m68k: ptrace fixes

This fixes the following issues in ptrace:

- when single stepping into the signal handler stop at the first insn of
  the handler
- handle non-zero stkadj when accessing pc and sr in ptregs
- correctly handle PT_SR in PTRACE_POKEUSR
- report -EIO when trying to read unknown offset in PTRACE_PEEKUSR

Additionally, the handling of the special case that PT_SR accesses a 16
bit word instead of a 32 bit word has been moved into get_reg/put_reg.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

2 files changed, 34 insertions, 17 deletions

diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index c5b33634c980..77fc7c16bf48 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -179,7 +179,11 @@ do_signal_return:
         addql   #8,%sp
         RESTORE_SWITCH_STACK
         addql   #4,%sp
-        jbra    resume_userspace
+        tstl    %d0
+        jeq     resume_userspace
+        | when single stepping into handler stop at the first insn
+        btst    #6,%curptr@(TASK_INFO+TINFO_FLAGS+2)
+        jeq     resume_userspace
 
 do_delayed_trace:
         bclr    #7,%sp@(PT_OFF_SR)      | clear trace bit in SR
diff --git a/arch/m68k/kernel/ptrace.c b/arch/m68k/kernel/ptrace.c
index bd0842059d11..1fc217e5f06b 100644
--- a/arch/m68k/kernel/ptrace.c
+++ b/arch/m68k/kernel/ptrace.c
@@ -46,7 +46,7 @@
 /* Mapping from PT_xxx to the stack offset at which the register is
    saved.  Notice that usp has no stack-slot and needs to be treated
    specially (see get_reg/put_reg below). */
-static int regoff[] = {
+static const int regoff[] = {
         [0]     = PT_REG(d1),
         [1]     = PT_REG(d2),
         [2]     = PT_REG(d3),
@@ -81,6 +81,14 @@ static inline long get_reg(struct task_struct *task, int regno)
                 addr = (unsigned long *)(task->thread.esp0 + regoff[regno]);
         else
                 return 0;
+        /* Need to take stkadj into account. */
+        if (regno == PT_SR || regno == PT_PC) {
+                long stkadj = *(long *)(task->thread.esp0 + PT_REG(stkadj));
+                addr = (unsigned long *) ((unsigned long)addr + stkadj);
+                /* The sr is actually a 16 bit register.  */
+                if (regno == PT_SR)
+                        return *(unsigned short *)addr;
+        }
         return *addr;
 }
 
@@ -98,6 +106,16 @@ static inline int put_reg(struct task_struct *task, int regno,
                 addr = (unsigned long *)(task->thread.esp0 + regoff[regno]);
         else
                 return -1;
+        /* Need to take stkadj into account. */
+        if (regno == PT_SR || regno == PT_PC) {
+                long stkadj = *(long *)(task->thread.esp0 + PT_REG(stkadj));
+                addr = (unsigned long *) ((unsigned long)addr + stkadj);
+                /* The sr is actually a 16 bit register.  */
+                if (regno == PT_SR) {
+                        *(unsigned short *)addr = data;
+                        return 0;
+                }
+        }
         *addr = data;
         return 0;
 }
@@ -107,7 +125,7 @@ static inline int put_reg(struct task_struct *task, int regno,
  */
 static inline void singlestep_disable(struct task_struct *child)
 {
-        unsigned long tmp = get_reg(child, PT_SR) & ~(TRACE_BITS << 16);
+        unsigned long tmp = get_reg(child, PT_SR) & ~TRACE_BITS;
         put_reg(child, PT_SR, tmp);
         clear_tsk_thread_flag(child, TIF_DELAYED_TRACE);
 }
@@ -122,15 +140,15 @@ void ptrace_disable(struct task_struct *child)
 
 void user_enable_single_step(struct task_struct *child)
 {
-        unsigned long tmp = get_reg(child, PT_SR) & ~(TRACE_BITS << 16);
-        put_reg(child, PT_SR, tmp | (T1_BIT << 16));
+        unsigned long tmp = get_reg(child, PT_SR) & ~TRACE_BITS;
+        put_reg(child, PT_SR, tmp | T1_BIT);
         set_tsk_thread_flag(child, TIF_DELAYED_TRACE);
 }
 
 void user_enable_block_step(struct task_struct *child)
 {
-        unsigned long tmp = get_reg(child, PT_SR) & ~(TRACE_BITS << 16);
-        put_reg(child, PT_SR, tmp | (T0_BIT << 16));
+        unsigned long tmp = get_reg(child, PT_SR) & ~TRACE_BITS;
+        put_reg(child, PT_SR, tmp | T0_BIT);
 }
 
 void user_disable_single_step(struct task_struct *child)
@@ -152,8 +170,6 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 
                 if (addr >= 0 && addr < 19) {
                         tmp = get_reg(child, addr);
-                        if (addr == PT_SR)
-                                tmp >>= 16;
                 } else if (addr >= 21 && addr < 49) {
                         tmp = child->thread.fp[addr - 21];
                         /* Convert internal fpu reg representation
@@ -163,7 +179,7 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                                 tmp = ((tmp & 0xffff0000) << 15) |
                                       ((tmp & 0x0000ffff) << 16);
                 } else
-                        break;
+                        goto out_eio;
                 ret = put_user(tmp, (unsigned long *)data);
                 break;
 
@@ -174,9 +190,9 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 
                 if (addr == PT_SR) {
                         data &= SR_MASK;
-                        data <<= 16;
-                        data |= get_reg(child, PT_SR) & ~(SR_MASK << 16);
-                } else if (addr >= 0 && addr < 19) {
+                        data |= get_reg(child, PT_SR) & ~SR_MASK;
+                }
+                if (addr >= 0 && addr < 19) {
                         if (put_reg(child, addr, data))
                                 goto out_eio;
                 } else if (addr >= 21 && addr < 48) {
@@ -196,8 +212,6 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
         case PTRACE_GETREGS:    /* Get all gp regs from the child. */
                 for (i = 0; i < 19; i++) {
                         tmp = get_reg(child, i);
-                        if (i == PT_SR)
-                                tmp >>= 16;
                         ret = put_user(tmp, (unsigned long *)data);
                         if (ret)
                                 break;
@@ -212,8 +226,7 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                                 break;
                         if (i == PT_SR) {
                                 tmp &= SR_MASK;
-                                tmp <<= 16;
-                                tmp |= get_reg(child, PT_SR) & ~(SR_MASK << 16);
+                                tmp |= get_reg(child, PT_SR) & ~SR_MASK;
                         }
                         put_reg(child, i, tmp);
                         data += sizeof(long);