 +0000
Subject: [PATCH] syscallarg_t: Add a type for system call arguments

This more clearly differentiates system call arguments from integer
registers and return values. On current architectures it has no effect,
but on architectures where pointers are not integers (CHERI) and may
not even share registers (CHERI-MIPS) it is necessiary to differentiate
between system call arguments (syscallarg_t) and integer register values
(register_t).

Obtained from:	CheriBSD

Reviewed by:	imp, kib
Differential Revision:	https://reviews.freebsd.org/D33780
---
 sys/amd64/amd64/trap.c     |  2 +-
 sys/arm/arm/syscall.c      |  6 +++---
 sys/arm64/arm64/trap.c     |  4 ++--
 sys/kern/kern_ktrace.c     |  2 +-
 sys/kern/sys_process.c     |  4 ++--
 sys/riscv/riscv/trap.c     |  4 ++--
 sys/sys/ktrace.h           |  2 +-
 sys/sys/proc.h             |  2 +-
 sys/sys/ptrace.h           |  2 +-
 sys/sys/types.h            |  2 ++
 sys/tools/makesyscalls.lua | 10 +++++-----
 sys/vm/vm_mmap.c           |  2 +-
 usr.bin/truss/syscall.h    |  8 ++++----
 usr.bin/truss/syscalls.c   |  4 ++--
 usr.bin/truss/truss.h      |  2 +-
 15 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index ff4bccebed5..bebc8cc117d 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -1011,7 +1011,7 @@ cpu_fetch_syscall_args_fallback(struct thread *td, struct syscall_args *sa)
 {
 	struct proc *p;
 	struct trapframe *frame;
-	register_t *argp;
+	syscallarg_t *argp;
 	caddr_t params;
 	int reg, regcnt, error;
 
diff --git a/sys/arm/arm/syscall.c b/sys/arm/arm/syscall.c
index a635de0ec71..c083bf552eb 100644
--- a/sys/arm/arm/syscall.c
+++ b/sys/arm/arm/syscall.c
@@ -100,7 +100,7 @@ int
 cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
-	register_t *ap;
+	syscallarg_t *ap;
 	struct syscall_args *sa;
 	u_int nap;
 	int error;
@@ -124,10 +124,10 @@ cpu_fetch_syscall_args(struct thread *td)
 	else
 		sa->callp = &p->p_sysent->sv_table[sa->code];
 	error = 0;
-	memcpy(sa->args, ap, nap * sizeof(register_t));
+	memcpy(sa->args, ap, nap * sizeof(*sa->args));
 	if (sa->callp->sy_narg > nap) {
 		error = copyin((void *)td->td_frame->tf_usr_sp, sa->args +
-		    nap, (sa->callp->sy_narg - nap) * sizeof(register_t));
+		    nap, (sa->callp->sy_narg - nap) * sizeof(*sa->args));
 	}
 	if (error == 0) {
 		td->td_retval[0] = 0;
diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index 3e4bc196e19..4aa788bea94 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -134,7 +134,7 @@ int
 cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
-	register_t *ap, *dst_ap;
+	syscallarg_t *ap, *dst_ap;
 	struct syscall_args *sa;
 
 	p = td->td_proc;
@@ -159,7 +159,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	KASSERT(sa->callp->sy_narg <= nitems(sa->args),
 	    ("Syscall %d takes too many arguments", sa->code));
 
-	memcpy(dst_ap, ap, (nitems(sa->args) - 1) * sizeof(register_t));
+	memcpy(dst_ap, ap, (nitems(sa->args) - 1) * sizeof(*dst_ap));
 
 	td->td_retval[0] = 0;
 	td->td_retval[1] = 0;
diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index 5371f73672a..d8db964ada0 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -524,7 +524,7 @@ ktr_get_tracevp(struct proc *p, bool ref)
 }
 
 void
-ktrsyscall(int code, int narg, register_t args[])
+ktrsyscall(int code, int narg, syscallarg_t args[])
 {
 	struct ktr_request *req;
 	struct ktr_syscall *ktp;
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index 2c212edd0ae..a708ed2bde1 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -474,7 +474,7 @@ sys_ptrace(struct thread *td, struct ptrace_args *uap)
 		struct dbreg dbreg;
 		struct fpreg fpreg;
 		struct reg reg;
-		char args[sizeof(td->td_sa.args)];
+		syscallarg_t args[nitems(td->td_sa.args)];
 		struct ptrace_sc_ret psr;
 		int ptevents;
 	} r;
@@ -1010,7 +1010,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		/* See the explanation in linux_ptrace_get_syscall_info(). */
 		bcopy(td2->td_sa.args, addr, SV_PROC_ABI(td->td_proc) ==
 		    SV_ABI_LINUX ? sizeof(td2->td_sa.args) :
-		    td2->td_sa.callp->sy_narg * sizeof(register_t));
+		    td2->td_sa.callp->sy_narg * sizeof(syscallarg_t));
 		break;
 
 	case PT_GET_SC_RET:
diff --git a/sys/riscv/riscv/trap.c b/sys/riscv/riscv/trap.c
index 8eb52fcc533..4bd6d766ec3 100644
--- a/sys/riscv/riscv/trap.c
+++ b/sys/riscv/riscv/trap.c
@@ -94,7 +94,7 @@ int
 cpu_fetch_syscall_args(struct thread *td)
 {
 	struct proc *p;
-	register_t *ap, *dst_ap;
+	syscallarg_t *ap, *dst_ap;
 	struct syscall_args *sa;
 
 	p = td->td_proc;
@@ -119,7 +119,7 @@ cpu_fetch_syscall_args(struct thread *td)
 	KASSERT(sa->callp->sy_narg <= nitems(sa->args),
 	    ("Syscall %d takes too many arguments", sa->code));
 
-	memcpy(dst_ap, ap, (NARGREG - 1) * sizeof(register_t));
+	memcpy(dst_ap, ap, (NARGREG - 1) * sizeof(*dst_ap));
 
 	td->td_retval[0] = 0;
 	td->td_retval[1] = 0;
diff --git a/sys/sys/ktrace.h b/sys/sys/ktrace.h
index 283a95c36d6..d00981a93d2 100644
--- a/sys/sys/ktrace.h
+++ b/sys/sys/ktrace.h
@@ -284,7 +284,7 @@ void	ktrpsig(int, sig_t, sigset_t *, int);
 void	ktrfault(vm_offset_t, int);
 void	ktrfaultend(int);
 void	ktrgenio(int, enum uio_rw, struct uio *, int);
-void	ktrsyscall(int, int narg, register_t args[]);
+void	ktrsyscall(int, int narg, syscallarg_t args[]);
 void	ktrsysctl(int *name, u_int namelen);
 void	ktrsysret(int, int, register_t);
 void	ktrprocctor(struct proc *);
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index ff97bfbd54a..312adc517ae 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -357,7 +357,7 @@ struct thread {
 	} td_state;			/* (t) thread state */
 	/* Note: td_state must be accessed using TD_{GET,SET}_STATE(). */
 	union {
-		register_t	tdu_retval[2];
+		syscallarg_t	tdu_retval[2];
 		off_t		tdu_off;
 	} td_uretoff;			/* (k) Syscall aux returns. */
 #define td_retval	td_uretoff.tdu_retval
diff --git a/sys/sys/ptrace.h b/sys/sys/ptrace.h
index 1e7c1c71056..c4be99c5207 100644
--- a/sys/sys/ptrace.h
+++ b/sys/sys/ptrace.h
@@ -160,7 +160,7 @@ struct ptrace_lwpinfo32 {
 
 /* Argument structure for PT_GET_SC_RET. */
 struct ptrace_sc_ret {
-	register_t	sr_retval[2];	/* Only valid if sr_error == 0. */
+	syscallarg_t	sr_retval[2];	/* Only valid if sr_error == 0. */
 	int		sr_error;
 };
 
diff --git a/sys/sys/types.h b/sys/sys/types.h
index 66f11aa3e31..d37ab8b823d 100644
--- a/sys/sys/types.h
+++ b/sys/sys/types.h
@@ -270,6 +270,8 @@ typedef	__vm_size_t	vm_size_t;
 
 typedef __rman_res_t    rman_res_t;
 
+typedef __register_t	syscallarg_t;
+
 #ifdef _KERNEL
 typedef	int		boolean_t;
 typedef	struct _device	*device_t;
diff --git a/sys/tools/makesyscalls.lua b/sys/tools/makesyscalls.lua
index 178869d03b0..ec79ae30d13 100644
--- a/sys/tools/makesyscalls.lua
+++ b/sys/tools/makesyscalls.lua
@@ -860,7 +860,7 @@ local function handle_noncompat(sysnum, thr_flag, flags, sysflags, rettype,
 			write_line("sysarg", "};\n")
 		else
 			write_line("sysarg", string.format(
-			    "struct %s {\n\tregister_t dummy;\n};\n", argalias))
+			    "struct %s {\n\tsyscallarg_t dummy;\n};\n", argalias))
 		end
 	end
 
@@ -986,7 +986,7 @@ local function handle_compat(sysnum, thr_flag, flags, sysflags, rettype,
 		write_line(out, "};\n")
 	elseif flags & nargflags == 0 then
 		write_line("sysarg", string.format(
-		    "struct %s {\n\tregister_t dummy;\n};\n", argalias))
+		    "struct %s {\n\tsyscallarg_t dummy;\n};\n", argalias))
 	end
 	if flags & dprotoflags == 0 then
 		write_line(outdcl, string.format(
@@ -1439,8 +1439,8 @@ struct proc;
 
 struct thread;
 
-#define	PAD_(t)	(sizeof(register_t) <= sizeof(t) ? \
-		0 : sizeof(register_t) - sizeof(t))
+#define	PAD_(t)	(sizeof(syscallarg_t) <= sizeof(t) ? \
+		0 : sizeof(syscallarg_t) - sizeof(t))
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define	PADL_(t)	0
@@ -1530,7 +1530,7 @@ systrace_return_setargdesc(int sysnum, int ndx, char *desc, size_t descsz)
 process_sysfile(sysfile)
 
 write_line("sysinc",
-    "\n#define AS(name) (sizeof(struct name) / sizeof(register_t))\n")
+    "\n#define AS(name) (sizeof(struct name) / sizeof(syscallarg_t))\n")
 
 for _, v in pairs(compat_options) do
 	if v["count"] > 0 then
diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 8ad049ed6d5..db9a32d1c9b 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -420,7 +420,7 @@ kern_mmap(struct thread *td, const struct mmap_req *mrp)
 	}
 
 	if (error == 0)
-		td->td_retval[0] = (register_t) (addr + pageoff);
+		td->td_retval[0] = addr + pageoff;
 done:
 	if (fp)
 		fdrop(fp, td);
diff --git a/usr.bin/truss/syscall.h b/usr.bin/truss/syscall.h
index 7a403d5b680..ba3a4a50a92 100644
--- a/usr.bin/truss/syscall.h
+++ b/usr.bin/truss/syscall.h
@@ -227,7 +227,7 @@ struct syscall {
 };
 
 struct syscall *get_syscall(struct threadinfo *, u_int, u_int);
-char *print_arg(struct syscall_arg *, unsigned long *, register_t *,
+char *print_arg(struct syscall_arg *, unsigned long *, syscallarg_t *,
     struct trussinfo *);
 
 /*
@@ -251,8 +251,8 @@ char *print_arg(struct syscall_arg *, unsigned long *, register_t *,
 #define LINUX_SENDMSG		16
 #define LINUX_RECVMSG		17
 
-#define PAD_(t) (sizeof(register_t) <= sizeof(t) ? \
-    0 : sizeof(register_t) - sizeof(t))
+#define PAD_(t) (sizeof(syscallarg_t) <= sizeof(t) ? \
+    0 : sizeof(syscallarg_t) - sizeof(t))
 
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define PADL_(t)	0
@@ -271,5 +271,5 @@ struct linux_socketcall_args {
 };
 
 void print_syscall(struct trussinfo *);
-void print_syscall_ret(struct trussinfo *, int, register_t *);
+void print_syscall_ret(struct trussinfo *, int, syscallarg_t *);
 void print_summary(struct trussinfo *trussinfo);
diff --git a/usr.bin/truss/syscalls.c b/usr.bin/truss/syscalls.c
index 586b583c320..e538fa713df 100644
--- a/usr.bin/truss/syscalls.c
+++ b/usr.bin/truss/syscalls.c
@@ -1556,7 +1556,7 @@ user_ptr32_to_psaddr(int32_t user_pointer)
  * an array of all of the system call arguments.
  */
 char *
-print_arg(struct syscall_arg *sc, unsigned long *args, register_t *retval,
+print_arg(struct syscall_arg *sc, unsigned long *args, syscallarg_t *retval,
     struct trussinfo *trussinfo)
 {
 	FILE *fp;
@@ -2729,7 +2729,7 @@ print_syscall(struct trussinfo *trussinfo)
 }
 
 void
-print_syscall_ret(struct trussinfo *trussinfo, int error, register_t *retval)
+print_syscall_ret(struct trussinfo *trussinfo, int error, syscallarg_t *retval)
 {
 	struct timespec timediff;
 	struct threadinfo *t;
diff --git a/usr.bin/truss/truss.h b/usr.bin/truss/truss.h
index a3ce8f27d95..4d2680cd491 100644
--- a/usr.bin/truss/truss.h
+++ b/usr.bin/truss/truss.h
@@ -81,7 +81,7 @@ struct current_syscall {
 	struct syscall *sc;
 	unsigned int number;
 	unsigned int nargs;
-	unsigned long args[10];
+	syscallarg_t args[10];
 	char *s_args[10];	/* the printable arguments */
 };