On 26/10/2018 10:41, Peter Zijlstra wrote:
On Wed, Oct 24, 2018 at 12:34:49AM +0300, Igor Stoppa wrote:
+static __always_inline
That's far too large for inline.
The reason for it is that it's supposed to minimize the presence of
gadgets that might be used in JOP attacks.
I am ready to stand corrected, if I'm wrong, but this is the reason why
I did it.
Regarding the function being too large, yes, I would not normally choose
it for inlining.
Actually, I would not normally use "__always_inline" and instead I would
limit myself to plain "inline", at most.
+bool wr_memset(const void *dst, const int c, size_t n_bytes)
+{
+ size_t size;
+ unsigned long flags;
+ uintptr_t d = (uintptr_t)dst;
+
+ if (WARN(!__is_wr_after_init(dst, n_bytes), WR_ERR_RANGE_MSG))
+ return false;
+ while (n_bytes) {
+ struct page *page;
+ uintptr_t base;
+ uintptr_t offset;
+ uintptr_t offset_complement;
+
+ local_irq_save(flags);
+ page = virt_to_page(d);
+ offset = d & ~PAGE_MASK;
+ offset_complement = PAGE_SIZE - offset;
+ size = min(n_bytes, offset_complement);
+ base = (uintptr_t)vmap(&page, 1, VM_MAP, PAGE_KERNEL);
+ if (WARN(!base, WR_ERR_PAGE_MSG)) {
+ local_irq_restore(flags);
+ return false;
+ }
+ memset((void *)(base + offset), c, size);
+ vunmap((void *)base);
BUG
yes, somehow I managed to drop this debug configuration from the debug
builds I made.
[...]
Also, I see an amount of duplication here that shows you're not nearly
lazy enough.
I did notice a certain amount of duplication, but I didn't know how to
exploit it.
--
igor
