x86: use regparm(3) for passed-in pt_regs pointer

Some syscalls need to access the pt_regs structure, either to copy
user register state or to modifiy it.  This patch adds stubs to load
the address of the pt_regs struct into the %eax register, and changes
the syscalls to take the pointer as an argument instead of relying on
the assumption that the pt_regs structure overlaps the function
arguments.

Drop the use of regparm(1) due to concern about gcc bugs, and to move
in the direction of the eventual removal of regparm(0) for asmlinkage.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 17 insertions, 10 deletions

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 5a9dcfb01f71..fec79ad85dc6 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -603,15 +603,21 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	return prev_p;
 }
 
-ptregscall int sys_fork(struct pt_regs *regs)
+int sys_fork(struct pt_regs *regs)
 {
 	return do_fork(SIGCHLD, regs->sp, regs, 0, NULL, NULL);
 }
 
-ptregscall int sys_clone(struct pt_regs *regs, unsigned long clone_flags,
-			 unsigned long newsp, int __user *parent_tidptr,
-			 unsigned long unused, int __user *child_tidptr)
+int sys_clone(struct pt_regs *regs)
 {
+	unsigned long clone_flags;
+	unsigned long newsp;
+	int __user *parent_tidptr, *child_tidptr;
+
+	clone_flags = regs->bx;
+	newsp = regs->cx;
+	parent_tidptr = (int __user *)regs->dx;
+	child_tidptr = (int __user *)regs->di;
 	if (!newsp)
 		newsp = regs->sp;
 	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
@@ -627,7 +633,7 @@ ptregscall int sys_clone(struct pt_regs *regs, unsigned long clone_flags,
  * do not have enough call-clobbered registers to hold all
  * the information you need.
  */
-ptregscall int sys_vfork(struct pt_regs *regs)
+int sys_vfork(struct pt_regs *regs)
 {
 	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->sp, regs, 0, NULL, NULL);
 }
@@ -635,18 +641,19 @@ ptregscall int sys_vfork(struct pt_regs *regs)
 /*
  * sys_execve() executes a new program.
  */
-ptregscall int sys_execve(struct pt_regs *regs, char __user *u_filename,
-			  char __user * __user *argv,
-			  char __user * __user *envp)
+int sys_execve(struct pt_regs *regs)
 {
 	int error;
 	char *filename;
 
-	filename = getname(u_filename);
+	filename = getname((char __user *) regs->bx);
 	error = PTR_ERR(filename);
 	if (IS_ERR(filename))
 		goto out;
-	error = do_execve(filename, argv, envp, regs);
+	error = do_execve(filename,
+			(char __user * __user *) regs->cx,
+			(char __user * __user *) regs->dx,
+			regs);
 	if (error == 0) {
 		/* Make sure we don't return using sysenter.. */
 		set_thread_flag(TIF_IRET);