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    SubjectRe: [PATCH -tip 5/4] Expands irq-off region in text_poke()
    Mathieu Desnoyers wrote:
    >>> I think irq off should cover the BUG_ON too. This safety check assumes
    >>> we are the only ones modifying "addr".
    >> I think others don't change without text_mutex, don't it?
    >>
    >
    > They shouldn't, but given we decided to grow the irq off region to
    > contain all the code that needs to be executed atomically, it should
    > also contain the BUG_ON, because it is expected to be as atomic as the
    > rest of the code.

    Hm, sure, I updated the delta patch.

    Expand irq-off region to cover fixmap using code and cache synchronizing.

    Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    Cc: Ingo Molnar <mingo@elte.hu>
    ---
    arch/x86/kernel/alternative.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    Index: linux-2.6-tip/arch/x86/kernel/alternative.c
    ===================================================================
    --- linux-2.6-tip.orig/arch/x86/kernel/alternative.c
    +++ linux-2.6-tip/arch/x86/kernel/alternative.c
    @@ -526,13 +526,12 @@ void *__kprobes text_poke(void *addr, co
    pages[1] = virt_to_page(addr + PAGE_SIZE);
    }
    BUG_ON(!pages[0]);
    + local_irq_save(flags);
    set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
    if (pages[1])
    set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
    vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
    - local_irq_save(flags);
    memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
    - local_irq_restore(flags);
    clear_fixmap(FIX_TEXT_POKE0);
    if (pages[1])
    clear_fixmap(FIX_TEXT_POKE1);
    @@ -542,5 +541,6 @@ void *__kprobes text_poke(void *addr, co
    that causes hangs on some VIA CPUs. */
    for (i = 0; i < len; i++)
    BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
    + local_irq_restore(flags);
    return addr;
    }
    --
    Masami Hiramatsu

    Software Engineer
    Hitachi Computer Products (America) Inc.
    Software Solutions Division

    e-mail: mhiramat@redhat.com



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