um: add extended processor state save/restore support

This patch extends save_fp_registers() and restore_fp_registers() to use
PTRACE_GETREGSET and PTRACE_SETREGSET with the XSTATE note type, adding
support for new processor state extensions between context switches.

When the new ptrace requests are unavailable, it falls back to the old
PTRACE_GETFPREGS and PTRACE_SETFPREGS methods, which have been renamed to
save_i387_registers() and restore_i387_registers().

Now these functions expect *fp_regs to have the space of an _xstate struct.
Thus, this also makes ptrace in UML responde to PTRACE_GETFPREGS/_SETFPREG
requests with a user_i387_struct (thus independent from HOST_FP_SIZE), and
by calling save_i387_registers() and restore_i387_registers() instead of
the extended save_fp_registers() and restore_fp_registers() functions.
Signed-off-by: Eli Cooper <elicooper@gmx.com>

arch/um/include/shared/registers.h

@@ -9,6 +9,8 @@
 #include <sysdep/ptrace.h>
 #include <sysdep/archsetjmp.h>
 
+extern int save_i387_registers(int pid, unsigned long *fp_regs);
+extern int restore_i387_registers(int pid, unsigned long *fp_regs);
 extern int save_fp_registers(int pid, unsigned long *fp_regs);
 extern int restore_fp_registers(int pid, unsigned long *fp_regs);
 extern int save_fpx_registers(int pid, unsigned long *fp_regs);

arch/um/kernel/process.c

@@ -402,6 +402,6 @@ int elf_core_copy_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
 {
 	int cpu = current_thread_info()->cpu;
 
-	return save_fp_registers(userspace_pid[cpu], (unsigned long *) fpu);
+	return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
 }
 

arch/x86/um/os-Linux/registers.c

@@ -11,21 +11,56 @@
 #endif
 #include <longjmp.h>
 #include <sysdep/ptrace_user.h>
+#include <sys/uio.h>
+#include <asm/sigcontext.h>
+#include <linux/elf.h>
 
-int save_fp_registers(int pid, unsigned long *fp_regs)
+int have_xstate_support;
+
+int save_i387_registers(int pid, unsigned long *fp_regs)
 {
 	if (ptrace(PTRACE_GETFPREGS, pid, 0, fp_regs) < 0)
 		return -errno;
 	return 0;
 }
 
-int restore_fp_registers(int pid, unsigned long *fp_regs)
+int save_fp_registers(int pid, unsigned long *fp_regs)
+{
+	struct iovec iov;
+
+	if (have_xstate_support) {
+		iov.iov_base = fp_regs;
+		iov.iov_len = sizeof(struct _xstate);
+		if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+			return -errno;
+		return 0;
+	} else {
+		return save_i387_registers(pid, fp_regs);
+	}
+}
+
+int restore_i387_registers(int pid, unsigned long *fp_regs)
 {
 	if (ptrace(PTRACE_SETFPREGS, pid, 0, fp_regs) < 0)
 		return -errno;
 	return 0;
 }
 
+int restore_fp_registers(int pid, unsigned long *fp_regs)
+{
+	struct iovec iov;
+
+	if (have_xstate_support) {
+		iov.iov_base = fp_regs;
+		iov.iov_len = sizeof(struct _xstate);
+		if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+			return -errno;
+		return 0;
+	} else {
+		return restore_i387_registers(pid, fp_regs);
+	}
+}
+
 #ifdef __i386__
 int have_fpx_regs = 1;
 int save_fpx_registers(int pid, unsigned long *fp_regs)
@@ -85,6 +120,16 @@ int put_fp_registers(int pid, unsigned long *regs)
 	return restore_fp_registers(pid, regs);
 }
 
+void arch_init_registers(int pid)
+{
+	struct _xstate fp_regs;
+	struct iovec iov;
+
+	iov.iov_base = &fp_regs;
+	iov.iov_len = sizeof(struct _xstate);
+	if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
+		have_xstate_support = 1;
+}
 #endif
 
 unsigned long get_thread_reg(int reg, jmp_buf *buf)

arch/x86/um/ptrace_32.c

@@ -194,7 +194,8 @@ static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *c
 	int err, n, cpu = ((struct thread_info *) child->stack)->cpu;
 	struct user_i387_struct fpregs;
 
-	err = save_fp_registers(userspace_pid[cpu], (unsigned long *) &fpregs);
+	err = save_i387_registers(userspace_pid[cpu],
+				  (unsigned long *) &fpregs);
 	if (err)
 		return err;
 
@@ -214,7 +215,7 @@ static int set_fpregs(struct user_i387_struct __user *buf, struct task_struct *c
 	if (n > 0)
 		return -EFAULT;
 
-	return restore_fp_registers(userspace_pid[cpu],
+	return restore_i387_registers(userspace_pid[cpu],
 				    (unsigned long *) &fpregs);
 }
 

arch/x86/um/ptrace_64.c

@@ -222,14 +222,14 @@ int is_syscall(unsigned long addr)
 static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
 {
 	int err, n, cpu = ((struct thread_info *) child->stack)->cpu;
-	long fpregs[HOST_FP_SIZE];
+	struct user_i387_struct fpregs;
 
-	BUG_ON(sizeof(*buf) != sizeof(fpregs));
-	err = save_fp_registers(userspace_pid[cpu], fpregs);
+	err = save_i387_registers(userspace_pid[cpu],
+				  (unsigned long *) &fpregs);
 	if (err)
 		return err;
 
-	n = copy_to_user(buf, fpregs, sizeof(fpregs));
+	n = copy_to_user(buf, &fpregs, sizeof(fpregs));
 	if (n > 0)
 		return -EFAULT;
 
@@ -239,14 +239,14 @@ static int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *c
 static int set_fpregs(struct user_i387_struct __user *buf, struct task_struct *child)
 {
 	int n, cpu = ((struct thread_info *) child->stack)->cpu;
-	long fpregs[HOST_FP_SIZE];
+	struct user_i387_struct fpregs;
 
-	BUG_ON(sizeof(*buf) != sizeof(fpregs));
-	n = copy_from_user(fpregs, buf, sizeof(fpregs));
+	n = copy_from_user(&fpregs, buf, sizeof(fpregs));
 	if (n > 0)
 		return -EFAULT;
 
-	return restore_fp_registers(userspace_pid[cpu], fpregs);
+	return restore_i387_registers(userspace_pid[cpu],
+				      (unsigned long *) &fpregs);
 }
 
 long subarch_ptrace(struct task_struct *child, long request,

arch/x86/um/shared/sysdep/ptrace_64.h

@@ -57,8 +57,6 @@
 #define UPT_SYSCALL_ARG5(r) UPT_R8(r)
 #define UPT_SYSCALL_ARG6(r) UPT_R9(r)
 
-static inline void arch_init_registers(int pid)
-{
-}
+extern void arch_init_registers(int pid);
 
 #endif