powerpc: Use MSR_64BIT in sstep.c, fix kprobes on BOOK3E

We check MSR_SF a lot in sstep.c, to decide if we need to emulate the
truncation of values when running in 32-bit mode. Factor out that code
into a helper, and convert it and the other uses to use MSR_64BIT.

This fixes a bug on BOOK3E where kprobes would end up returning to a
32-bit address, because regs->nip was truncated, because (msr & MSR_SF)
was false.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 27 insertions, 34 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index ae5189ab0049..0e5e540c7778 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -45,6 +45,18 @@ extern int do_stxvd2x(int rn, unsigned long ea);
 #endif
 
 /*
+ * Emulate the truncation of 64 bit values in 32-bit mode.
+ */
+static unsigned long truncate_if_32bit(unsigned long msr, unsigned long val)
+{
+#ifdef __powerpc64__
+        if ((msr & MSR_64BIT) == 0)
+                val &= 0xffffffffUL;
+#endif
+        return val;
+}
+
+/*
  * Determine whether a conditional branch instruction would branch.
  */
 static int __kprobes branch_taken(unsigned int instr, struct pt_regs *regs)
@@ -90,11 +102,8 @@ static unsigned long __kprobes dform_ea(unsigned int instr, struct pt_regs *regs
                 if (instr & 0x04000000)         /* update forms */
                         regs->gpr[ra] = ea;
         }
-#ifdef __powerpc64__
-        if (!(regs->msr & MSR_SF))
-                ea &= 0xffffffffUL;
-#endif
-        return ea;
+
+        return truncate_if_32bit(regs->msr, ea);
 }
 
 #ifdef __powerpc64__
@@ -113,9 +122,8 @@ static unsigned long __kprobes dsform_ea(unsigned int instr, struct pt_regs *reg
                 if ((instr & 3) == 1)           /* update forms */
                         regs->gpr[ra] = ea;
         }
-        if (!(regs->msr & MSR_SF))
-                ea &= 0xffffffffUL;
-        return ea;
+
+        return truncate_if_32bit(regs->msr, ea);
 }
 #endif /* __powerpc64 */
 
@@ -136,11 +144,8 @@ static unsigned long __kprobes xform_ea(unsigned int instr, struct pt_regs *regs
                 if (do_update)          /* update forms */
                         regs->gpr[ra] = ea;
         }
-#ifdef __powerpc64__
-        if (!(regs->msr & MSR_SF))
-                ea &= 0xffffffffUL;
-#endif
-        return ea;
+
+        return truncate_if_32bit(regs->msr, ea);
 }
 
 /*
@@ -466,7 +471,7 @@ static void __kprobes set_cr0(struct pt_regs *regs, int rd)
 
         regs->ccr = (regs->ccr & 0x0fffffff) | ((regs->xer >> 3) & 0x10000000);
 #ifdef __powerpc64__
-        if (!(regs->msr & MSR_SF))
+        if (!(regs->msr & MSR_64BIT))
                 val = (int) val;
 #endif
         if (val < 0)
@@ -487,7 +492,7 @@ static void __kprobes add_with_carry(struct pt_regs *regs, int rd,
                 ++val;
         regs->gpr[rd] = val;
 #ifdef __powerpc64__
-        if (!(regs->msr & MSR_SF)) {
+        if (!(regs->msr & MSR_64BIT)) {
                 val = (unsigned int) val;
                 val1 = (unsigned int) val1;
         }
@@ -570,8 +575,7 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                 if ((instr & 2) == 0)
                         imm += regs->nip;
                 regs->nip += 4;
-                if ((regs->msr & MSR_SF) == 0)
-                        regs->nip &= 0xffffffffUL;
+                regs->nip = truncate_if_32bit(regs->msr, regs->nip);
                 if (instr & 1)
                         regs->link = regs->nip;
                 if (branch_taken(instr, regs))
@@ -604,13 +608,9 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                         imm -= 0x04000000;
                 if ((instr & 2) == 0)
                         imm += regs->nip;
-                if (instr & 1) {
-                        regs->link = regs->nip + 4;
-                        if ((regs->msr & MSR_SF) == 0)
-                                regs->link &= 0xffffffffUL;
-                }
-                if ((regs->msr & MSR_SF) == 0)
-                        imm &= 0xffffffffUL;
+                if (instr & 1)
+                        regs->link = truncate_if_32bit(regs->msr, regs->nip + 4);
+                imm = truncate_if_32bit(regs->msr, imm);
                 regs->nip = imm;
                 return 1;
         case 19:
@@ -618,11 +618,8 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                 case 16:        /* bclr */
                 case 528:       /* bcctr */
                         imm = (instr & 0x400)? regs->ctr: regs->link;
-                        regs->nip += 4;
-                        if ((regs->msr & MSR_SF) == 0) {
-                                regs->nip &= 0xffffffffUL;
-                                imm &= 0xffffffffUL;
-                        }
+                        regs->nip = truncate_if_32bit(regs->msr, regs->nip + 4);
+                        imm = truncate_if_32bit(regs->msr, imm);
                         if (instr & 1)
                                 regs->link = regs->nip;
                         if (branch_taken(instr, regs))
@@ -1616,11 +1613,7 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
                 return 0;       /* invoke DSI if -EFAULT? */
         }
  instr_done:
-        regs->nip += 4;
-#ifdef __powerpc64__
-        if ((regs->msr & MSR_SF) == 0)
-                regs->nip &= 0xffffffffUL;
-#endif
+        regs->nip = truncate_if_32bit(regs->msr, regs->nip + 4);
         return 1;
 
  logical_done: