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    SubjectRe: [PATCH v5 16/20] scripts/gdb: Add internal helper and convenience function for per-cpu lookup
    On Tue, Jan 29, 2013 at 01:37:59PM +0100, Jan Kiszka wrote:
    > This function allows to obtain a per-cpu variable, either of the current
    > or an explicitly specified CPU.
    >
    > Note: sparc64 version is untested.
    >
    > CC: "David S. Miller" <davem@davemloft.net>
    > CC: sparclinux@vger.kernel.org
    > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
    > ---
    > scripts/gdb/percpu.py | 61 ++++++++++++++++++++++++++++++++++++++++++++
    > scripts/gdb/vmlinux-gdb.py | 1 +
    > 2 files changed, 62 insertions(+), 0 deletions(-)
    > create mode 100644 scripts/gdb/percpu.py
    >
    > diff --git a/scripts/gdb/percpu.py b/scripts/gdb/percpu.py
    > new file mode 100644
    > index 0000000..864962c
    > --- /dev/null
    > +++ b/scripts/gdb/percpu.py
    > @@ -0,0 +1,61 @@
    > +#
    > +# gdb helper commands and functions for Linux kernel debugging
    > +#
    > +# per-cpu tools

    This is actually a very cool thing for CPU guys: it can show what kind
    of hybrid CPUs they've been glueing together, like the following, for
    example:

    ...
    (gdb) p $lx_per_cpu("cpu_info").x86_virt_bits
    $5 = 48 '0'
    (gdb) p $lx_per_cpu("cpu_info").x86_vendor_id
    $6 = "GenuineIntel\000\000\000"
    (gdb) p $lx_per_cpu("cpu_info").x86_model_id
    $7 = "AMD Phenom(tm) 9550 Quad-Core Processor", '\000' <repeats 24 times>
    (gdb)

    Since when does Intel produce CPUs called "AMD Phenom(tm) 9550 Quad-Core
    Processor"? .. hahaha..

    > +#
    > +# Copyright (c) Siemens AG, 2011-2013
    > +#
    > +# Authors:
    > +# Jan Kiszka <jan.kiszka@siemens.com>
    > +#
    > +# This work is licensed under the terms of the GNU GPL version 2.
    > +#
    > +
    > +import gdb
    > +
    > +from utils import *
    > +from task import *
    > +
    > +MAX_CPUS = 4096
    > +
    > +def get_current_cpu():
    > + if get_gdbserver_type() == GDBSERVER_QEMU:
    > + return gdb.selected_thread().num - 1
    > + elif get_gdbserver_type() == GDBSERVER_KGDB:
    > + tid = gdb.selected_thread().ptid[2]
    > + if tid > (0x100000000 - MAX_CPUS - 2):
    > + return 0x100000000 - tid - 2
    > + else:
    > + return get_thread_info(get_task_by_pid(tid))['cpu']
    > + else:
    > + raise gdb.GdbError("Sorry, obtaining the current CPU is "
    > + "not yet supported with this gdb server.")
    > +
    > +def per_cpu(var_ptr, cpu):
    > + if cpu == -1:
    > + cpu = get_current_cpu()
    > + if is_target_arch("sparc:v9"):
    > + offset = gdb.parse_and_eval("trap_block[" + str(cpu) +
    > + "].__per_cpu_base")
    > + else:
    > + offset = gdb.parse_and_eval("__per_cpu_offset[" + str(cpu) +
    > + "]")
    > + pointer = var_ptr.cast(get_long_type()) + offset
    > + return pointer.cast(var_ptr.type).dereference()
    > +
    > +
    > +class PerCpu(gdb.Function):
    > + __doc__ = "Return per-cpu variable.\n" \
    > + "\n" \
    > + "$lx_per_cpu(\"VAR\"[, CPU]): Return the per-cpu variable called VAR for the\n" \
    > + "given CPU number. If CPU is omitted, the CPU of the current context is used.\n" \
    > + "Note that VAR has to be quoted as string."


    Ok, seriously now:

    apropos shows the "Return per-cpu... " line above. Have you found out
    which gdb command shows the rest? help and info both say "Undefined
    command".

    Thanks.

    --
    Regards/Gruss,
    Boris.

    Sent from a fat crate under my desk. Formatting is fine.
    --


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