Messages in this thread | | | Subject | Re: [PATCH 02/17] prmem: write rare for static allocation | From | Igor Stoppa <> | Date | Mon, 29 Oct 2018 22:01:22 +0200 |
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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
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