On Wed, Sep 21, 2016 at 11:15:55AM -0700, Leonid Yegoshin wrote:
> On 09/21/2016 06:26 AM, Ralf Baechle wrote:
> > On Thu, Sep 01, 2016 at 05:30:13PM +0100, James Hogan wrote:
> >
> >> Update arch_uprobe_copy_ixol() to use the kmap_atomic() based kernel
> >> address to flush the icache with flush_icache_range(), rather than the
> >> user mapping. We have the kernel mapping available anyway and this
> >> avoids having to switch to using the new __flush_icache_user_range() for
> >> the sake of Enhanced Virtual Addressing (EVA) where flush_icache_range()
> >> will become ineffective on user addresses.
> >>
> >> Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
> >> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> >> Cc: Leonid Yegoshin <leonid.yegoshin@xxxxxxxxxx>
> >> Cc: linux-mips@xxxxxxxxxxxxxx
> >> ---
> >> arch/mips/kernel/uprobes.c | 13 ++++---------
> >> 1 file changed, 4 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/arch/mips/kernel/uprobes.c b/arch/mips/kernel/uprobes.c
> >> index 8452d933a645..9a507ab1ea38 100644
> >> --- a/arch/mips/kernel/uprobes.c
> >> +++ b/arch/mips/kernel/uprobes.c
> >> @@ -301,19 +301,14 @@ int set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> >> void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
> >> void *src, unsigned long len)
> >> {
> >> - void *kaddr;
> >> + void *kaddr, kstart;
> >>
> >> /* Initialize the slot */
> >> kaddr = kmap_atomic(page);
> >> - memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
> >> + kstart = kaddr + (vaddr & ~PAGE_MASK);
> >> + memcpy(kstart, src, len);
> >> + flush_icache_range(kstart, kstart + len);
> >> kunmap_atomic(kaddr);
> >> -
> >> - /*
> >> - * The MIPS version of flush_icache_range will operate safely on
> >> - * user space addresses and more importantly, it doesn't require a
> >> - * VMA argument.
> >> - */
> >> - flush_icache_range(vaddr, vaddr + len);
> > I can't convince myself this is right wrt. to cache aliases ...
> >
> > Ralf
> >
> It is incorrect if there is I-cache aliasing (very rare) and there is no
> HIGHMEM cache aliasing fix (not fixed). But top tree Linux doesn't work
> with I-cache aliasing either.
Well its pretty trivial to just use the newly introduced
__flush_icache_user_range() on the user address instead of using
flush_icache_range().
Cheers
James
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