From: Paolo 'Blaisorblade' Giarrusso <[email protected]>
This adapts the changes to the i386 handler to the UML one. It isn't enough to
make UML work, however, because UML has some peculiarities. Subsequent patches
fix this.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
linux-2.6.git-paolo/arch/um/kernel/trap_kern.c | 32 +++++++++++++++++++++----
1 files changed, 27 insertions(+), 5 deletions(-)
diff -puN arch/um/kernel/trap_kern.c~rfp-fault-sigsegv-2-uml arch/um/kernel/trap_kern.c
--- linux-2.6.git/arch/um/kernel/trap_kern.c~rfp-fault-sigsegv-2-uml 2005-08-11 23:09:32.000000000 +0200
+++ linux-2.6.git-paolo/arch/um/kernel/trap_kern.c 2005-08-11 23:09:32.000000000 +0200
@@ -37,6 +37,7 @@ int handle_page_fault(unsigned long addr
pmd_t *pmd;
pte_t *pte;
int err = -EFAULT;
+ int access_mask = 0;
*code_out = SEGV_MAPERR;
down_read(&mm->mmap_sem);
@@ -55,14 +56,15 @@ int handle_page_fault(unsigned long addr
good_area:
*code_out = SEGV_ACCERR;
if(is_write && !(vma->vm_flags & VM_WRITE))
- goto out;
+ goto prot_bad;
if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
- goto out;
+ goto prot_bad;
+ access_mask = is_write ? VM_WRITE : 0;
do {
-survive:
- switch (handle_mm_fault(mm, vma, address, is_write)){
+handle_fault:
+ switch (__handle_mm_fault(mm, vma, address, access_mask)) {
case VM_FAULT_MINOR:
current->min_flt++;
break;
@@ -72,6 +74,9 @@ survive:
case VM_FAULT_SIGBUS:
err = -EACCES;
goto out;
+ case VM_FAULT_SIGSEGV:
+ err = -EFAULT;
+ goto out;
case VM_FAULT_OOM:
err = -ENOMEM;
goto out_of_memory;
@@ -87,10 +92,27 @@ survive:
*pte = pte_mkyoung(*pte);
if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
flush_tlb_page(vma, address);
+
+ /* If the PTE is not present, the vma protection are not accurate if
+ * VM_NONUNIFORM; present PTE's are correct for VM_NONUNIFORM and were
+ * already handled otherwise. */
out:
up_read(&mm->mmap_sem);
return(err);
+prot_bad:
+ if (unlikely(vma->vm_flags & VM_NONUNIFORM)) {
+ access_mask = is_write ? VM_WRITE : 0;
+ /* Otherwise, on a legitimate read fault on a page mapped as
+ * exec-only, we get problems. Probably, we should lower
+ * requirements... we should always test just
+ * pte_read/write/exec, on vma->vm_page_prot! This way is
+ * cumbersome. However, for now things should work for UML. */
+ access_mask |= vma->vm_flags & VM_EXEC ? VM_EXEC : VM_READ;
+ goto handle_fault;
+ }
+ goto out;
+
/*
* We ran out of memory, or some other thing happened to us that made
* us unable to handle the page fault gracefully.
@@ -100,7 +122,7 @@ out_of_memory:
up_read(&mm->mmap_sem);
yield();
down_read(&mm->mmap_sem);
- goto survive;
+ goto handle_fault;
}
goto out;
}
_
-
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