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    SubjectRe: [PATCH 05/10] kbuild: sort the list of symbols exported by the kernel (__ksymtab)
    Andrew Morton wrote:
    > On Tue, 3 Nov 2009 10:06:17 +0000
    > Alan Jenkins <alan-jenkins@tuffmail.co.uk> wrote:
    >
    >
    >> modpost of vmlinux.o now extracts the ksymtab sections and outputs
    >> sorted versions of them as .tmp_exports-asm.S. These sorted sections
    >> are linked into vmlinux and the original unsorted sections are
    >> discarded.
    >>
    >> This will allow modules to be loaded faster, resolving symbols using
    >> binary search, without any increase in the memory needed for the
    >> symbol tables.
    >>
    >> This does not affect the building of modules, so hopefully it won't
    >> affect compile times too much.
    >>
    >> Minimally tested on ARM under QEMU emulator.
    >> Build tested on blackfin; output of "size -A" unchanged.
    >>
    >
    > I'm getting a segfault from write_exports().
    >
    > (gdb) bt
    > #0 0x0000003e5f075510 in strlen () from /lib64/libc.so.6
    > #1 0x0000003e5f045cb8 in vfprintf () from /lib64/libc.so.6
    > #2 0x0000003e5f06683a in vsnprintf () from /lib64/libc.so.6
    > #3 0x0000000000401897 in buf_printf (buf=0x7fff5514f5e0,
    > fmt=0x7fff5514f4e0 "0x%02x ") at scripts/mod/modpost.c:1692
    > #4 0x00000000004042c8 in main (argc=1024, argv=0x7fff5514f5e0)
    > at scripts/mod/modpost.c:2063
    > (gdb) f 4
    > #4 0x00000000004042c8 in main (argc=1024, argv=0x7fff5514f5e0)
    > at scripts/mod/modpost.c:2063
    > 2063 buf_printf(&buf, "__EXPORT_%s_SYMBOL(%s,"
    > (gdb) p sym
    > $1 = (struct symbol *) 0x65c9f0
    > (gdb) p *sym
    > $2 = {next = 0x64c3a0, module = 0x610010, crc = 4077789248, crc_valid = 1,
    > weak = 0, vmlinux = 0, kernel = 0, preloaded = 0, function = 1,
    > export = export_unknown, name = 0x65ca10 "simple_prepare_write"}
    > (gdb) p sym->export
    > $3 = export_unknown
    > (gdb) p/d sym->export
    > $4 = 5
    >
    > but section_names[] (which could be static in write_exports() btw) has
    > only five entries.
    >

    Thanks. I can't work out why this would happen. Could you show the
    options modpost is being run with (make V=1 will do)? Also confirm
    whether this is "MODPOST vmlinux.o" or "MODPOST 1001 modules".


    > main (argc=1024

    It looks like this is the step "MODPOST 1001 modules". But that
    shouldn't run write_exports(). We only run modpost with "-x" for the
    step "MODPOST vmlinux.o". Also, the vmlinux-only modpost is run first,
    so I wonder why it didn't hit the same problem.

    I don't know why sym->vmlinux==0 either; simple_prepare_write() should
    always be built into vmlinux. Perhaps modpost is being run on libfs.o
    for some strange reason.

    Alan


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