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x86: move get_segment_eip() to step.c
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get_segment_eip has similarities to convert_rip_to_linear(),
and is used in a similar context.  Move get_segment_eip to
step.c to allow easier consolidation.

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>
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Harvey Harrison authored and Ingo Molnar committed Jan 30, 2008
1 parent 3d97775 commit 1379a5c
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Showing 4 changed files with 83 additions and 154 deletions.
81 changes: 81 additions & 0 deletions arch/x86/kernel/step.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,87 @@
#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
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77 changes: 0 additions & 77 deletions arch/x86/mm/fault_32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -61,83 +61,6 @@ static inline int notify_page_fault(struct pt_regs *regs)
#endif
}

#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.
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77 changes: 0 additions & 77 deletions arch/x86/mm/fault_64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,83 +64,6 @@ static inline int notify_page_fault(struct pt_regs *regs)
#endif
}

#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.
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2 changes: 2 additions & 0 deletions include/asm-x86/ptrace.h
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,8 @@ convert_rip_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.
*/
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