x86: remove last user of get_segment_eip

is_prefetch was the last user of get_segment_eip and only on
X86_32.  This function returned the faulting instruction's
address and set the upper segment limit.

Instead, use the convert_ip_to_linear helper and rely on
probe_kernel_address to do the segment checks which was
already done everywhere the segment limit was being checked
on X86_32.

Remove get_segment_eip as well.

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>

4 files changed, 8 insertions, 112 deletions

diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 80b37181a42b..2ef1a5f8d675 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -5,90 +5,6 @@
 #include <linux/mm.h>
 #include <linux/ptrace.h>
 
-#ifdef CONFIG_X86_32
-#include <linux/uaccess.h>
-
-#include <asm/desc.h>
-
-/*
- * 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.
- */
-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
-
-#ifdef CONFIG_X86_32
-static
-#endif
 unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs)
 {
         unsigned long addr, seg;
diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c
index b4d19c2d4f05..36cb67e02b04 100644
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -81,7 +81,6 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
         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. */
@@ -90,30 +89,23 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
         } 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_ip_to_linear(current, regs);
 #endif
 
+        instr = (unsigned char *)convert_ip_to_linear(current, regs);
         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;
 
@@ -155,10 +147,7 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
                 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) &&
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index d519b41f1962..80f8436ac8b2 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -84,7 +84,6 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
         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. */
@@ -93,30 +92,23 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
         } 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_ip_to_linear(current, regs);
 #endif
 
+        instr = (unsigned char *)convert_ip_to_linear(current, regs);
         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;
 
@@ -158,10 +150,7 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
                 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) &&
diff --git a/include/asm-x86/ptrace.h b/include/asm-x86/ptrace.h
index 35c103714906..ee4b595e1ccc 100644
--- a/include/asm-x86/ptrace.h
+++ b/include/asm-x86/ptrace.h
@@ -70,6 +70,10 @@ struct pt_regs {
 #include <asm/segment.h>
 
 struct task_struct;
+
+extern unsigned long
+convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs);
+
 extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code);
 
 /*
@@ -184,8 +188,6 @@ convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs);
 
 #ifdef __KERNEL__
 
-unsigned long get_segment_eip(struct pt_regs *regs, unsigned long *eip_limit);
-
 /*
  * These are defined as per linux/ptrace.h, which see.
  */