x86: begin fault_{32|64}.c unification

Move X86_32 only get_segment_eip to X86_64
Move X86_64 only is_errata93 to X86_32

Change X86_32 loop in is_prefetch to highlight the differences
between them.  Fold the logic from __is_prefetch in as well on
X86_32.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 117 insertions, 7 deletions

diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index 7e98a7691283..0d3d5979ce2c 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -64,32 +64,136 @@ static inline int notify_page_fault(struct pt_regs *regs)
 #endif
 }
 
-/* Sometimes the CPU reports invalid exceptions on prefetch.
-   Check that here and ignore.
-   Opcode checker based on code by Richard Brunner */
-static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
-                                unsigned long error_code)
+#ifdef CONFIG_X86_32
+/*
+ * Return EIP plus the CS segment base.  The segment limit is also
+ * adjusted, clamped to the kernel/user address space (whichever is
+ * appropriate), and returned in *eip_limit.
+ *
+ * The segment is checked, because it might have been changed by another
+ * task between the original faulting instruction and here.
+ *
+ * If CS is no longer a valid code segment, or if EIP is beyond the
+ * limit, or if it is a kernel address when CS is not a kernel segment,
+ * then the returned value will be greater than *eip_limit.
+ *
+ * This is slow, but is very rarely executed.
+ */
+static inline unsigned long get_segment_eip(struct pt_regs *regs,
+                                            unsigned long *eip_limit)
+{
+        unsigned long ip = regs->ip;
+        unsigned seg = regs->cs & 0xffff;
+        u32 seg_ar, seg_limit, base, *desc;
+
+        /* Unlikely, but must come before segment checks. */
+        if (unlikely(regs->flags & VM_MASK)) {
+                base = seg << 4;
+                *eip_limit = base + 0xffff;
+                return base + (ip & 0xffff);
+        }
+
+        /* The standard kernel/user address space limit. */
+        *eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg;
+
+        /* By far the most common cases. */
+        if (likely(SEGMENT_IS_FLAT_CODE(seg)))
+                return ip;
+
+        /* Check the segment exists, is within the current LDT/GDT size,
+           that kernel/user (ring 0..3) has the appropriate privilege,
+           that it's a code segment, and get the limit. */
+        __asm__("larl %3,%0; lsll %3,%1"
+                 : "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
+        if ((~seg_ar & 0x9800) || ip > seg_limit) {
+                *eip_limit = 0;
+                return 1;        /* So that returned ip > *eip_limit. */
+        }
+
+        /* Get the GDT/LDT descriptor base.
+           When you look for races in this code remember that
+           LDT and other horrors are only used in user space. */
+        if (seg & (1<<2)) {
+                /* Must lock the LDT while reading it. */
+                mutex_lock(&current->mm->context.lock);
+                desc = current->mm->context.ldt;
+                desc = (void *)desc + (seg & ~7);
+        } else {
+                /* Must disable preemption while reading the GDT. */
+                desc = (u32 *)get_cpu_gdt_table(get_cpu());
+                desc = (void *)desc + (seg & ~7);
+        }
+
+        /* Decode the code segment base from the descriptor */
+        base = get_desc_base((struct desc_struct *)desc);
+
+        if (seg & (1<<2))
+                mutex_unlock(&current->mm->context.lock);
+        else
+                put_cpu();
+
+        /* Adjust EIP and segment limit, and clamp at the kernel limit.
+           It's legitimate for segments to wrap at 0xffffffff. */
+        seg_limit += base;
+        if (seg_limit < *eip_limit && seg_limit >= base)
+                *eip_limit = seg_limit;
+        return ip + base;
+}
+#endif
+
+/*
+ * X86_32
+ * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * X86_64
+ * Sometimes the CPU reports invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * Opcode checker based on code by Richard Brunner
+ */
+static int is_prefetch(struct pt_regs *regs, unsigned long addr,
+                       unsigned long error_code)
 {
         unsigned char *instr;
         int scan_more = 1;
         int prefetch = 0;
         unsigned char *max_instr;
 
+#ifdef CONFIG_X86_32
+        unsigned long limit;
+        if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
+                     boot_cpu_data.x86 >= 6)) {
+                /* Catch an obscure case of prefetch inside an NX page. */
+                if (nx_enabled && (error_code & PF_INSTR))
+                        return 0;
+        } else {
+                return 0;
+        }
+        instr = (unsigned char *)get_segment_eip(regs, &limit);
+#else
         /* If it was a exec fault ignore */
         if (error_code & PF_INSTR)
                 return 0;
-
         instr = (unsigned char __user *)convert_rip_to_linear(current, regs);
+#endif
+
         max_instr = instr + 15;
 
+#ifdef CONFIG_X86_64
         if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
                 return 0;
+#endif
 
         while (scan_more && instr < max_instr) {
                 unsigned char opcode;
                 unsigned char instr_hi;
                 unsigned char instr_lo;
 
+#ifdef CONFIG_X86_32
+                if (instr > (unsigned char *)limit)
+                        break;
+#endif
                 if (probe_kernel_address(instr, opcode))
                         break;
 
@@ -125,12 +229,16 @@ static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
                         scan_more = (instr_lo & 0xC) == 0x4;
                         break;
                 case 0xF0:
-                        /* 0xF0, 0xF2, and 0xF3 are valid prefixes in all modes. */
+                        /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
                         scan_more = !instr_lo || (instr_lo>>1) == 1;
                         break;
                 case 0x00:
                         /* Prefetch instruction is 0x0F0D or 0x0F18 */
                         scan_more = 0;
+#ifdef CONFIG_X86_32
+                        if (instr > (unsigned char *)limit)
+                                break;
+#endif
                         if (probe_kernel_address(instr, opcode))
                                 break;
                         prefetch = (instr_lo == 0xF) &&
@@ -185,6 +293,7 @@ bad:
         printk("BAD\n");
 }
 
+#ifdef CONFIG_X86_64
 static const char errata93_warning[] =
 KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
 KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n"
@@ -218,6 +327,7 @@ static int is_errata93(struct pt_regs *regs, unsigned long address)
         }
         return 0;
 }
+#endif
 
 static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
                                  unsigned long error_code)