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Subject[PATCH] x86: fix mmiotrace 8-bit register decoding
From 8321edde04244cc91470da5a7a71b79b704b0da1 Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@iki.fi>
Date: Mon, 21 Jul 2008 18:49:56 +0300
Subject: [PATCH] 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>
---

This patch was cooked in Linus' tree because I couldn't get
linux-next to boot properly at the time. It applies cleanly to
tip/master though. Another problem I noticed is with non-page-aligned
mappings, but that's a different story.

arch/x86/mm/pf_in.c | 121 +++++++++++++++++++++++++++++++++++----------------
1 files changed, 84 insertions(+), 37 deletions(-)

diff --git a/arch/x86/mm/pf_in.c b/arch/x86/mm/pf_in.c
index efa1911..4d0bf36 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) {
--
1.5.4.5


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