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    Subjectcode sections beyond .text skipped from alternatives_smp_module_add
    In x86-64, I am running into a scenario with certain kernel modules
    where the patching of lock prefix instructions in sections other than
    .text (e.g. .exit.text) is not occurring even though the .smp_locks
    relocations in the .ko file specify instructions in sections other
    than .text for patching. For example (down in the bottom), in
    net/bluetooth/rfcomm.ko, we have a couple of entries in .exit.text for
    patching. However, when I look in the memory page containing the
    .exit.text section in a uni processor system, it doesn't appear the
    lock prefix instructions in .exit.text were patched with NOPs the same
    way other instructions from the .text section in the same page
    underwent patching. This creates a subtle inconsistency where a page
    contains the end of the .text section along with the .exit.text
    section - lock prefixes in instructions from the former section gets
    patched per .smp_locks entries while that doesn't happen for the
    latter within the same page.

    Looking at the code, in module_finalize for x86, only .text seems to
    be getting picked for the patching of lock prefixes while other
    sections such as .exit.text or .init.text are not. Is there a reason
    we skip the other *.text code sections from the lock patches? Would
    making the application of the patching of lock prefixes generic across
    all code sections (rather than just .text) make sense?


    for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
    if (!strcmp(".text", secstrings + s->sh_name))
    text = s;
    if (!strcmp(".smp_locks", secstrings + s->sh_name))
    locks = s;

    if (locks && text) {
    void *lseg = (void *)locks->sh_addr;
    void *tseg = (void *)text->sh_addr;
    alternatives_smp_module_add(me, me->name,
    lseg, lseg + locks->sh_size,
    tseg, tseg + text->sh_size);

    > objdump -r kernel/net/bluetooth/rfcomm/rfcomm.ko

    RELOCATION RECORDS FOR [.smp_locks]:
    0000000000000000 R_X86_64_64 .text+0x00000000000000ac
    0000000000000008 R_X86_64_64 .exit.text+0x0000000000000023
    0000000000000010 R_X86_64_64 .exit.text+0x0000000000000034
    0000000000000018 R_X86_64_64 .text+0x0000000000000619
    0000000000000020 R_X86_64_64 .text+0x000000000000061d

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      Last update: 2011-06-21 10:13    [W:0.021 / U:37.472 seconds]
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