[PATCH] uml: use correct register file size everywhere

This patch uses MAX_REG_NR consistently to refer to the register file size.
 FRAME_SIZE isn't sufficient because on x86_64, it is smaller than the
ptrace register file size.  MAX_REG_NR was introduced as a consistent way
to get the number of registers, but wasn't used everywhere it should be.

When this causes a problem, it makes PTRACE_SETREGS fail on x86_64 because
of a corrupted segment register value in the known-good register file.  The
patch also adds a register dump at that point in case there are any future
problems here.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/include/sysdep-x86_64/ptrace.h

@@ -104,10 +104,6 @@ union uml_pt_regs {
 #endif
 #ifdef UML_CONFIG_MODE_SKAS
 	struct skas_regs {
-		/* x86_64 ptrace uses sizeof(user_regs_struct) as its register
-		 * file size, while i386 uses FRAME_SIZE.  Therefore, we need
-		 * to use UM_FRAME_SIZE here instead of HOST_FRAME_SIZE.
-		 */
 		unsigned long regs[MAX_REG_NR];
 		unsigned long fp[HOST_FP_SIZE];
                 struct faultinfo faultinfo;

arch/um/os-Linux/skas/mem.c

@@ -48,7 +48,7 @@ int multi_op_count = 0;
 static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
 {
 	unsigned long regs[MAX_REG_NR];
-	int n;
+	int n, i;
 	long ret, offset;
 	unsigned long * data;
 	unsigned long * syscall;
@@ -66,9 +66,13 @@ static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
 		 (unsigned long) &__syscall_stub_start);
 
 	n = ptrace_setregs(pid, regs);
-	if(n < 0)
+	if(n < 0){
+		printk("Registers - \n");
+		for(i = 0; i < MAX_REG_NR; i++)
+			printk("\t%d\t0x%lx\n", i, regs[i]);
 		panic("do_syscall_stub : PTRACE_SETREGS failed, errno = %d\n",
-		      n);
+		      -n);
+	}
 
 	wait_stub_done(pid, 0, "do_syscall_stub");
 

arch/um/os-Linux/skas/process.c

@@ -67,7 +67,7 @@ void wait_stub_done(int pid, int sig, char * fname)
 
 	if((n < 0) || !WIFSTOPPED(status) ||
 	   (WSTOPSIG(status) != SIGUSR1 && WSTOPSIG(status) != SIGTRAP)){
-		unsigned long regs[HOST_FRAME_SIZE];
+		unsigned long regs[MAX_REG_NR];
 
 		if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
 			printk("Failed to get registers from stub, "
@@ -76,7 +76,7 @@ void wait_stub_done(int pid, int sig, char * fname)
 			int i;
 
 			printk("Stub registers -\n");
-			for(i = 0; i < HOST_FRAME_SIZE; i++)
+			for(i = 0; i < ARRAY_SIZE(regs); i++)
 				printk("\t%d - %lx\n", i, regs[i]);
 		}
 		panic("%s : failed to wait for SIGUSR1/SIGTRAP, "
@@ -328,7 +328,7 @@ void userspace(union uml_pt_regs *regs)
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
 	int err;
-	unsigned long regs[HOST_FRAME_SIZE];
+	unsigned long regs[MAX_REG_NR];
 	unsigned long fp_regs[HOST_FP_SIZE];
 	unsigned long current_stack = current_stub_stack();
 	struct stub_data *data = (struct stub_data *) current_stack;

arch/um/os-Linux/sys-i386/registers.c

@@ -15,7 +15,7 @@
 
 /* These are set once at boot time and not changed thereafter */
 
-static unsigned long exec_regs[HOST_FRAME_SIZE];
+static unsigned long exec_regs[MAX_REG_NR];
 static unsigned long exec_fp_regs[HOST_FP_SIZE];
 static unsigned long exec_fpx_regs[HOST_XFP_SIZE];
 static int have_fpx_regs = 1;
@@ -101,6 +101,7 @@ void init_registers(int pid)
 {
 	int err;
 
+	memset(exec_regs, 0, sizeof(exec_regs));
 	err = ptrace(PTRACE_GETREGS, pid, 0, exec_regs);
 	if(err)
 		panic("check_ptrace : PTRACE_GETREGS failed, errno = %d",
@@ -124,7 +125,7 @@ void init_registers(int pid)
 
 void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
 {
-	memcpy(regs, exec_regs, HOST_FRAME_SIZE * sizeof(unsigned long));
+	memcpy(regs, exec_regs, sizeof(exec_regs));
 	if(fp_regs != NULL)
 		memcpy(fp_regs, exec_fp_regs,
 		       HOST_FP_SIZE * sizeof(unsigned long));

arch/um/os-Linux/sys-x86_64/registers.c

@@ -14,7 +14,7 @@
 
 /* These are set once at boot time and not changed thereafter */
 
-static unsigned long exec_regs[HOST_FRAME_SIZE];
+static unsigned long exec_regs[MAX_REG_NR];
 static unsigned long exec_fp_regs[HOST_FP_SIZE];
 
 void init_thread_registers(union uml_pt_regs *to)
@@ -72,7 +72,7 @@ void init_registers(int pid)
 
 void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
 {
-	memcpy(regs, exec_regs, HOST_FRAME_SIZE * sizeof(unsigned long));
+	memcpy(regs, exec_regs, sizeof(exec_regs));
 	if(fp_regs != NULL)
 		memcpy(fp_regs, exec_fp_regs,
 		       HOST_FP_SIZE * sizeof(unsigned long));