generic compat_sys_sigaltstack()

Again, conditional on CONFIG_GENERIC_SIGALTSTACK
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/x86/ia32/ia32_signal.c

@@ -136,52 +136,6 @@ asmlinkage long sys32_sigsuspend(int history0, int history1, old_sigset_t mask)
 	return sigsuspend(&blocked);
 }
 
-asmlinkage long sys32_sigaltstack(const stack_ia32_t __user *uss_ptr,
-				  stack_ia32_t __user *uoss_ptr,
-				  struct pt_regs *regs)
-{
-	stack_t uss, uoss;
-	int ret, err = 0;
-	mm_segment_t seg;
-
-	if (uss_ptr) {
-		u32 ptr;
-
-		memset(&uss, 0, sizeof(stack_t));
-		if (!access_ok(VERIFY_READ, uss_ptr, sizeof(stack_ia32_t)))
-			return -EFAULT;
-
-		get_user_try {
-			get_user_ex(ptr, &uss_ptr->ss_sp);
-			get_user_ex(uss.ss_flags, &uss_ptr->ss_flags);
-			get_user_ex(uss.ss_size, &uss_ptr->ss_size);
-		} get_user_catch(err);
-
-		if (err)
-			return -EFAULT;
-		uss.ss_sp = compat_ptr(ptr);
-	}
-	seg = get_fs();
-	set_fs(KERNEL_DS);
-	ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
-			     (stack_t __force __user *) &uoss, regs->sp);
-	set_fs(seg);
-	if (ret >= 0 && uoss_ptr)  {
-		if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(stack_ia32_t)))
-			return -EFAULT;
-
-		put_user_try {
-			put_user_ex(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp);
-			put_user_ex(uoss.ss_flags, &uoss_ptr->ss_flags);
-			put_user_ex(uoss.ss_size, &uoss_ptr->ss_size);
-		} put_user_catch(err);
-
-		if (err)
-			ret = -EFAULT;
-	}
-	return ret;
-}
-
 /*
  * Do a signal return; undo the signal stack.
  */
@@ -292,7 +246,6 @@ asmlinkage long sys32_rt_sigreturn(struct pt_regs *regs)
 	struct rt_sigframe_ia32 __user *frame;
 	sigset_t set;
 	unsigned int ax;
-	struct pt_regs tregs;
 
 	frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
 
@@ -306,8 +259,7 @@ asmlinkage long sys32_rt_sigreturn(struct pt_regs *regs)
 	if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 		goto badframe;
 
-	tregs = *regs;
-	if (sys32_sigaltstack(&frame->uc.uc_stack, NULL, &tregs) == -EFAULT)
+	if (compat_restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return ax;

arch/x86/ia32/ia32entry.S

@@ -464,7 +464,6 @@ GLOBAL(\label)
 
 	PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn, %rdi
 	PTREGSCALL stub32_sigreturn, sys32_sigreturn, %rdi
-	PTREGSCALL stub32_sigaltstack, sys32_sigaltstack, %rdx
 	PTREGSCALL stub32_execve, compat_sys_execve, %rcx
 	PTREGSCALL stub32_fork, sys_fork, %rdi
 	PTREGSCALL stub32_vfork, sys_vfork, %rdi

arch/x86/include/asm/ia32.h

@@ -29,16 +29,10 @@ struct old_sigaction32 {
 	unsigned int sa_restorer;	/* Another 32 bit pointer */
 };
 
-typedef struct sigaltstack_ia32 {
-	unsigned int	ss_sp;
-	int		ss_flags;
-	unsigned int	ss_size;
-} stack_ia32_t;
-
 struct ucontext_ia32 {
 	unsigned int	  uc_flags;
 	unsigned int 	  uc_link;
-	stack_ia32_t	  uc_stack;
+	compat_stack_t	  uc_stack;
 	struct sigcontext_ia32 uc_mcontext;
 	compat_sigset_t	  uc_sigmask;	/* mask last for extensibility */
 };
@@ -46,7 +40,7 @@ struct ucontext_ia32 {
 struct ucontext_x32 {
 	unsigned int	  uc_flags;
 	unsigned int 	  uc_link;
-	stack_ia32_t	  uc_stack;
+	compat_stack_t	  uc_stack;
 	unsigned int	  uc__pad0;     /* needed for alignment */
 	struct sigcontext uc_mcontext;  /* the 64-bit sigcontext type */
 	compat_sigset_t	  uc_sigmask;	/* mask last for extensibility */

arch/x86/include/asm/sys_ia32.h

@@ -69,8 +69,6 @@ asmlinkage long sys32_fallocate(int, int, unsigned,
 
 /* ia32/ia32_signal.c */
 asmlinkage long sys32_sigsuspend(int, int, old_sigset_t);
-asmlinkage long sys32_sigaltstack(const stack_ia32_t __user *,
-				  stack_ia32_t __user *, struct pt_regs *);
 asmlinkage long sys32_sigreturn(struct pt_regs *);
 asmlinkage long sys32_rt_sigreturn(struct pt_regs *);
 

arch/x86/kernel/entry_64.S

@@ -912,8 +912,6 @@ ENTRY(stub_rt_sigreturn)
 END(stub_rt_sigreturn)
 
 #ifdef CONFIG_X86_X32_ABI
-	PTREGSCALL stub_x32_sigaltstack, sys32_sigaltstack, %rdx
-
 ENTRY(stub_x32_rt_sigreturn)
 	CFI_STARTPROC
 	addq $8, %rsp

arch/x86/kernel/signal.c

@@ -857,7 +857,6 @@ asmlinkage long sys32_x32_rt_sigreturn(struct pt_regs *regs)
 	struct rt_sigframe_x32 __user *frame;
 	sigset_t set;
 	unsigned long ax;
-	struct pt_regs tregs;
 
 	frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 
@@ -871,8 +870,7 @@ asmlinkage long sys32_x32_rt_sigreturn(struct pt_regs *regs)
 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 		goto badframe;
 
-	tregs = *regs;
-	if (sys32_sigaltstack(&frame->uc.uc_stack, NULL, &tregs) == -EFAULT)
+	if (compat_restore_altstack(&frame->uc.uc_stack))
 		goto badframe;
 
 	return ax;

arch/x86/syscalls/syscall_32.tbl

@@ -192,7 +192,7 @@
 183	i386	getcwd			sys_getcwd
 184	i386	capget			sys_capget
 185	i386	capset			sys_capset
-186	i386	sigaltstack		sys_sigaltstack			stub32_sigaltstack
+186	i386	sigaltstack		sys_sigaltstack			compat_sys_sigaltstack
 187	i386	sendfile		sys_sendfile			sys32_sendfile
 188	i386	getpmsg
 189	i386	putpmsg

arch/x86/syscalls/syscall_64.tbl

@@ -337,7 +337,7 @@
 522	x32	rt_sigpending		sys32_rt_sigpending
 523	x32	rt_sigtimedwait		compat_sys_rt_sigtimedwait
 524	x32	rt_sigqueueinfo		sys32_rt_sigqueueinfo
-525	x32	sigaltstack		stub_x32_sigaltstack
+525	x32	sigaltstack		compat_sys_sigaltstack
 526	x32	timer_create		compat_sys_timer_create
 527	x32	mq_notify		compat_sys_mq_notify
 528	x32	kexec_load		compat_sys_kexec_load

include/linux/compat.h

@@ -68,6 +68,16 @@
 #ifndef compat_user_stack_pointer
 #define compat_user_stack_pointer() current_user_stack_pointer()
 #endif
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+#ifndef compat_sigaltstack	/* we'll need that for MIPS */
+typedef struct compat_sigaltstack {
+	compat_uptr_t			ss_sp;
+	int				ss_flags;
+	compat_size_t			ss_size;
+} compat_stack_t;
+#endif
+#endif
+
 #define compat_jiffies_to_clock_t(x)	\
 		(((unsigned long)(x) * COMPAT_USER_HZ) / HZ)
 
@@ -632,6 +642,12 @@ asmlinkage ssize_t compat_sys_process_vm_writev(compat_pid_t pid,
 
 asmlinkage long compat_sys_sendfile(int out_fd, int in_fd,
 				    compat_off_t __user *offset, compat_size_t count);
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
+				       compat_stack_t __user *uoss_ptr);
+
+int compat_restore_altstack(const compat_stack_t __user *uss);
+#endif
 
 #else
 

kernel/signal.c

@@ -31,6 +31,7 @@
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
 #include <linux/uprobes.h>
+#include <linux/compat.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/signal.h>
 
@@ -3116,6 +3117,50 @@ int restore_altstack(const stack_t __user *uss)
 	return err == -EFAULT ? err : 0;
 }
 
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
+				       compat_stack_t __user *uoss_ptr)
+{
+	stack_t uss, uoss;
+	int ret;
+	mm_segment_t seg;
+
+	if (uss_ptr) {
+		compat_stack_t uss32;
+
+		memset(&uss, 0, sizeof(stack_t));
+		if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
+			return -EFAULT;
+		uss.ss_sp = compat_ptr(uss32.ss_sp);
+		uss.ss_flags = uss32.ss_flags;
+		uss.ss_size = uss32.ss_size;
+	}
+	seg = get_fs();
+	set_fs(KERNEL_DS);
+	ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
+			     (stack_t __force __user *) &uoss,
+			     compat_user_stack_pointer());
+	set_fs(seg);
+	if (ret >= 0 && uoss_ptr)  {
+		if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) ||
+		    __put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
+		    __put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
+		    __put_user(uoss.ss_size, &uoss_ptr->ss_size))
+			ret = -EFAULT;
+	}
+	return ret;
+}
+
+int compat_restore_altstack(const compat_stack_t __user *uss)
+{
+	int err = compat_sys_sigaltstack(uss, NULL);
+	/* squash all but -EFAULT for now */
+	return err == -EFAULT ? err : 0;
+}
+#endif
+#endif
+
 #ifdef __ARCH_WANT_SYS_SIGPENDING
 
 /**