On 10/19/13 12:36, Oleg Nesterov wrote:
On 10/15, David Long wrote:
Allow arches to customize how the instruction is filled into the xol
slot. ARM will use this to insert an undefined instruction after the
real instruction in order to simulate a single step of the instruction
without hardware support.
OK, but
+void __weak arch_uprobe_xol_copy(struct arch_uprobe *auprobe, void *vaddr)
+{
+ memcpy(vaddr, auprobe->insn, MAX_UINSN_BYTES);
+}
+
/*
* xol_get_insn_slot - allocate a slot for xol.
* Returns the allocated slot address or 0.
@@ -1246,6 +1251,7 @@ static unsigned long xol_get_insn_slot(struct uprobe
*uprobe)
{
struct xol_area *area;
unsigned long xol_vaddr;
+ void *kaddr;
area = get_xol_area();
if (!area)
@@ -1256,7 +1262,9 @@ static unsigned long xol_get_insn_slot(struct uprobe
*uprobe)
return 0;
/* Initialize the slot */
- copy_to_page(area->page, xol_vaddr, uprobe->arch.insn, MAX_UINSN_BYTES);
+ kaddr = kmap_atomic(area->page);
+ arch_uprobe_xol_copy(&uprobe->arch, kaddr + (xol_vaddr & ~PAGE_MASK));
+ kunmap_atomic(kaddr);
This looks a bit strange and defeats the purpose of generic helper...
How about
void __weak arch_uprobe_xol_copy(...)
{
copy_to_page(...);
}
then just
- copy_to_page(...);
+ arch_uprobe_xol_copy(...);
?
I was trying to avoid duplicating the VM calls in the
architecture-specific implementations, but maybe that is the cleaner way
to do it after all. I've made changes as suggested above.
Or, I am just curious, can't we have an empty "__weak arch_uprobe_xol_copy" if
we call it right after copy_to_page() ?
Then there would potentially be effectively two copy calls. That
doesn't feel at all the right thing to do.
-dl
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