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x86: cosmetic fixes fault_{32|64}.c
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First step towards unifying these files.
- Checkpatch trailing whitespace fixes
- Checkpatch indentation of switch statement fixes
- Checkpatch single statement ifs need no braces fixes
- Checkpatch consistent spacing after comma fixes
- Introduce defines for pagefault error bits from X86_64 and add useful
  comment from X86_32.  Use these defines in X86_32 where obvious.
- Unify comments between 32|64 bit
- Small ifdef movement for CONFIG_KPROBES in notify_page_fault()
- Introduce X86_64 only case statement

No Functional Changes.

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 1d16b53 commit 33cb524
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Showing 2 changed files with 160 additions and 139 deletions.
148 changes: 83 additions & 65 deletions arch/x86/mm/fault_32.c
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Original file line number Diff line number Diff line change
@@ -1,6 +1,4 @@
/*
* linux/arch/i386/mm/fault.c
*
* Copyright (C) 1995 Linus Torvalds
*/

Expand Down Expand Up @@ -30,11 +28,25 @@
#include <asm/desc.h>
#include <asm/segment.h>

extern void die(const char *,struct pt_regs *,long);
/*
* Page fault error code bits
* bit 0 == 0 means no page found, 1 means protection fault
* bit 1 == 0 means read, 1 means write
* bit 2 == 0 means kernel, 1 means user-mode
* bit 3 == 1 means use of reserved bit detected
* bit 4 == 1 means fault was an instruction fetch
*/
#define PF_PROT (1<<0)
#define PF_WRITE (1<<1)
#define PF_USER (1<<2)
#define PF_RSVD (1<<3)
#define PF_INSTR (1<<4)

extern void die(const char *, struct pt_regs *, long);

#ifdef CONFIG_KPROBES
static inline int notify_page_fault(struct pt_regs *regs)
{
#ifdef CONFIG_KPROBES
int ret = 0;

/* kprobe_running() needs smp_processor_id() */
Expand All @@ -46,13 +58,10 @@ static inline int notify_page_fault(struct pt_regs *regs)
}

return ret;
}
#else
static inline int notify_page_fault(struct pt_regs *regs)
{
return 0;
}
#endif
}

/*
* Return EIP plus the CS segment base. The segment limit is also
Expand All @@ -65,7 +74,7 @@ static inline int notify_page_fault(struct pt_regs *regs)
* 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,
Expand All @@ -84,7 +93,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,

/* 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;
Expand All @@ -99,7 +108,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
return 1; /* So that returned ip > *eip_limit. */
}

/* Get the GDT/LDT descriptor base.
/* 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)) {
Expand All @@ -109,16 +118,16 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
desc = (void *)desc + (seg & ~7);
} else {
/* Must disable preemption while reading the GDT. */
desc = (u32 *)get_cpu_gdt_table(get_cpu());
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)) {
if (seg & (1<<2))
mutex_unlock(&current->mm->context.lock);
} else
else
put_cpu();

/* Adjust EIP and segment limit, and clamp at the kernel limit.
Expand All @@ -129,47 +138,63 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
return ip + base;
}

/*
/*
* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
* Check that here and ignore it.
*/
static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
{
{
unsigned long limit;
unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit);
unsigned char *instr = (unsigned char *)get_segment_eip(regs, &limit);
int scan_more = 1;
int prefetch = 0;
int prefetch = 0;
int i;

for (i = 0; scan_more && i < 15; i++) {
for (i = 0; scan_more && i < 15; i++) {
unsigned char opcode;
unsigned char instr_hi;
unsigned char instr_lo;

if (instr > (unsigned char *)limit)
break;
if (probe_kernel_address(instr, opcode))
break;
break;

instr_hi = opcode & 0xf0;
instr_lo = opcode & 0x0f;
instr_hi = opcode & 0xf0;
instr_lo = opcode & 0x0f;
instr++;

switch (instr_hi) {
switch (instr_hi) {
case 0x20:
case 0x30:
/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
/*
* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
* In X86_64 long mode, the CPU will signal invalid
* opcode if some of these prefixes are present so
* X86_64 will never get here anyway
*/
scan_more = ((instr_lo & 7) == 0x6);
break;

#ifdef CONFIG_X86_64
case 0x40:
/*
* In AMD64 long mode 0x40..0x4F are valid REX prefixes
* Need to figure out under what instruction mode the
* instruction was issued. Could check the LDT for lm,
* but for now it's good enough to assume that long
* mode only uses well known segments or kernel.
*/
scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
break;
#endif
case 0x60:
/* 0x64 thru 0x67 are valid prefixes in all modes. */
scan_more = (instr_lo & 0xC) == 0x4;
break;
break;
case 0xF0:
/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
scan_more = !instr_lo || (instr_lo>>1) == 1;
break;
break;
case 0x00:
/* Prefetch instruction is 0x0F0D or 0x0F18 */
scan_more = 0;
Expand All @@ -179,11 +204,11 @@ static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
break;
prefetch = (instr_lo == 0xF) &&
(opcode == 0x0D || opcode == 0x18);
break;
break;
default:
scan_more = 0;
break;
}
}
}
return prefetch;
}
Expand All @@ -199,7 +224,7 @@ static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
return __is_prefetch(regs, addr);
}
return 0;
}
}

static noinline void force_sig_info_fault(int si_signo, int si_code,
unsigned long address, struct task_struct *tsk)
Expand Down Expand Up @@ -284,19 +309,12 @@ int show_unhandled_signals = 1;
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
*
* error_code:
* bit 0 == 0 means no page found, 1 means protection fault
* bit 1 == 0 means read, 1 means write
* bit 2 == 0 means kernel, 1 means user-mode
* bit 3 == 1 means use of reserved bit detected
* bit 4 == 1 means fault was an instruction fetch
*/
void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct * vma;
struct vm_area_struct *vma;
unsigned long address;
int write, si_code;
int fault;
Expand All @@ -307,7 +325,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
trace_hardirqs_fixup();

/* get the address */
address = read_cr2();
address = read_cr2();

tsk = current;

Expand Down Expand Up @@ -350,7 +368,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)

/*
* If we're in an interrupt, have no user context or are running in an
* atomic region then we must not take the fault..
* atomic region then we must not take the fault.
*/
if (in_atomic() || !mm)
goto bad_area_nosemaphore;
Expand All @@ -371,7 +389,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
* thus avoiding the deadlock.
*/
if (!down_read_trylock(&mm->mmap_sem)) {
if ((error_code & 4) == 0 &&
if ((error_code & PF_USER) == 0 &&
!search_exception_tables(regs->ip))
goto bad_area_nosemaphore;
down_read(&mm->mmap_sem);
Expand All @@ -384,7 +402,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
if (error_code & 4) {
if (error_code & PF_USER) {
/*
* Accessing the stack below %sp is always a bug.
* The large cushion allows instructions like enter
Expand All @@ -403,19 +421,19 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
good_area:
si_code = SEGV_ACCERR;
write = 0;
switch (error_code & 3) {
default: /* 3: write, present */
/* fall through */
case 2: /* write, not present */
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
write++;
break;
case 1: /* read, present */
switch (error_code & (PF_PROT|PF_WRITE)) {
default: /* 3: write, present */
/* fall through */
case PF_WRITE: /* write, not present */
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
write++;
break;
case PF_PROT: /* read, present */
goto bad_area;
case 0: /* read, not present */
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
case 0: /* read, not present */
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
}

survive:
Expand Down Expand Up @@ -457,14 +475,14 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)

bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */
if (error_code & 4) {
if (error_code & PF_USER) {
/*
* It's possible to have interrupts off here.
*/
local_irq_enable();

/*
* Valid to do another page fault here because this one came
/*
* Valid to do another page fault here because this one came
* from user space.
*/
if (is_prefetch(regs, address, error_code))
Expand Down Expand Up @@ -492,7 +510,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
*/
if (boot_cpu_data.f00f_bug) {
unsigned long nr;

nr = (address - idt_descr.address) >> 3;

if (nr == 6) {
Expand All @@ -507,13 +525,13 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
if (fixup_exception(regs))
return;

/*
/*
* Valid to do another page fault here, because if this fault
* had been triggered by is_prefetch fixup_exception would have
* had been triggered by is_prefetch fixup_exception would have
* handled it.
*/
if (is_prefetch(regs, address, error_code))
return;
if (is_prefetch(regs, address, error_code))
return;

/*
* Oops. The kernel tried to access some bad page. We'll have to
Expand Down Expand Up @@ -541,7 +559,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
else
printk(KERN_ALERT "BUG: unable to handle kernel paging"
" request");
printk(" at virtual address %08lx\n",address);
printk(" at virtual address %08lx\n", address);
printk(KERN_ALERT "printing ip: %08lx ", regs->ip);

page = read_cr3();
Expand Down Expand Up @@ -605,7 +623,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
up_read(&mm->mmap_sem);

/* Kernel mode? Handle exceptions or die */
if (!(error_code & 4))
if (!(error_code & PF_USER))
goto no_context;

/* User space => ok to do another page fault */
Expand Down
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