x86: fix mmiotrace 8-bit register decoding

When SIL, DIL, BPL or SPL registers were used in MMIO, the datum
was extracted from AH, BH, CH, or DH, which are incorrect.

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Cc: "Vegard Nossum" <vegard.nossum@gmail.com>
Cc: "Steven Rostedt" <srostedt@redhat.com>
Cc: proski@gnu.org
Cc: "Pekka Enberg"
	<penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 84 insertions, 37 deletions

diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
index efa1911e20ca..df3d5c861cda 100644
--- a/arch/x86/mm/pf_in.c
+++ b/arch/x86/mm/pf_in.c
@@ -79,25 +79,34 @@ static unsigned int mw32[] = { 0xC7 };
 static unsigned int mw64[] = { 0x89, 0x8B };
 #endif /* not __i386__ */
 
-static int skip_prefix(unsigned char *addr, int *shorted, int *enlarged,
-                                                                int *rexr)
+struct prefix_bits {
+        unsigned shorted:1;
+        unsigned enlarged:1;
+        unsigned rexr:1;
+        unsigned rex:1;
+};
+
+static int skip_prefix(unsigned char *addr, struct prefix_bits *prf)
 {
         int i;
         unsigned char *p = addr;
-        *shorted = 0;
-        *enlarged = 0;
-        *rexr = 0;
+        prf->shorted = 0;
+        prf->enlarged = 0;
+        prf->rexr = 0;
+        prf->rex = 0;
 
 restart:
         for (i = 0; i < ARRAY_SIZE(prefix_codes); i++) {
                 if (*p == prefix_codes[i]) {
                         if (*p == 0x66)
-                                *shorted = 1;
+                                prf->shorted = 1;
 #ifdef __amd64__
                         if ((*p & 0xf8) == 0x48)
-                                *enlarged = 1;
+                                prf->enlarged = 1;
                         if ((*p & 0xf4) == 0x44)
-                                *rexr = 1;
+                                prf->rexr = 1;
+                        if ((*p & 0xf0) == 0x40)
+                                prf->rex = 1;
 #endif
                         p++;
                         goto restart;
@@ -135,12 +144,12 @@ enum reason_type get_ins_type(unsigned long ins_addr)
 {
         unsigned int opcode;
         unsigned char *p;
-        int shorted, enlarged, rexr;
+        struct prefix_bits prf;
         int i;
         enum reason_type rv = OTHERS;
 
         p = (unsigned char *)ins_addr;
-        p += skip_prefix(p, &shorted, &enlarged, &rexr);
+        p += skip_prefix(p, &prf);
         p += get_opcode(p, &opcode);
 
         CHECK_OP_TYPE(opcode, reg_rop, REG_READ);
@@ -156,10 +165,11 @@ static unsigned int get_ins_reg_width(unsigned long ins_addr)
 {
         unsigned int opcode;
         unsigned char *p;
-        int i, shorted, enlarged, rexr;
+        struct prefix_bits prf;
+        int i;
 
         p = (unsigned char *)ins_addr;
-        p += skip_prefix(p, &shorted, &enlarged, &rexr);
+        p += skip_prefix(p, &prf);
         p += get_opcode(p, &opcode);
 
         for (i = 0; i < ARRAY_SIZE(rw8); i++)
@@ -168,7 +178,7 @@ static unsigned int get_ins_reg_width(unsigned long ins_addr)
 
         for (i = 0; i < ARRAY_SIZE(rw32); i++)
                 if (rw32[i] == opcode)
-                        return (shorted ? 2 : (enlarged ? 8 : 4));
+                        return prf.shorted ? 2 : (prf.enlarged ? 8 : 4);
 
         printk(KERN_ERR "mmiotrace: Unknown opcode 0x%02x\n", opcode);
         return 0;
@@ -178,10 +188,11 @@ unsigned int get_ins_mem_width(unsigned long ins_addr)
 {
         unsigned int opcode;
         unsigned char *p;
-        int i, shorted, enlarged, rexr;
+        struct prefix_bits prf;
+        int i;
 
         p = (unsigned char *)ins_addr;
-        p += skip_prefix(p, &shorted, &enlarged, &rexr);
+        p += skip_prefix(p, &prf);
         p += get_opcode(p, &opcode);
 
         for (i = 0; i < ARRAY_SIZE(mw8); i++)
@@ -194,11 +205,11 @@ unsigned int get_ins_mem_width(unsigned long ins_addr)
 
         for (i = 0; i < ARRAY_SIZE(mw32); i++)
                 if (mw32[i] == opcode)
-                        return shorted ? 2 : 4;
+                        return prf.shorted ? 2 : 4;
 
         for (i = 0; i < ARRAY_SIZE(mw64); i++)
                 if (mw64[i] == opcode)
-                        return shorted ? 2 : (enlarged ? 8 : 4);
+                        return prf.shorted ? 2 : (prf.enlarged ? 8 : 4);
 
         printk(KERN_ERR "mmiotrace: Unknown opcode 0x%02x\n", opcode);
         return 0;
@@ -238,7 +249,7 @@ enum {
 #endif
 };
 
-static unsigned char *get_reg_w8(int no, struct pt_regs *regs)
+static unsigned char *get_reg_w8(int no, int rex, struct pt_regs *regs)
 {
         unsigned char *rv = NULL;
 
@@ -255,18 +266,6 @@ static unsigned char *get_reg_w8(int no, struct pt_regs *regs)
         case arg_DL:
                 rv = (unsigned char *)&regs->dx;
                 break;
-        case arg_AH:
-                rv = 1 + (unsigned char *)&regs->ax;
-                break;
-        case arg_BH:
-                rv = 1 + (unsigned char *)&regs->bx;
-                break;
-        case arg_CH:
-                rv = 1 + (unsigned char *)&regs->cx;
-                break;
-        case arg_DH:
-                rv = 1 + (unsigned char *)&regs->dx;
-                break;
 #ifdef __amd64__
         case arg_R8:
                 rv = (unsigned char *)&regs->r8;
@@ -294,9 +293,55 @@ static unsigned char *get_reg_w8(int no, struct pt_regs *regs)
                 break;
 #endif
         default:
-                printk(KERN_ERR "mmiotrace: Error reg no# %d\n", no);
                 break;
         }
+
+        if (rv)
+                return rv;
+
+        if (rex) {
+                /*
+                 * If REX prefix exists, access low bytes of SI etc.
+                 * instead of AH etc.
+                 */
+                switch (no) {
+                case arg_SI:
+                        rv = (unsigned char *)&regs->si;
+                        break;
+                case arg_DI:
+                        rv = (unsigned char *)&regs->di;
+                        break;
+                case arg_BP:
+                        rv = (unsigned char *)&regs->bp;
+                        break;
+                case arg_SP:
+                        rv = (unsigned char *)&regs->sp;
+                        break;
+                default:
+                        break;
+                }
+        } else {
+                switch (no) {
+                case arg_AH:
+                        rv = 1 + (unsigned char *)&regs->ax;
+                        break;
+                case arg_BH:
+                        rv = 1 + (unsigned char *)&regs->bx;
+                        break;
+                case arg_CH:
+                        rv = 1 + (unsigned char *)&regs->cx;
+                        break;
+                case arg_DH:
+                        rv = 1 + (unsigned char *)&regs->dx;
+                        break;
+                default:
+                        break;
+                }
+        }
+
+        if (!rv)
+                printk(KERN_ERR "mmiotrace: Error reg no# %d\n", no);
+
         return rv;
 }
 
@@ -368,11 +413,12 @@ unsigned long get_ins_reg_val(unsigned long ins_addr, struct pt_regs *regs)
         unsigned char mod_rm;
         int reg;
         unsigned char *p;
-        int i, shorted, enlarged, rexr;
+        struct prefix_bits prf;
+        int i;
         unsigned long rv;
 
         p = (unsigned char *)ins_addr;
-        p += skip_prefix(p, &shorted, &enlarged, &rexr);
+        p += skip_prefix(p, &prf);
         p += get_opcode(p, &opcode);
         for (i = 0; i < ARRAY_SIZE(reg_rop); i++)
                 if (reg_rop[i] == opcode) {
@@ -392,10 +438,10 @@ unsigned long get_ins_reg_val(unsigned long ins_addr, struct pt_regs *regs)
 
 do_work:
         mod_rm = *p;
-        reg = ((mod_rm >> 3) & 0x7) | (rexr << 3);
+        reg = ((mod_rm >> 3) & 0x7) | (prf.rexr << 3);
         switch (get_ins_reg_width(ins_addr)) {
         case 1:
-                return *get_reg_w8(reg, regs);
+                return *get_reg_w8(reg, prf.rex, regs);
 
         case 2:
                 return *(unsigned short *)get_reg_w32(reg, regs);
@@ -422,11 +468,12 @@ unsigned long get_ins_imm_val(unsigned long ins_addr)
         unsigned char mod_rm;
         unsigned char mod;
         unsigned char *p;
-        int i, shorted, enlarged, rexr;
+        struct prefix_bits prf;
+        int i;
         unsigned long rv;
 
         p = (unsigned char *)ins_addr;
-        p += skip_prefix(p, &shorted, &enlarged, &rexr);
+        p += skip_prefix(p, &prf);
         p += get_opcode(p, &opcode);
         for (i = 0; i < ARRAY_SIZE(imm_wop); i++)
                 if (imm_wop[i] == opcode) {