powerpc: Make single-stepping emulation (mostly) usable on 32-bit

The sc instruction emulation can't be done the same way on 32-bit
as 64-bit yet, but this should work OK.

Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 28 insertions, 1 deletions

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index e79123d1485c..666c2aa55016 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -10,13 +10,18 @@
  */
 #include <linux/kernel.h>
 #include <linux/ptrace.h>
+#include <linux/config.h>
 #include <asm/sstep.h>
 #include <asm/processor.h>
 
 extern char system_call_common[];
 
+#ifdef CONFIG_PPC64
 /* Bits in SRR1 that are copied from MSR */
 #define MSR_MASK        0xffffffff87c0ffff
+#else
+#define MSR_MASK        0x87c0ffff
+#endif
 
 /*
  * Determine whether a conditional branch instruction would branch.
@@ -66,6 +71,7 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
                 if (branch_taken(instr, regs))
                         regs->nip = imm;
                 return 1;
+#ifdef CONFIG_PPC64
         case 17:        /* sc */
                 /*
                  * N.B. this uses knowledge about how the syscall
@@ -79,6 +85,7 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
                 regs->nip = (unsigned long) &system_call_common;
                 regs->msr = MSR_KERNEL;
                 return 1;
+#endif
         case 18:        /* b */
                 imm = instr & 0x03fffffc;
                 if (imm & 0x02000000)
@@ -121,6 +128,15 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
                         if ((regs->msr & MSR_SF) == 0)
                                 regs->nip &= 0xffffffffUL;
                         return 1;
+                case 0x124:     /* mtmsr */
+                        imm = regs->gpr[rd];
+                        if ((imm & MSR_RI) == 0)
+                                /* can't step mtmsr that would clear MSR_RI */
+                                return -1;
+                        regs->msr = imm;
+                        regs->nip += 4;
+                        return 1;
+#ifdef CONFIG_PPC64
                 case 0x164:     /* mtmsrd */
                         /* only MSR_EE and MSR_RI get changed if bit 15 set */
                         /* mtmsrd doesn't change MSR_HV and MSR_ME */
@@ -135,6 +151,7 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
                         if ((imm & MSR_SF) == 0)
                                 regs->nip &= 0xffffffffUL;
                         return 1;
+#endif
                 }
         }
         return 0;
diff --git a/include/asm-powerpc/reg.h b/include/asm-powerpc/reg.h
index 68058d72d8da..bfb45a4523d3 100644
--- a/include/asm-powerpc/reg.h
+++ b/include/asm-powerpc/reg.h
@@ -51,9 +51,17 @@
 #define __MASK(X)       (1UL<<(X))
 #endif
 
+#ifdef CONFIG_PPC64
 #define MSR_SF          __MASK(MSR_SF_LG)       /* Enable 64 bit mode */
 #define MSR_ISF         __MASK(MSR_ISF_LG)      /* Interrupt 64b mode valid on 630 */
 #define MSR_HV          __MASK(MSR_HV_LG)       /* Hypervisor state */
+#else
+/* so tests for these bits fail on 32-bit */
+#define MSR_SF          0
+#define MSR_ISF         0
+#define MSR_HV          0
+#endif
+
 #define MSR_VEC         __MASK(MSR_VEC_LG)      /* Enable AltiVec */
 #define MSR_POW         __MASK(MSR_POW_LG)      /* Enable Power Management */
 #define MSR_WE          __MASK(MSR_WE_LG)       /* Wait State Enable */
diff --git a/include/asm-ppc64/sstep.h b/include/asm-powerpc/sstep.h
index 4a68db50ee6f..630a9889c07c 100644
--- a/include/asm-ppc64/sstep.h
+++ b/include/asm-powerpc/sstep.h
@@ -16,8 +16,10 @@ struct pt_regs;
  * we don't allow putting a breakpoint on an mtmsrd instruction.
  * Similarly we don't allow breakpoints on rfid instructions.
  * These macros tell us if an instruction is a mtmsrd or rfid.
+ * Note that IS_MTMSRD returns true for both an mtmsr (32-bit)
+ * and an mtmsrd (64-bit).
  */
-#define IS_MTMSRD(instr)        (((instr) & 0xfc0007fe) == 0x7c000164)
+#define IS_MTMSRD(instr)        (((instr) & 0xfc0007be) == 0x7c000124)
 #define IS_RFID(instr)          (((instr) & 0xfc0007fe) == 0x4c000024)
 
 /* Emulate instructions that cause a transfer of control. */