[PATCH] x86: fault_{32|64}.c unify do_page_fault

Harvey Harrison
2008-01-03T01:08:50Z

Begin to unify do_page_fault(), easy code movement first.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
---
Ingo, similar to the kprobes unification patches I did, it gets a bit
uglier before it gets better ;-)

arch/x86/mm/fault_32.c | 38 +++++++++++++++++++++++++++++---------
arch/x86/mm/fault_64.c | 23 ++++++++++++++++++-----
2 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c
index b1893eb..051a4ec 100644
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -375,19 +375,26 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
struct mm_struct *mm;
struct vm_area_struct *vma;
unsigned long address;
- int write, si_code;
- int fault;
+ int write, fault;
+#ifdef CONFIG_x86_64
+ unsigned long flags;
+#endif
+ int si_code;

/*
* We can fault from pretty much anywhere, with unknown IRQ state.
*/
trace_hardirqs_fixup();

- /* get the address */
- address = read_cr2();
-
tsk = current;
+ mm = tsk->mm;

+#ifdef CONFIG_x86_64
+ prefetchw(&mm->mmap_sem);
+#endif
+
+ /* get the address */
+ address = read_cr2();
si_code = SEGV_MAPERR;

/*
@@ -403,9 +410,24 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
* (error_code & 4) == 0, and that the fault was not a
* protection error (error_code & 9) == 0.
*/
+#ifdef CONFIG_X86_32
if (unlikely(address >= TASK_SIZE)) {
- if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
+ if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
+ vmalloc_fault(address) >= 0)
return;
+#else
+ if (unlikely(address >= TASK_SIZE64)) {
+ /*
+ * Don't check for the module range here: its PML4
+ * is always initialized because it's shared with the main
+ * kernel text. Only vmalloc may need PML4 syncups.
+ */
+ if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
+ ((address >= VMALLOC_START && address < VMALLOC_END))) {
+ if (vmalloc_fault(address) >= 0)
+ return;
+ }
+#endif
if (notify_page_fault(regs))
return;
/*
@@ -423,8 +445,6 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
if (regs->flags & (X86_EFLAGS_IF|VM_MASK))
local_irq_enable();

- mm = tsk->mm;
-
/*
* If we're in an interrupt, have no user context or are running in an
* atomic region then we must not take the fault.
@@ -495,7 +515,7 @@ good_area:
goto bad_area;
}

- survive:
+survive:
/*
* If for any reason at all we couldn't handle the fault,
* make sure we exit gracefully rather than endlessly redo
diff --git a/arch/x86/mm/fault_64.c b/arch/x86/mm/fault_64.c
index 357a3e0..97b92b6 100644
--- a/arch/x86/mm/fault_64.c
+++ b/arch/x86/mm/fault_64.c
@@ -426,7 +426,9 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
struct vm_area_struct *vma;
unsigned long address;
int write, fault;
+#ifdef CONFIG_x86_64
unsigned long flags;
+#endif
int si_code;

/*
@@ -436,14 +438,15 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,

tsk = current;
mm = tsk->mm;
+
+#ifdef CONFIG_x86_64
prefetchw(&mm->mmap_sem);
+#endif

/* get the address */
address = read_cr2();
-
si_code = SEGV_MAPERR;

-
/*
* We fault-in kernel-space virtual memory on-demand. The
* 'reference' page table is init_mm.pgd.
@@ -457,6 +460,12 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
* (error_code & 4) == 0, and that the fault was not a
* protection error (error_code & 9) == 0.
*/
+#ifdef CONFIG_X86_32
+ if (unlikely(address >= TASK_SIZE)) {
+ if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
+ vmalloc_fault(address) >= 0)
+ return;
+#else
if (unlikely(address >= TASK_SIZE64)) {
/*
* Don't check for the module range here: its PML4
@@ -468,6 +477,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
if (vmalloc_fault(address) >= 0)
return;
}
+#endif
if (notify_page_fault(regs))
return;
/*
@@ -500,7 +510,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
if (user_mode_vm(regs))
error_code |= PF_USER;

- again:
+again:
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
@@ -531,8 +541,11 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
if (error_code & PF_USER) {
- /* Allow userspace just enough access below the stack pointer
- * to let the 'enter' instruction work.
+ /*
+ * Accessing the stack below %sp is always a bug.
+ * The large cushion allows instructions like enter
+ * and pusha to work. ("enter $65535,$31" pushes
+ * 32 pointers and then decrements %sp by 65535.)
*/
if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp)
goto bad_area;
--
1.5.4.rc2.1097.gb6e0d