[RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Steven Rostedt]

Two and a half years ago I sent out 3 patches and a title letter that
had this[1]:

  At Linux Plumbers, Andy Lutomirski approached me to tell me that the
  syscall_get_arguments() implementation in x86 was horrible and gcc
  certainly gets it wrong. He said that since the tracepoints only pass
  in 0 and 6 for i and n repectively, it should be optimized for that case.
  Inspecting the kernel, I discovered that all users pass in 0 for i and
  only one file passing in something other than 6 for the number of arguments.
  That code happens to be my own code used for the special syscall tracing.
  That can easily be converted to just using 0 and 6 as well, and only copying
  what is needed. Which is probably the faster path anyway for that case.

  I haven't run the numbers (I can do that when I get some time), but since
  pretty much all use cases use 0 and 6 and that would allow these functions
  not to need strange logic to handle odd cases, I think this is still a win.

It received positive comments but also Linus asked to remove the separate
arg pointers and replace them with a single structure and fill that
instead. But for some reason, this got pushed aside and forgotten (probably,
had to do with the fact that I left Red Hat shortly after this).

Recently, it was brought back up again[2] and I decided to dust off these
patches and resubmit them. I also added one more patch to do the same
for syscall_set_arguments() that I did for syscall_get_arguments() even
though syscall_set_arguments() currently (and never has) had any callers.
But we are told that in the near future it may have one.

The changes do optimize the logic a little, but for most archs I just kept
the same logic (loops and such) as I don't have a way to test it, and
didn't want to break the logic.

I added a new struct syscall_info that holds seccomp_data and also
includes a stack pointer (sp) field. I would change seccomp_data,
but because its in include/uapi/linux/seccomp.h I didn't want to
touch it and break userspace. Perhaps we could add the field at the
end, but I didn't want to chance it (unless others say its OK).

I ran these through zero-day-bot and compiled tested these changes for
all architectures except for csky which I do not have a cross compiler
for.

Note the following archs fail normal builds, but they fail the same
with these patches:

   arc
   h8300
   parisc64

Note, you may notice that I have "(Red Hat)" as the author of the
first three patches (even though they are signed off by "(VMware)").
This is because those patches were originally written while I was
working for Red Hat. But as I forward ported them while working for
VMware, my signed-off-by reflects that.

[1] - https://lore.kernel.org/lkml/20161107212634.529267342@goodmis.org/T/#u
[2] - https://lore.kernel.org/lkml/20190326151244.GC16837@redhat.com/T/#u

Steven Rostedt (Red Hat) (3):
      ptrace: Remove maxargs from task_current_syscall()
      tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()
      syscalls: Remove start and number from syscall_get_arguments() args

Steven Rostedt (VMware) (1):
      syscalls: Remove start and number from syscall_set_arguments() args

----
 arch/arc/include/asm/syscall.h        |   7 +-
 arch/arm/include/asm/syscall.h        |  47 ++---------
 arch/arm64/include/asm/syscall.h      |  46 ++---------
 arch/c6x/include/asm/syscall.h        |  79 ++++---------------
 arch/csky/include/asm/syscall.h       |  26 ++-----
 arch/h8300/include/asm/syscall.h      |  34 ++------
 arch/hexagon/include/asm/syscall.h    |   4 +-
 arch/ia64/include/asm/syscall.h       |  13 +---
 arch/ia64/kernel/ptrace.c             |   7 +-
 arch/microblaze/include/asm/syscall.h |   8 +-
 arch/mips/include/asm/syscall.h       |   3 +-
 arch/mips/kernel/ptrace.c             |   2 +-
 arch/nds32/include/asm/syscall.h      |  62 +++------------
 arch/nios2/include/asm/syscall.h      |  84 ++++----------------
 arch/openrisc/include/asm/syscall.h   |  12 +--
 arch/parisc/include/asm/syscall.h     |  30 ++-----
 arch/powerpc/include/asm/syscall.h    |  15 ++--
 arch/riscv/include/asm/syscall.h      |  24 ++----
 arch/s390/include/asm/syscall.h       |  28 +++----
 arch/sh/include/asm/syscall_32.h      |  47 +++--------
 arch/sh/include/asm/syscall_64.h      |   8 +-
 arch/sparc/include/asm/syscall.h      |  11 ++-
 arch/um/include/asm/syscall-generic.h |  78 +++----------------
 arch/x86/include/asm/syscall.h        | 142 ++++++++--------------------------
 arch/xtensa/include/asm/syscall.h     |  33 ++------
 fs/proc/base.c                        |  17 ++--
 include/asm-generic/syscall.h         |  21 ++---
 include/linux/ptrace.h                |  11 ++-
 include/trace/events/syscalls.h       |   2 +-
 kernel/seccomp.c                      |   2 +-
 kernel/trace/trace_syscalls.c         |   9 ++-
 lib/syscall.c                         |  57 ++++++--------
 32 files changed, 247 insertions(+), 722 deletions(-)

[RFC][PATCH 1/4 v2] ptrace: Remove maxargs from task_current_syscall()

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

task_current_syscall() has a single user that passes in 6 for maxargs, which
is the maximum arguments that can be used to get system calls from
syscall_get_arguments(). Instead of passing in a number of arguments to
grab, just get 6 arguments. The args argument even specifies that it's an
array of 6 items.

This will also allow changing syscall_get_arguments() to not get a variable
number of arguments, but always grab 6.

Linus also suggested not passing in a bunch of arguments to
task_current_syscall() but to instead pass in a pointer to a structure, and
just fill the structure. struct seccomp_data has almost all the parameters
that is needed except for the stack pointer (sp). As seccomp_data is part of
uapi, and I'm afraid to change it, a new structure was created
"syscall_info", which includes seccomp_data and adds the "sp" field.

Link: http://lkml.kernel.org/r/20161107213233.466776454@goodmis.org

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 fs/proc/base.c         | 17 +++++++------
 include/linux/ptrace.h | 11 +++++---
 lib/syscall.c          | 57 ++++++++++++++++++------------------------
 3 files changed, 42 insertions(+), 43 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ddef482f1334..6a803a0b75df 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -616,24 +616,25 @@ static int proc_pid_limits(struct seq_file *m, struct pid_namespace *ns,
 static int proc_pid_syscall(struct seq_file *m, struct pid_namespace *ns,
 			    struct pid *pid, struct task_struct *task)
 {
-	long nr;
-	unsigned long args[6], sp, pc;
+	struct syscall_info info;
+	u64 *args = &info.data.args[0];
 	int res;
 
 	res = lock_trace(task);
 	if (res)
 		return res;
 
-	if (task_current_syscall(task, &nr, args, 6, &sp, &pc))
+	if (task_current_syscall(task, &info))
 		seq_puts(m, "running\n");
-	else if (nr < 0)
-		seq_printf(m, "%ld 0x%lx 0x%lx\n", nr, sp, pc);
+	else if (info.data.nr < 0)
+		seq_printf(m, "%d 0x%llx 0x%llx\n",
+			   info.data.nr, info.sp, info.data.instruction_pointer);
 	else
 		seq_printf(m,
-		       "%ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
-		       nr,
+		       "%d 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx\n",
+		       info.data.nr,
 		       args[0], args[1], args[2], args[3], args[4], args[5],
-		       sp, pc);
+		       info.sp, info.data.instruction_pointer);
 	unlock_trace(task);
 
 	return 0;
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index edb9b040c94c..d5084ebd9f03 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -9,6 +9,13 @@
 #include <linux/bug.h>			/* For BUG_ON.  */
 #include <linux/pid_namespace.h>	/* For task_active_pid_ns.  */
 #include <uapi/linux/ptrace.h>
+#include <linux/seccomp.h>
+
+/* Add sp to seccomp_data, as seccomp is user API, we don't want to modify it */
+struct syscall_info {
+	__u64			sp;
+	struct seccomp_data	data;
+};
 
 extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
 			    void *buf, int len, unsigned int gup_flags);
@@ -407,9 +414,7 @@ static inline void user_single_step_report(struct pt_regs *regs)
 #define current_user_stack_pointer() user_stack_pointer(current_pt_regs())
 #endif
 
-extern int task_current_syscall(struct task_struct *target, long *callno,
-				unsigned long args[6], unsigned int maxargs,
-				unsigned long *sp, unsigned long *pc);
+extern int task_current_syscall(struct task_struct *target, struct syscall_info *info);
 
 extern void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact);
 #endif
diff --git a/lib/syscall.c b/lib/syscall.c
index 1a7077f20eae..e8467e17b9a2 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -5,16 +5,14 @@
 #include <linux/export.h>
 #include <asm/syscall.h>
 
-static int collect_syscall(struct task_struct *target, long *callno,
-			   unsigned long args[6], unsigned int maxargs,
-			   unsigned long *sp, unsigned long *pc)
+static int collect_syscall(struct task_struct *target, struct syscall_info *info)
 {
 	struct pt_regs *regs;
 
 	if (!try_get_task_stack(target)) {
 		/* Task has no stack, so the task isn't in a syscall. */
-		*sp = *pc = 0;
-		*callno = -1;
+		memset(info, 0, sizeof(*info));
+		info->data.nr = -1;
 		return 0;
 	}
 
@@ -24,12 +22,13 @@ static int collect_syscall(struct task_struct *target, long *callno,
 		return -EAGAIN;
 	}
 
-	*sp = user_stack_pointer(regs);
-	*pc = instruction_pointer(regs);
+	info->sp = user_stack_pointer(regs);
+	info->data.instruction_pointer = instruction_pointer(regs);
 
-	*callno = syscall_get_nr(target, regs);
-	if (*callno != -1L && maxargs > 0)
-		syscall_get_arguments(target, regs, 0, maxargs, args);
+	info->data.nr = syscall_get_nr(target, regs);
+	if (info->data.nr != -1L)
+		syscall_get_arguments(target, regs, 0, 6,
+				      (unsigned long *)&info->data.args[0]);
 
 	put_task_stack(target);
 	return 0;
@@ -38,41 +37,35 @@ static int collect_syscall(struct task_struct *target, long *callno,
 /**
  * task_current_syscall - Discover what a blocked task is doing.
  * @target:		thread to examine
- * @callno:		filled with system call number or -1
- * @args:		filled with @maxargs system call arguments
- * @maxargs:		number of elements in @args to fill
- * @sp:			filled with user stack pointer
- * @pc:			filled with user PC
+ * @info:		structure with the following fields:
+ *			 .sp        - filled with user stack pointer
+ *			 .data.nr   - filled with system call number or -1
+ *			 .data.args - filled with @maxargs system call arguments
+ *			 .data.instruction_pointer - filled with user PC
  *
- * If @target is blocked in a system call, returns zero with *@callno
- * set to the the call's number and @args filled in with its arguments.
- * Registers not used for system call arguments may not be available and
- * it is not kosher to use &struct user_regset calls while the system
+ * If @target is blocked in a system call, returns zero with @info.data.nr
+ * set to the the call's number and @info.data.args filled in with its
+ * arguments. Registers not used for system call arguments may not be available
+ * and it is not kosher to use &struct user_regset calls while the system
  * call is still in progress.  Note we may get this result if @target
  * has finished its system call but not yet returned to user mode, such
  * as when it's stopped for signal handling or syscall exit tracing.
  *
  * If @target is blocked in the kernel during a fault or exception,
- * returns zero with *@callno set to -1 and does not fill in @args.
- * If so, it's now safe to examine @target using &struct user_regset
- * get() calls as long as we're sure @target won't return to user mode.
+ * returns zero with *@info.data.nr set to -1 and does not fill in
+ * @info.data.args. If so, it's now safe to examine @target using
+ * &struct user_regset get() calls as long as we're sure @target won't return
+ * to user mode.
  *
  * Returns -%EAGAIN if @target does not remain blocked.
- *
- * Returns -%EINVAL if @maxargs is too large (maximum is six).
  */
-int task_current_syscall(struct task_struct *target, long *callno,
-			 unsigned long args[6], unsigned int maxargs,
-			 unsigned long *sp, unsigned long *pc)
+int task_current_syscall(struct task_struct *target, struct syscall_info *info)
 {
 	long state;
 	unsigned long ncsw;
 
-	if (unlikely(maxargs > 6))
-		return -EINVAL;
-
 	if (target == current)
-		return collect_syscall(target, callno, args, maxargs, sp, pc);
+		return collect_syscall(target, info);
 
 	state = target->state;
 	if (unlikely(!state))
@@ -80,7 +73,7 @@ int task_current_syscall(struct task_struct *target, long *callno,
 
 	ncsw = wait_task_inactive(target, state);
 	if (unlikely(!ncsw) ||
-	    unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
+	    unlikely(collect_syscall(target, info)) ||
 	    unlikely(wait_task_inactive(target, state) != ncsw))
 		return -EAGAIN;
 
-- 
2.20.1

[RFC][PATCH 2/4 v2] tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The only users that calls syscall_get_arguments() with a variable and not a
hard coded '6' is ftrace_syscall_enter(). syscall_get_arguments() can be
optimized by removing a variable input, and always grabbing 6 arguments
regardless of what the system call actually uses.

Change ftrace_syscall_enter() to pass the 6 args into a local stack array
and copy the necessary arguments into the trace event as needed.

This is needed to remove two parameters from syscall_get_arguments().

Link: http://lkml.kernel.org/r/20161107213233.627583542@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_syscalls.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index f93a56d2db27..e9f5bbbad6d9 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -314,6 +314,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 	struct ring_buffer_event *event;
 	struct ring_buffer *buffer;
 	unsigned long irq_flags;
+	unsigned long args[6];
 	int pc;
 	int syscall_nr;
 	int size;
@@ -347,7 +348,8 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 
 	entry = ring_buffer_event_data(event);
 	entry->nr = syscall_nr;
-	syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
+	syscall_get_arguments(current, regs, 0, 6, args);
+	memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
 	event_trigger_unlock_commit(trace_file, buffer, event, entry,
 				    irq_flags, pc);
@@ -583,6 +585,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 	struct syscall_metadata *sys_data;
 	struct syscall_trace_enter *rec;
 	struct hlist_head *head;
+	unsigned long args[6];
 	bool valid_prog_array;
 	int syscall_nr;
 	int rctx;
@@ -613,8 +616,8 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 		return;
 
 	rec->nr = syscall_nr;
-	syscall_get_arguments(current, regs, 0, sys_data->nb_args,
-			       (unsigned long *)&rec->args);
+	syscall_get_arguments(current, regs, 0, 6, args);
+	memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
 	if ((valid_prog_array &&
 	     !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
-- 
2.20.1

[RFC][PATCH 3/4 v2] syscalls: Remove start and number from syscall_get_arguments() args

[Steven Rostedt]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

At Linux Plumbers, Andy Lutomirski approached me and pointed out that the
function call syscall_get_arguments() implemented in x86 was horribly
written and not optimized for the standard case of passing in 0 and 6 for
the starting index and the number of system calls to get. When looking at
all the users of this function, I discovered that all instances pass in only
0 and 6 for these arguments. Instead of having this function handle
different cases that are never used, simply rewrite it to return the first 6
arguments of a system call.

This should help out the performance of tracing system calls by ptrace,
ftrace and perf.

Link: http://lkml.kernel.org/r/20161107213233.754809394@goodmis.org

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Dave Martin <dave.martin@arm.com>
Cc: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-hexagon@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecores.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 arch/arc/include/asm/syscall.h        |  7 ++-
 arch/arm/include/asm/syscall.h        | 23 ++-------
 arch/arm64/include/asm/syscall.h      | 22 ++------
 arch/c6x/include/asm/syscall.h        | 41 +++------------
 arch/csky/include/asm/syscall.h       | 13 ++---
 arch/h8300/include/asm/syscall.h      | 34 +++----------
 arch/hexagon/include/asm/syscall.h    |  4 +-
 arch/ia64/include/asm/syscall.h       |  5 +-
 arch/microblaze/include/asm/syscall.h |  4 +-
 arch/mips/include/asm/syscall.h       |  3 +-
 arch/mips/kernel/ptrace.c             |  2 +-
 arch/nds32/include/asm/syscall.h      | 33 +++---------
 arch/nios2/include/asm/syscall.h      | 42 +++------------
 arch/openrisc/include/asm/syscall.h   |  6 +--
 arch/parisc/include/asm/syscall.h     | 30 +++--------
 arch/powerpc/include/asm/syscall.h    |  8 ++-
 arch/riscv/include/asm/syscall.h      | 12 ++---
 arch/s390/include/asm/syscall.h       | 17 ++-----
 arch/sh/include/asm/syscall_32.h      | 26 +++-------
 arch/sh/include/asm/syscall_64.h      |  4 +-
 arch/sparc/include/asm/syscall.h      |  4 +-
 arch/um/include/asm/syscall-generic.h | 39 +++-----------
 arch/x86/include/asm/syscall.h        | 73 +++++++--------------------
 arch/xtensa/include/asm/syscall.h     | 16 ++----
 include/asm-generic/syscall.h         | 11 ++--
 include/trace/events/syscalls.h       |  2 +-
 kernel/seccomp.c                      |  2 +-
 kernel/trace/trace_syscalls.c         |  4 +-
 lib/syscall.c                         |  2 +-
 29 files changed, 113 insertions(+), 376 deletions(-)

diff --git a/arch/arc/include/asm/syscall.h b/arch/arc/include/asm/syscall.h
index 29de09804306..c7a4201ed62b 100644
--- a/arch/arc/include/asm/syscall.h
+++ b/arch/arc/include/asm/syscall.h
@@ -55,12 +55,11 @@ syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  */
 static inline void
 syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, unsigned long *args)
+		      unsigned long *args)
 {
 	unsigned long *inside_ptregs = &(regs->r0);
-	inside_ptregs -= i;
-
-	BUG_ON((i + n) > 6);
+	unsigned int n = 6;
+	unsigned int i = 0;
 
 	while (n--) {
 		args[i++] = (*inside_ptregs);
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index 06dea6bce293..db969a2972ae 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -55,29 +55,12 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	if (n == 0)
-		return;
-
-	if (i + n > SYSCALL_MAX_ARGS) {
-		unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i;
-		unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
-		pr_warn("%s called with max args %d, handling only %d\n",
-			__func__, i + n, SYSCALL_MAX_ARGS);
-		memset(args_bad, 0, n_bad * sizeof(args[0]));
-		n = SYSCALL_MAX_ARGS - i;
-	}
-
-	if (i == 0) {
-		args[0] = regs->ARM_ORIG_r0;
-		args++;
-		i++;
-		n--;
-	}
+	args[0] = regs->ARM_ORIG_r0;
+	args++;
 
-	memcpy(args, &regs->ARM_r0 + i, n * sizeof(args[0]));
+	memcpy(args, &regs->ARM_r0 + 1, 5 * sizeof(args[0]));
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index ad8be16a39c9..55b2dab21023 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -65,28 +65,12 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	if (n == 0)
-		return;
-
-	if (i + n > SYSCALL_MAX_ARGS) {
-		unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i;
-		unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
-		pr_warning("%s called with max args %d, handling only %d\n",
-			   __func__, i + n, SYSCALL_MAX_ARGS);
-		memset(args_bad, 0, n_bad * sizeof(args[0]));
-	}
-
-	if (i == 0) {
-		args[0] = regs->orig_x0;
-		args++;
-		i++;
-		n--;
-	}
+	args[0] = regs->orig_x0;
+	args++;
 
-	memcpy(args, &regs->regs[i], n * sizeof(args[0]));
+	memcpy(args, &regs->regs[1], 5 * sizeof(args[0]));
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/c6x/include/asm/syscall.h b/arch/c6x/include/asm/syscall.h
index ae2be315ee9c..06db3251926b 100644
--- a/arch/c6x/include/asm/syscall.h
+++ b/arch/c6x/include/asm/syscall.h
@@ -46,40 +46,15 @@ static inline void syscall_set_return_value(struct task_struct *task,
 }
 
 static inline void syscall_get_arguments(struct task_struct *task,
-					 struct pt_regs *regs, unsigned int i,
-					 unsigned int n, unsigned long *args)
+					 struct pt_regs *regs,
+					 unsigned long *args)
 {
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		*args++ = regs->a4;
-	case 1:
-		if (!n--)
-			break;
-		*args++ = regs->b4;
-	case 2:
-		if (!n--)
-			break;
-		*args++ = regs->a6;
-	case 3:
-		if (!n--)
-			break;
-		*args++ = regs->b6;
-	case 4:
-		if (!n--)
-			break;
-		*args++ = regs->a8;
-	case 5:
-		if (!n--)
-			break;
-		*args++ = regs->b8;
-	case 6:
-		if (!n--)
-			break;
-	default:
-		BUG();
-	}
+	*args++ = regs->a4;
+	*args++ = regs->b4;
+	*args++ = regs->a6;
+	*args++ = regs->b6;
+	*args++ = regs->a8;
+	*args   = regs->b8;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/csky/include/asm/syscall.h b/arch/csky/include/asm/syscall.h
index d637445737b7..5cc0b8283a69 100644
--- a/arch/csky/include/asm/syscall.h
+++ b/arch/csky/include/asm/syscall.h
@@ -43,16 +43,11 @@ syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
 
 static inline void
 syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, unsigned long *args)
+		      unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	if (i == 0) {
-		args[0] = regs->orig_a0;
-		args++;
-		i++;
-		n--;
-	}
-	memcpy(args, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
+	args[0] = regs->orig_a0;
+	args++;
+	memcpy(args, &regs->a1 + sizeof(regs->a1), 5 * sizeof(args[0]));
 }
 
 static inline void
diff --git a/arch/h8300/include/asm/syscall.h b/arch/h8300/include/asm/syscall.h
index 924990401237..ddd483c6ca95 100644
--- a/arch/h8300/include/asm/syscall.h
+++ b/arch/h8300/include/asm/syscall.h
@@ -17,34 +17,14 @@ syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 
 static inline void
 syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, unsigned long *args)
+		      unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	while (n > 0) {
-		switch (i) {
-		case 0:
-			*args++ = regs->er1;
-			break;
-		case 1:
-			*args++ = regs->er2;
-			break;
-		case 2:
-			*args++ = regs->er3;
-			break;
-		case 3:
-			*args++ = regs->er4;
-			break;
-		case 4:
-			*args++ = regs->er5;
-			break;
-		case 5:
-			*args++ = regs->er6;
-			break;
-		}
-		i++;
-		n--;
-	}
+	*args++ = regs->er1;
+	*args++ = regs->er2;
+	*args++ = regs->er3;
+	*args++ = regs->er4;
+	*args++ = regs->er5;
+	*args   = regs->er6;
 }
 
 
diff --git a/arch/hexagon/include/asm/syscall.h b/arch/hexagon/include/asm/syscall.h
index 4af9c7b6f13a..ae3a1e24fabd 100644
--- a/arch/hexagon/include/asm/syscall.h
+++ b/arch/hexagon/include/asm/syscall.h
@@ -37,10 +37,8 @@ static inline long syscall_get_nr(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	memcpy(args, &(&regs->r00)[i], n * sizeof(args[0]));
+	memcpy(args, &(&regs->r00)[0], 6 * sizeof(args[0]));
 }
 #endif
diff --git a/arch/ia64/include/asm/syscall.h b/arch/ia64/include/asm/syscall.h
index 1d0b875fec44..8204c1ff70ce 100644
--- a/arch/ia64/include/asm/syscall.h
+++ b/arch/ia64/include/asm/syscall.h
@@ -63,12 +63,9 @@ extern void ia64_syscall_get_set_arguments(struct task_struct *task,
 	unsigned long *args, int rw);
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	ia64_syscall_get_set_arguments(task, regs, i, n, args, 0);
+	ia64_syscall_get_set_arguments(task, regs, 0, 6, args, 0);
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/microblaze/include/asm/syscall.h b/arch/microblaze/include/asm/syscall.h
index 220decd605a4..4b23e44e5c3c 100644
--- a/arch/microblaze/include/asm/syscall.h
+++ b/arch/microblaze/include/asm/syscall.h
@@ -82,9 +82,11 @@ static inline void microblaze_set_syscall_arg(struct pt_regs *regs,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
+	unsigned int i = 0;
+	unsigned int n = 6;
+
 	while (n--)
 		*args++ = microblaze_get_syscall_arg(regs, i++);
 }
diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
index 6cf8ffb5367e..a2b4748655df 100644
--- a/arch/mips/include/asm/syscall.h
+++ b/arch/mips/include/asm/syscall.h
@@ -116,9 +116,10 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
+	unsigned int i = 0;
+	unsigned int n = 6;
 	int ret;
 
 	/* O32 ABI syscall() */
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 0057c910bc2f..3a62f80958e1 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -1419,7 +1419,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
 
 		sd.nr = syscall;
 		sd.arch = syscall_get_arch();
-		syscall_get_arguments(current, regs, 0, 6, args);
+		syscall_get_arguments(current, regs, args);
 		for (i = 0; i < 6; i++)
 			sd.args[i] = args[i];
 		sd.instruction_pointer = KSTK_EIP(current);
diff --git a/arch/nds32/include/asm/syscall.h b/arch/nds32/include/asm/syscall.h
index f7e5e86765fe..89a6ec8731d8 100644
--- a/arch/nds32/include/asm/syscall.h
+++ b/arch/nds32/include/asm/syscall.h
@@ -108,42 +108,21 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  * syscall_get_arguments - extract system call parameter values
  * @task:	task of interest, must be blocked
  * @regs:	task_pt_regs() of @task
- * @i:		argument index [0,5]
- * @n:		number of arguments; n+i must be [1,6].
  * @args:	array filled with argument values
  *
- * Fetches @n arguments to the system call starting with the @i'th argument
- * (from 0 through 5).  Argument @i is stored in @args[0], and so on.
- * An arch inline version is probably optimal when @i and @n are constants.
+ * Fetches 6 arguments to the system call (from 0 through 5). The first
+ * argument is stored in @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
- * It's invalid to call this with @i + @n > 6; we only support system calls
- * taking up to 6 arguments.
  */
 #define SYSCALL_MAX_ARGS 6
 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-			   unsigned int i, unsigned int n, unsigned long *args)
+			   unsigned long *args)
 {
-	if (n == 0)
-		return;
-	if (i + n > SYSCALL_MAX_ARGS) {
-		unsigned long *args_bad = args + SYSCALL_MAX_ARGS - i;
-		unsigned int n_bad = n + i - SYSCALL_MAX_ARGS;
-		pr_warning("%s called with max args %d, handling only %d\n",
-			   __func__, i + n, SYSCALL_MAX_ARGS);
-		memset(args_bad, 0, n_bad * sizeof(args[0]));
-		memset(args_bad, 0, n_bad * sizeof(args[0]));
-	}
-
-	if (i == 0) {
-		args[0] = regs->orig_r0;
-		args++;
-		i++;
-		n--;
-	}
-
-	memcpy(args, &regs->uregs[0] + i, n * sizeof(args[0]));
+	args[0] = regs->orig_r0;
+	args++;
+	memcpy(args, &regs->uregs[0] + 1, 5 * sizeof(args[0]));
 }
 
 /**
diff --git a/arch/nios2/include/asm/syscall.h b/arch/nios2/include/asm/syscall.h
index 9de220854c4a..792bd449d839 100644
--- a/arch/nios2/include/asm/syscall.h
+++ b/arch/nios2/include/asm/syscall.h
@@ -58,42 +58,14 @@ static inline void syscall_set_return_value(struct task_struct *task,
 }
 
 static inline void syscall_get_arguments(struct task_struct *task,
-	struct pt_regs *regs, unsigned int i, unsigned int n,
-	unsigned long *args)
+	struct pt_regs *regs, unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		*args++ = regs->r4;
-	case 1:
-		if (!n--)
-			break;
-		*args++ = regs->r5;
-	case 2:
-		if (!n--)
-			break;
-		*args++ = regs->r6;
-	case 3:
-		if (!n--)
-			break;
-		*args++ = regs->r7;
-	case 4:
-		if (!n--)
-			break;
-		*args++ = regs->r8;
-	case 5:
-		if (!n--)
-			break;
-		*args++ = regs->r9;
-	case 6:
-		if (!n--)
-			break;
-	default:
-		BUG();
-	}
+	*args++ = regs->r4;
+	*args++ = regs->r5;
+	*args++ = regs->r6;
+	*args++ = regs->r7;
+	*args++ = regs->r8;
+	*args   = regs->r9;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/openrisc/include/asm/syscall.h b/arch/openrisc/include/asm/syscall.h
index 2db9f1cf0694..72607860cd55 100644
--- a/arch/openrisc/include/asm/syscall.h
+++ b/arch/openrisc/include/asm/syscall.h
@@ -56,11 +56,9 @@ syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
 
 static inline void
 syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, unsigned long *args)
+		      unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	memcpy(args, &regs->gpr[3 + i], n * sizeof(args[0]));
+	memcpy(args, &regs->gpr[3], 6 * sizeof(args[0]));
 }
 
 static inline void
diff --git a/arch/parisc/include/asm/syscall.h b/arch/parisc/include/asm/syscall.h
index 8bff1a58c97f..62a6d477fae0 100644
--- a/arch/parisc/include/asm/syscall.h
+++ b/arch/parisc/include/asm/syscall.h
@@ -18,29 +18,15 @@ static inline long syscall_get_nr(struct task_struct *tsk,
 }
 
 static inline void syscall_get_arguments(struct task_struct *tsk,
-					 struct pt_regs *regs, unsigned int i,
-					 unsigned int n, unsigned long *args)
+					 struct pt_regs *regs,
+					 unsigned long *args)
 {
-	BUG_ON(i);
-
-	switch (n) {
-	case 6:
-		args[5] = regs->gr[21];
-	case 5:
-		args[4] = regs->gr[22];
-	case 4:
-		args[3] = regs->gr[23];
-	case 3:
-		args[2] = regs->gr[24];
-	case 2:
-		args[1] = regs->gr[25];
-	case 1:
-		args[0] = regs->gr[26];
-	case 0:
-		break;
-	default:
-		BUG();
-	}
+	args[5] = regs->gr[21];
+	args[4] = regs->gr[22];
+	args[3] = regs->gr[23];
+	args[2] = regs->gr[24];
+	args[1] = regs->gr[25];
+	args[0] = regs->gr[26];
 }
 
 static inline long syscall_get_return_value(struct task_struct *task,
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 1a0e7a8b1c81..5c9b9dc82b7e 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -65,22 +65,20 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 	unsigned long val, mask = -1UL;
-
-	BUG_ON(i + n > 6);
+	unsigned int n = 6;
 
 #ifdef CONFIG_COMPAT
 	if (test_tsk_thread_flag(task, TIF_32BIT))
 		mask = 0xffffffff;
 #endif
 	while (n--) {
-		if (n == 0 && i == 0)
+		if (n == 0)
 			val = regs->orig_gpr3;
 		else
-			val = regs->gpr[3 + i + n];
+			val = regs->gpr[3 + n];
 
 		args[n] = val & mask;
 	}
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index bba3da6ef157..85a31dd0f2ba 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -72,17 +72,11 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	if (i == 0) {
-		args[0] = regs->orig_a0;
-		args++;
-		i++;
-		n--;
-	}
-	memcpy(args, &regs->a1 + i * sizeof(regs->a1), n * sizeof(args[0]));
+	args[0] = regs->orig_a0;
+	args++;
+	memcpy(args, &regs->a1 + sizeof(regs->a1), 5 * sizeof(args[0]));
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index 96f9a9151fde..ee0b1f6aa36d 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -56,27 +56,20 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 	unsigned long mask = -1UL;
+	unsigned int n = 6;
 
-	/*
-	 * No arguments for this syscall, there's nothing to do.
-	 */
-	if (!n)
-		return;
-
-	BUG_ON(i + n > 6);
 #ifdef CONFIG_COMPAT
 	if (test_tsk_thread_flag(task, TIF_31BIT))
 		mask = 0xffffffff;
 #endif
 	while (n-- > 0)
-		if (i + n > 0)
-			args[n] = regs->gprs[2 + i + n] & mask;
-	if (i == 0)
-		args[0] = regs->orig_gpr2 & mask;
+		if (n > 0)
+			args[n] = regs->gprs[2 + n] & mask;
+
+	args[0] = regs->orig_gpr2 & mask;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/sh/include/asm/syscall_32.h b/arch/sh/include/asm/syscall_32.h
index 6e118799831c..2bf1199a0595 100644
--- a/arch/sh/include/asm/syscall_32.h
+++ b/arch/sh/include/asm/syscall_32.h
@@ -48,30 +48,16 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	/*
-	 * Do this simply for now. If we need to start supporting
-	 * fetching arguments from arbitrary indices, this will need some
-	 * extra logic. Presently there are no in-tree users that depend
-	 * on this behaviour.
-	 */
-	BUG_ON(i);
 
 	/* Argument pattern is: R4, R5, R6, R7, R0, R1 */
-	switch (n) {
-	case 6: args[5] = regs->regs[1];
-	case 5: args[4] = regs->regs[0];
-	case 4: args[3] = regs->regs[7];
-	case 3: args[2] = regs->regs[6];
-	case 2: args[1] = regs->regs[5];
-	case 1:	args[0] = regs->regs[4];
-	case 0:
-		break;
-	default:
-		BUG();
-	}
+	args[5] = regs->regs[1];
+	args[4] = regs->regs[0];
+	args[3] = regs->regs[7];
+	args[2] = regs->regs[6];
+	args[1] = regs->regs[5];
+	args[0] = regs->regs[4];
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/sh/include/asm/syscall_64.h b/arch/sh/include/asm/syscall_64.h
index 43882580c7f9..4e8f6460c703 100644
--- a/arch/sh/include/asm/syscall_64.h
+++ b/arch/sh/include/asm/syscall_64.h
@@ -47,11 +47,9 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	memcpy(args, &regs->regs[2 + i], n * sizeof(args[0]));
+	memcpy(args, &regs->regs[2], 6 * sizeof(args[0]));
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/sparc/include/asm/syscall.h b/arch/sparc/include/asm/syscall.h
index 053989e3f6a6..872dfee852d6 100644
--- a/arch/sparc/include/asm/syscall.h
+++ b/arch/sparc/include/asm/syscall.h
@@ -96,11 +96,11 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 	int zero_extend = 0;
 	unsigned int j;
+	unsigned int n = 6;
 
 #ifdef CONFIG_SPARC64
 	if (test_tsk_thread_flag(task, TIF_32BIT))
@@ -108,7 +108,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
 #endif
 
 	for (j = 0; j < n; j++) {
-		unsigned long val = regs->u_regs[UREG_I0 + i + j];
+		unsigned long val = regs->u_regs[UREG_I0 + j];
 
 		if (zero_extend)
 			args[j] = (u32) val;
diff --git a/arch/um/include/asm/syscall-generic.h b/arch/um/include/asm/syscall-generic.h
index 9fb9cf8cd39a..25d00acd1322 100644
--- a/arch/um/include/asm/syscall-generic.h
+++ b/arch/um/include/asm/syscall-generic.h
@@ -53,43 +53,16 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 	const struct uml_pt_regs *r = &regs->regs;
 
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG1(r);
-	case 1:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG2(r);
-	case 2:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG3(r);
-	case 3:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG4(r);
-	case 4:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG5(r);
-	case 5:
-		if (!n--)
-			break;
-		*args++ = UPT_SYSCALL_ARG6(r);
-	case 6:
-		if (!n--)
-			break;
-	default:
-		BUG();
-		break;
-	}
+	*args++ = UPT_SYSCALL_ARG1(r);
+	*args++ = UPT_SYSCALL_ARG2(r);
+	*args++ = UPT_SYSCALL_ARG3(r);
+	*args++ = UPT_SYSCALL_ARG4(r);
+	*args++ = UPT_SYSCALL_ARG5(r);
+	*args   = UPT_SYSCALL_ARG6(r);
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d653139857af..8dbb5c379450 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -91,11 +91,9 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	memcpy(args, &regs->bx + i, n * sizeof(args[0]));
+	memcpy(args, &regs->bx, 6 * sizeof(args[0]));
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
@@ -116,63 +114,26 @@ static inline int syscall_get_arch(void)
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 # ifdef CONFIG_IA32_EMULATION
-	if (task->thread_info.status & TS_COMPAT)
-		switch (i) {
-		case 0:
-			if (!n--) break;
-			*args++ = regs->bx;
-		case 1:
-			if (!n--) break;
-			*args++ = regs->cx;
-		case 2:
-			if (!n--) break;
-			*args++ = regs->dx;
-		case 3:
-			if (!n--) break;
-			*args++ = regs->si;
-		case 4:
-			if (!n--) break;
-			*args++ = regs->di;
-		case 5:
-			if (!n--) break;
-			*args++ = regs->bp;
-		case 6:
-			if (!n--) break;
-		default:
-			BUG();
-			break;
-		}
-	else
+	if (task->thread_info.status & TS_COMPAT) {
+		*args++ = regs->bx;
+		*args++ = regs->cx;
+		*args++ = regs->dx;
+		*args++ = regs->si;
+		*args++ = regs->di;
+		*args   = regs->bp;
+	} else
 # endif
-		switch (i) {
-		case 0:
-			if (!n--) break;
-			*args++ = regs->di;
-		case 1:
-			if (!n--) break;
-			*args++ = regs->si;
-		case 2:
-			if (!n--) break;
-			*args++ = regs->dx;
-		case 3:
-			if (!n--) break;
-			*args++ = regs->r10;
-		case 4:
-			if (!n--) break;
-			*args++ = regs->r8;
-		case 5:
-			if (!n--) break;
-			*args++ = regs->r9;
-		case 6:
-			if (!n--) break;
-		default:
-			BUG();
-			break;
-		}
+	{
+		*args++ = regs->di;
+		*args++ = regs->si;
+		*args++ = regs->dx;
+		*args++ = regs->r10;
+		*args++ = regs->r8;
+		*args   = regs->r9;
+	}
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/arch/xtensa/include/asm/syscall.h b/arch/xtensa/include/asm/syscall.h
index a168bf81c7f4..1504ce9a233a 100644
--- a/arch/xtensa/include/asm/syscall.h
+++ b/arch/xtensa/include/asm/syscall.h
@@ -59,23 +59,13 @@ static inline void syscall_set_return_value(struct task_struct *task,
 
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
 	static const unsigned int reg[] = XTENSA_SYSCALL_ARGUMENT_REGS;
-	unsigned int j;
-
-	if (n == 0)
-		return;
-
-	WARN_ON_ONCE(i + n > SYSCALL_MAX_ARGS);
+	unsigned int i;
 
-	for (j = 0; j < n; ++j) {
-		if (i + j < SYSCALL_MAX_ARGS)
-			args[j] = regs->areg[reg[i + j]];
-		else
-			args[j] = 0;
-	}
+	for (i = 0; i < 6; ++i)
+		args[i] = regs->areg[reg[i]];
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 0c938a4354f6..269e9412ef42 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -105,21 +105,16 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  * syscall_get_arguments - extract system call parameter values
  * @task:	task of interest, must be blocked
  * @regs:	task_pt_regs() of @task
- * @i:		argument index [0,5]
- * @n:		number of arguments; n+i must be [1,6].
  * @args:	array filled with argument values
  *
- * Fetches @n arguments to the system call starting with the @i'th argument
- * (from 0 through 5).  Argument @i is stored in @args[0], and so on.
- * An arch inline version is probably optimal when @i and @n are constants.
+ * Fetches 6 arguments to the system call.  First argument is stored in
+*  @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
- * It's invalid to call this with @i + @n > 6; we only support system calls
- * taking up to 6 arguments.
  */
 void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
-			   unsigned int i, unsigned int n, unsigned long *args);
+			   unsigned long *args);
 
 /**
  * syscall_set_arguments - change system call parameter value
diff --git a/include/trace/events/syscalls.h b/include/trace/events/syscalls.h
index 44a3259ed4a5..b6e0cbc2c71f 100644
--- a/include/trace/events/syscalls.h
+++ b/include/trace/events/syscalls.h
@@ -28,7 +28,7 @@ TRACE_EVENT_FN(sys_enter,
 
 	TP_fast_assign(
 		__entry->id	= id;
-		syscall_get_arguments(current, regs, 0, 6, __entry->args);
+		syscall_get_arguments(current, regs, __entry->args);
 	),
 
 	TP_printk("NR %ld (%lx, %lx, %lx, %lx, %lx, %lx)",
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 54a0347ca812..df27e499956a 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -149,7 +149,7 @@ static void populate_seccomp_data(struct seccomp_data *sd)
 
 	sd->nr = syscall_get_nr(task, regs);
 	sd->arch = syscall_get_arch();
-	syscall_get_arguments(task, regs, 0, 6, args);
+	syscall_get_arguments(task, regs, args);
 	sd->args[0] = args[0];
 	sd->args[1] = args[1];
 	sd->args[2] = args[2];
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index e9f5bbbad6d9..fa8fbff736d6 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -348,7 +348,7 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 
 	entry = ring_buffer_event_data(event);
 	entry->nr = syscall_nr;
-	syscall_get_arguments(current, regs, 0, 6, args);
+	syscall_get_arguments(current, regs, args);
 	memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
 	event_trigger_unlock_commit(trace_file, buffer, event, entry,
@@ -616,7 +616,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 		return;
 
 	rec->nr = syscall_nr;
-	syscall_get_arguments(current, regs, 0, 6, args);
+	syscall_get_arguments(current, regs, args);
 	memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 
 	if ((valid_prog_array &&
diff --git a/lib/syscall.c b/lib/syscall.c
index e8467e17b9a2..fb328e7ccb08 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -27,7 +27,7 @@ static int collect_syscall(struct task_struct *target, struct syscall_info *info
 
 	info->data.nr = syscall_get_nr(target, regs);
 	if (info->data.nr != -1L)
-		syscall_get_arguments(target, regs, 0, 6,
+		syscall_get_arguments(target, regs,
 				      (unsigned long *)&info->data.args[0]);
 
 	put_task_stack(target);
-- 
2.20.1

[RFC][PATCH 4/4 v2] syscalls: Remove start and number from syscall_set_arguments() args

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

After removing the start and count arguments of syscall_get_arguments() it
seems reasonable to remove them from syscall_set_arguments(). Note, as of
today, there are no users of syscall_set_arguments(). But we are told that
there will be soon. But for now, at least make it consistent with
syscall_get_arguments().

Link: http://lkml.kernel.org/r/20190327222014.GA32540@altlinux.org

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Dave Martin <dave.martin@arm.com>
Cc: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-hexagon@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecores.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 arch/arm/include/asm/syscall.h        | 22 ++-------
 arch/arm64/include/asm/syscall.h      | 22 ++-------
 arch/c6x/include/asm/syscall.h        | 38 +++------------
 arch/csky/include/asm/syscall.h       | 13 ++---
 arch/ia64/include/asm/syscall.h       | 10 ++--
 arch/ia64/kernel/ptrace.c             |  7 ++-
 arch/microblaze/include/asm/syscall.h |  4 +-
 arch/nds32/include/asm/syscall.h      | 29 ++---------
 arch/nios2/include/asm/syscall.h      | 42 +++-------------
 arch/openrisc/include/asm/syscall.h   |  6 +--
 arch/powerpc/include/asm/syscall.h    |  7 +--
 arch/riscv/include/asm/syscall.h      | 12 ++---
 arch/s390/include/asm/syscall.h       | 11 ++---
 arch/sh/include/asm/syscall_32.h      | 21 +++-----
 arch/sh/include/asm/syscall_64.h      |  4 +-
 arch/sparc/include/asm/syscall.h      |  7 ++-
 arch/um/include/asm/syscall-generic.h | 39 +++------------
 arch/x86/include/asm/syscall.h        | 69 +++++++--------------------
 arch/xtensa/include/asm/syscall.h     | 17 ++-----
 include/asm-generic/syscall.h         | 10 +---
 20 files changed, 88 insertions(+), 302 deletions(-)

diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index db969a2972ae..080ce70cab12 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -65,26 +65,12 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	if (n == 0)
-		return;
-
-	if (i + n > SYSCALL_MAX_ARGS) {
-		pr_warn("%s called with max args %d, handling only %d\n",
-			__func__, i + n, SYSCALL_MAX_ARGS);
-		n = SYSCALL_MAX_ARGS - i;
-	}
-
-	if (i == 0) {
-		regs->ARM_ORIG_r0 = args[0];
-		args++;
-		i++;
-		n--;
-	}
-
-	memcpy(&regs->ARM_r0 + i, args, n * sizeof(args[0]));
+	regs->ARM_ORIG_r0 = args[0];
+	args++;
+
+	memcpy(&regs->ARM_r0 + 1, args, 5 * sizeof(args[0]));
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 55b2dab21023..a179df3674a1 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -75,26 +75,12 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	if (n == 0)
-		return;
-
-	if (i + n > SYSCALL_MAX_ARGS) {
-		pr_warning("%s called with max args %d, handling only %d\n",
-			   __func__, i + n, SYSCALL_MAX_ARGS);
-		n = SYSCALL_MAX_ARGS - i;
-	}
-
-	if (i == 0) {
-		regs->orig_x0 = args[0];
-		args++;
-		i++;
-		n--;
-	}
-
-	memcpy(&regs->regs[i], args, n * sizeof(args[0]));
+	regs->orig_x0 = args[0];
+	args++;
+
+	memcpy(&regs->regs[1], args, 5 * sizeof(args[0]));
 }
 
 /*
diff --git a/arch/c6x/include/asm/syscall.h b/arch/c6x/include/asm/syscall.h
index 06db3251926b..15ba8599858e 100644
--- a/arch/c6x/include/asm/syscall.h
+++ b/arch/c6x/include/asm/syscall.h
@@ -59,40 +59,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		regs->a4 = *args++;
-	case 1:
-		if (!n--)
-			break;
-		regs->b4 = *args++;
-	case 2:
-		if (!n--)
-			break;
-		regs->a6 = *args++;
-	case 3:
-		if (!n--)
-			break;
-		regs->b6 = *args++;
-	case 4:
-		if (!n--)
-			break;
-		regs->a8 = *args++;
-	case 5:
-		if (!n--)
-			break;
-		regs->a9 = *args++;
-	case 6:
-		if (!n)
-			break;
-	default:
-		BUG();
-	}
+	regs->a4 = *args++;
+	regs->b4 = *args++;
+	regs->a6 = *args++;
+	regs->b6 = *args++;
+	regs->a8 = *args++;
+	regs->a9 = *args;
 }
 
 #endif /* __ASM_C6X_SYSCALLS_H */
diff --git a/arch/csky/include/asm/syscall.h b/arch/csky/include/asm/syscall.h
index 5cc0b8283a69..34c02d6bb973 100644
--- a/arch/csky/include/asm/syscall.h
+++ b/arch/csky/include/asm/syscall.h
@@ -52,16 +52,11 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 
 static inline void
 syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, const unsigned long *args)
+		      const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	if (i == 0) {
-		regs->orig_a0 = args[0];
-		args++;
-		i++;
-		n--;
-	}
-	memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
+	regs->orig_a0 = args[0];
+	args++;
+	memcpy(&regs->a1 + sizeof(regs->a1), args, 5 * sizeof(regs->a0));
 }
 
 static inline int
diff --git a/arch/ia64/include/asm/syscall.h b/arch/ia64/include/asm/syscall.h
index 8204c1ff70ce..0d9e7fab4a79 100644
--- a/arch/ia64/include/asm/syscall.h
+++ b/arch/ia64/include/asm/syscall.h
@@ -59,23 +59,19 @@ static inline void syscall_set_return_value(struct task_struct *task,
 }
 
 extern void ia64_syscall_get_set_arguments(struct task_struct *task,
-	struct pt_regs *regs, unsigned int i, unsigned int n,
-	unsigned long *args, int rw);
+	struct pt_regs *regs, unsigned long *args, int rw);
 static inline void syscall_get_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
 					 unsigned long *args)
 {
-	ia64_syscall_get_set_arguments(task, regs, 0, 6, args, 0);
+	ia64_syscall_get_set_arguments(task, regs, args, 0);
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	ia64_syscall_get_set_arguments(task, regs, i, n, args, 1);
+	ia64_syscall_get_set_arguments(task, regs, args, 1);
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 6d50ede0ed69..bf9c24d9ce84 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -2179,12 +2179,11 @@ static void syscall_get_set_args_cb(struct unw_frame_info *info, void *data)
 }
 
 void ia64_syscall_get_set_arguments(struct task_struct *task,
-	struct pt_regs *regs, unsigned int i, unsigned int n,
-	unsigned long *args, int rw)
+	struct pt_regs *regs, unsigned long *args, int rw)
 {
 	struct syscall_get_set_args data = {
-		.i = i,
-		.n = n,
+		.i = 0,
+		.n = 6,
 		.args = args,
 		.regs = regs,
 		.rw = rw,
diff --git a/arch/microblaze/include/asm/syscall.h b/arch/microblaze/include/asm/syscall.h
index 4b23e44e5c3c..833d3a53dab3 100644
--- a/arch/microblaze/include/asm/syscall.h
+++ b/arch/microblaze/include/asm/syscall.h
@@ -93,9 +93,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
+	unsigned int i = 0;
+	unsigned int n = 6;
+
 	while (n--)
 		microblaze_set_syscall_arg(regs, i++, *args++);
 }
diff --git a/arch/nds32/include/asm/syscall.h b/arch/nds32/include/asm/syscall.h
index 89a6ec8731d8..671ebd357496 100644
--- a/arch/nds32/include/asm/syscall.h
+++ b/arch/nds32/include/asm/syscall.h
@@ -129,39 +129,20 @@ void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  * syscall_set_arguments - change system call parameter value
  * @task:	task of interest, must be in system call entry tracing
  * @regs:	task_pt_regs() of @task
- * @i:		argument index [0,5]
- * @n:		number of arguments; n+i must be [1,6].
  * @args:	array of argument values to store
  *
- * Changes @n arguments to the system call starting with the @i'th argument.
- * Argument @i gets value @args[0], and so on.
- * An arch inline version is probably optimal when @i and @n are constants.
+ * Changes 6 arguments to the system call. The first argument gets value
+ * @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
- * It's invalid to call this with @i + @n > 6; we only support system calls
- * taking up to 6 arguments.
  */
 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
-			   unsigned int i, unsigned int n,
 			   const unsigned long *args)
 {
-	if (n == 0)
-		return;
-
-	if (i + n > SYSCALL_MAX_ARGS) {
-		pr_warn("%s called with max args %d, handling only %d\n",
-			__func__, i + n, SYSCALL_MAX_ARGS);
-		n = SYSCALL_MAX_ARGS - i;
-	}
-
-	if (i == 0) {
-		regs->orig_r0 = args[0];
-		args++;
-		i++;
-		n--;
-	}
+	regs->orig_r0 = args[0];
+	args++;
 
-	memcpy(&regs->uregs[0] + i, args, n * sizeof(args[0]));
+	memcpy(&regs->uregs[0] + 1, args, 5 * sizeof(args[0]));
 }
 #endif /* _ASM_NDS32_SYSCALL_H */
diff --git a/arch/nios2/include/asm/syscall.h b/arch/nios2/include/asm/syscall.h
index 792bd449d839..d7624ed06efb 100644
--- a/arch/nios2/include/asm/syscall.h
+++ b/arch/nios2/include/asm/syscall.h
@@ -69,42 +69,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,
-	struct pt_regs *regs, unsigned int i, unsigned int n,
-	const unsigned long *args)
+	struct pt_regs *regs, const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		regs->r4 = *args++;
-	case 1:
-		if (!n--)
-			break;
-		regs->r5 = *args++;
-	case 2:
-		if (!n--)
-			break;
-		regs->r6 = *args++;
-	case 3:
-		if (!n--)
-			break;
-		regs->r7 = *args++;
-	case 4:
-		if (!n--)
-			break;
-		regs->r8 = *args++;
-	case 5:
-		if (!n--)
-			break;
-		regs->r9 = *args++;
-	case 6:
-		if (!n)
-			break;
-	default:
-		BUG();
-	}
+	regs->r4 = *args++;
+	regs->r5 = *args++;
+	regs->r6 = *args++;
+	regs->r7 = *args++;
+	regs->r8 = *args++;
+	regs->r9 = *args;
 }
 
 #endif
diff --git a/arch/openrisc/include/asm/syscall.h b/arch/openrisc/include/asm/syscall.h
index 72607860cd55..b4ff07c1baed 100644
--- a/arch/openrisc/include/asm/syscall.h
+++ b/arch/openrisc/include/asm/syscall.h
@@ -63,11 +63,9 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
 
 static inline void
 syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
-		      unsigned int i, unsigned int n, const unsigned long *args)
+		      const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-
-	memcpy(&regs->gpr[3 + i], args, n * sizeof(args[0]));
+	memcpy(&regs->gpr[3], args, 6 * sizeof(args[0]));
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 5c9b9dc82b7e..1243045bad2d 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -86,15 +86,12 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	memcpy(&regs->gpr[3 + i], args, n * sizeof(args[0]));
+	memcpy(&regs->gpr[3], args, 6 * sizeof(args[0]));
 
 	/* Also copy the first argument into orig_gpr3 */
-	if (i == 0 && n > 0)
-		regs->orig_gpr3 = args[0];
+	regs->orig_gpr3 = args[0];
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index 85a31dd0f2ba..7321644be1cf 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -81,17 +81,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-        if (i == 0) {
-                regs->orig_a0 = args[0];
-                args++;
-                i++;
-                n--;
-        }
-	memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
+	regs->orig_a0 = args[0];
+	args++;
+	memcpy(&regs->a1 + sizeof(regs->a1), args, 5 * sizeof(regs->a0));
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index ee0b1f6aa36d..59c3e91f2cdb 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -74,15 +74,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
+	unsigned int n = 6;
+
 	while (n-- > 0)
-		if (i + n > 0)
-			regs->gprs[2 + i + n] = args[n];
-	if (i == 0)
-		regs->orig_gpr2 = args[0];
+		if (n > 0)
+			regs->gprs[2 + n] = args[n];
+	regs->orig_gpr2 = args[0];
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/sh/include/asm/syscall_32.h b/arch/sh/include/asm/syscall_32.h
index 2bf1199a0595..8c9d7e5e5dcc 100644
--- a/arch/sh/include/asm/syscall_32.h
+++ b/arch/sh/include/asm/syscall_32.h
@@ -62,23 +62,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	/* Same note as above applies */
-	BUG_ON(i);
-
-	switch (n) {
-	case 6: regs->regs[1] = args[5];
-	case 5: regs->regs[0] = args[4];
-	case 4: regs->regs[7] = args[3];
-	case 3: regs->regs[6] = args[2];
-	case 2: regs->regs[5] = args[1];
-	case 1: regs->regs[4] = args[0];
-		break;
-	default:
-		BUG();
-	}
+	regs->regs[1] = args[5];
+	regs->regs[0] = args[4];
+	regs->regs[7] = args[3];
+	regs->regs[6] = args[2];
+	regs->regs[5] = args[1];
+	regs->regs[4] = args[0];
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/sh/include/asm/syscall_64.h b/arch/sh/include/asm/syscall_64.h
index 4e8f6460c703..22fad97da066 100644
--- a/arch/sh/include/asm/syscall_64.h
+++ b/arch/sh/include/asm/syscall_64.h
@@ -54,11 +54,9 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	BUG_ON(i + n > 6);
-	memcpy(&regs->regs[2 + i], args, n * sizeof(args[0]));
+	memcpy(&regs->regs[2], args, 6 * sizeof(args[0]));
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/sparc/include/asm/syscall.h b/arch/sparc/include/asm/syscall.h
index 872dfee852d6..4d075434e816 100644
--- a/arch/sparc/include/asm/syscall.h
+++ b/arch/sparc/include/asm/syscall.h
@@ -119,13 +119,12 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
-	unsigned int j;
+	unsigned int i;
 
-	for (j = 0; j < n; j++)
-		regs->u_regs[UREG_I0 + i + j] = args[j];
+	for (i = 0; i < 6; i++)
+		regs->u_regs[UREG_I0 + i] = args[i];
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/um/include/asm/syscall-generic.h b/arch/um/include/asm/syscall-generic.h
index 25d00acd1322..98e50c50c12e 100644
--- a/arch/um/include/asm/syscall-generic.h
+++ b/arch/um/include/asm/syscall-generic.h
@@ -67,43 +67,16 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
 	struct uml_pt_regs *r = &regs->regs;
 
-	switch (i) {
-	case 0:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG1(r) = *args++;
-	case 1:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG2(r) = *args++;
-	case 2:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG3(r) = *args++;
-	case 3:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG4(r) = *args++;
-	case 4:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG5(r) = *args++;
-	case 5:
-		if (!n--)
-			break;
-		UPT_SYSCALL_ARG6(r) = *args++;
-	case 6:
-		if (!n--)
-			break;
-	default:
-		BUG();
-		break;
-	}
+	UPT_SYSCALL_ARG1(r) = *args++;
+	UPT_SYSCALL_ARG2(r) = *args++;
+	UPT_SYSCALL_ARG3(r) = *args++;
+	UPT_SYSCALL_ARG4(r) = *args++;
+	UPT_SYSCALL_ARG5(r) = *args++;
+	UPT_SYSCALL_ARG6(r) = *args;
 }
 
 /* See arch/x86/um/asm/syscall.h for syscall_get_arch() definition. */
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index 8dbb5c379450..4c305471ec33 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -138,63 +138,26 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
 # ifdef CONFIG_IA32_EMULATION
-	if (task->thread_info.status & TS_COMPAT)
-		switch (i) {
-		case 0:
-			if (!n--) break;
-			regs->bx = *args++;
-		case 1:
-			if (!n--) break;
-			regs->cx = *args++;
-		case 2:
-			if (!n--) break;
-			regs->dx = *args++;
-		case 3:
-			if (!n--) break;
-			regs->si = *args++;
-		case 4:
-			if (!n--) break;
-			regs->di = *args++;
-		case 5:
-			if (!n--) break;
-			regs->bp = *args++;
-		case 6:
-			if (!n--) break;
-		default:
-			BUG();
-			break;
-		}
-	else
+	if (task->thread_info.status & TS_COMPAT) {
+		regs->bx = *args++;
+		regs->cx = *args++;
+		regs->dx = *args++;
+		regs->si = *args++;
+		regs->di = *args++;
+		regs->bp = *args;
+	} else
 # endif
-		switch (i) {
-		case 0:
-			if (!n--) break;
-			regs->di = *args++;
-		case 1:
-			if (!n--) break;
-			regs->si = *args++;
-		case 2:
-			if (!n--) break;
-			regs->dx = *args++;
-		case 3:
-			if (!n--) break;
-			regs->r10 = *args++;
-		case 4:
-			if (!n--) break;
-			regs->r8 = *args++;
-		case 5:
-			if (!n--) break;
-			regs->r9 = *args++;
-		case 6:
-			if (!n--) break;
-		default:
-			BUG();
-			break;
-		}
+	{
+		regs->di = *args++;
+		regs->si = *args++;
+		regs->dx = *args++;
+		regs->r10 = *args++;
+		regs->r8 = *args++;
+		regs->r9 = *args;
+	}
 }
 
 static inline int syscall_get_arch(void)
diff --git a/arch/xtensa/include/asm/syscall.h b/arch/xtensa/include/asm/syscall.h
index 1504ce9a233a..91dc06d58060 100644
--- a/arch/xtensa/include/asm/syscall.h
+++ b/arch/xtensa/include/asm/syscall.h
@@ -70,24 +70,13 @@ static inline void syscall_get_arguments(struct task_struct *task,
 
 static inline void syscall_set_arguments(struct task_struct *task,
 					 struct pt_regs *regs,
-					 unsigned int i, unsigned int n,
 					 const unsigned long *args)
 {
 	static const unsigned int reg[] = XTENSA_SYSCALL_ARGUMENT_REGS;
-	unsigned int j;
-
-	if (n == 0)
-		return;
-
-	if (WARN_ON_ONCE(i + n > SYSCALL_MAX_ARGS)) {
-		if (i < SYSCALL_MAX_ARGS)
-			n = SYSCALL_MAX_ARGS - i;
-		else
-			return;
-	}
+	unsigned int i;
 
-	for (j = 0; j < n; ++j)
-		regs->areg[reg[i + j]] = args[j];
+	for (i = 0; i < 6; ++i)
+		regs->areg[reg[i]] = args[i];
 }
 
 asmlinkage long xtensa_rt_sigreturn(struct pt_regs*);
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 269e9412ef42..b88239e9efe4 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -120,21 +120,15 @@ void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  * syscall_set_arguments - change system call parameter value
  * @task:	task of interest, must be in system call entry tracing
  * @regs:	task_pt_regs() of @task
- * @i:		argument index [0,5]
- * @n:		number of arguments; n+i must be [1,6].
  * @args:	array of argument values to store
  *
- * Changes @n arguments to the system call starting with the @i'th argument.
- * Argument @i gets value @args[0], and so on.
- * An arch inline version is probably optimal when @i and @n are constants.
+ * Changes 6 arguments to the system call.
+ * The first argument gets value @args[0], and so on.
  *
  * It's only valid to call this when @task is stopped for tracing on
  * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
- * It's invalid to call this with @i + @n > 6; we only support system calls
- * taking up to 6 arguments.
  */
 void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
-			   unsigned int i, unsigned int n,
 			   const unsigned long *args);
 
 /**
-- 
2.20.1

Re: [RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Linus Torvalds]

The whole series looks fine to me.

I still suspect that we should just remove the syscall_set_arguments()
thing entirely, but even without that, the cleanup of the calling
convention is at least an improvement.

                     Linus

Re: [RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Steven Rostedt]

On Fri, 29 Mar 2019 10:24:58 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> The whole series looks fine to me.

Great! I may just send a pull request to you, after some fixes (see
below).

> 
> I still suspect that we should just remove the syscall_set_arguments()
> thing entirely, but even without that, the cleanup of the calling
> convention is at least an improvement.

I'll keep it around for now, but this should go as a warning to Dmitry,
to get something using it soon, or they may be dropped.

Also, Dmitry found a few bugs with the current
syscall_set/get_arguments() on some of the archs (riscv and csky). Which
I'll add at the front of this series and update my changes to keep the
same logic.

Then I'll post a non RFC version.

-- Steve

Re: [RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Linus Torvalds]

On Fri, Mar 29, 2019 at 10:40 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> I'll keep it around for now, but this should go as a warning to Dmitry,
> to get something using it soon, or they may be dropped.

I don't think _that_ is the argument.

Quite the reverse: nobody has ever used it, why have it around, and
much less try to hurry some new pointless user to use it?

The "get system call arguments" code at least can be used somewhat
generically for things like tracing and strace.

The "set system call arguments" can NOT.

Anybody who sets system call arguments had better intimately know the
details anyway, and any user code has to have any legacy ptrace
interface anyway for all but the newest kernels.

So I will just say "NO". No new stupid interface that doesn't have a
truly immensely convincing reason for it.

And definitely not hurried along by "nobody has ever usefully done
this before and now people are noticing how bad the interfaces are, so
let's cobble some sh*t together quickly".

                     Linus

Re: [RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Dmitry V. Levin]

[-- Attachment #1: Type: text/plain, Size: 2142 bytes --]

On Fri, Mar 29, 2019 at 11:12:18AM -0700, Linus Torvalds wrote:
> On Fri, Mar 29, 2019 at 10:40 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > I'll keep it around for now, but this should go as a warning to Dmitry,
> > to get something using it soon, or they may be dropped.
> 
> I don't think _that_ is the argument.
> 
> Quite the reverse: nobody has ever used it, why have it around, and
> much less try to hurry some new pointless user to use it?
> 
> The "get system call arguments" code at least can be used somewhat
> generically for things like tracing and strace.
> 
> The "set system call arguments" can NOT.
> 
> Anybody who sets system call arguments had better intimately know the
> details anyway, and any user code has to have any legacy ptrace
> interface anyway for all but the newest kernels.

In strace we have a feature called system call tampering.
Initially limited to system call number and return code tampering,
it's being extended to tamper with system call arguments as well.

Currently it's implemented in strace using traditional
PTRACE_SETREGSET/PTRACE_SETREGS/PTRACE_POKEUSER interfaces.
These interfaces indeed require intimate knowledge of the target
architecture.  Fortunately, strace already has this intimate knowledge,
but the corresponding code would be much more trivial if an
architecture-agnostic ptrace interface for setting syscall info
existed in the kernel.

I didn't plan to start the discussion about this new ptrace command
before PTRACE_GET_SYSCALL_INFO [1] finally landed into the kernel.

For us userspace people it takes a lot of time not only to get a new
kernel interface accepted, but even to reintroduce an old internal kernel
interface that was removed due to lack of users.  For example, it took me
roughly 4 months to get a relatively simple partial revert of commit
5e937a9ae913 accepted into linux-next.

This was the reason why I asked to delay the removal of
syscall_set_arguments() until PTRACE_GET_SYSCALL_INFO
is merged into the kernel.

[1] https://lore.kernel.org/lkml/20190322041409.GA27266@altlinux.org/


-- 
ldv

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

Re: [RFC][PATCH 0/4 v2] sycalls: Remove args i and n from syscall_get_arguments()

[Palmer Dabbelt]

On Fri, 29 Mar 2019 10:40:45 PDT (-0700), rostedt@goodmis.org wrote:
> On Fri, 29 Mar 2019 10:24:58 -0700
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
>> The whole series looks fine to me.
>
> Great! I may just send a pull request to you, after some fixes (see
> below).
>
>>
>> I still suspect that we should just remove the syscall_set_arguments()
>> thing entirely, but even without that, the cleanup of the calling
>> convention is at least an improvement.
>
> I'll keep it around for now, but this should go as a warning to Dmitry,
> to get something using it soon, or they may be dropped.
>
> Also, Dmitry found a few bugs with the current
> syscall_set/get_arguments() on some of the archs (riscv and csky). Which
> I'll add at the front of this series and update my changes to keep the
> same logic.

Thanks.  I'm happy to have you take the RISC-V fix through your tree.

>
> Then I'll post a non RFC version.
>
> -- Steve