[Bug runtime/10821] unwind_frame has an oversized frame

[Bug runtime/10821] unwind_frame has an oversized frame

[wcohen at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10821

William Cohen <wcohen at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |wcohen at redhat dot com

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[Bug runtime/10821] unwind_frame has an oversized frame

[mjw at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10821

Mark Wielaard <mjw at redhat dot com> changed:

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                 CC|                            |mjw at redhat dot com

--- Comment #4 from Mark Wielaard <mjw at redhat dot com> 2010-11-04 19:42:43 UTC ---
(In reply to comment #3)
> It does add a few hundred bytes even for probes points that don't do unwinding,
> and currently only x86 uses the dwarf unwinder.

We discussed on irc, and if we unwind_state in the context data with
 #if defined(STP_USE_DWARF_UNWINDER) && defined(STP_NEED_UNWIND_DATA)
then it should only be included when really needed.

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[Bug runtime/10821] unwind_frame has an oversized frame

[jistone at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10821

Josh Stone <jistone at redhat dot com> changed:

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #5 from Josh Stone <jistone at redhat dot com> 2010-11-06 01:26:47 UTC ---
commit 01a2eba

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[Bug runtime/10821] unwind_frame has an oversized frame

[mjw at redhat dot com]

------- Additional Comments From mjw at redhat dot com  2009-10-28 12:40 -------
One suggestion would be to make unwind_state part of the probe context data
which is staticly allocated. Then we could pass the state from the
[u]context-unwind.stp script-level for use with the unwinder.

It does add a few hundred bytes even for probes points that don't do unwinding,
and currently only x86 uses the dwarf unwinder.

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[Bug runtime/10821] unwind_frame has an oversized frame

[mjw at redhat dot com]

------- Additional Comments From mjw at redhat dot com  2009-10-28 11:57 -------
This comes from the unwind_frame() local struct unwind_state state;
Which is defined in unwind/unwind.h as:

struct unwind_state {
        uleb128_t loc, org;
        const u8 *cieStart, *cieEnd;
        uleb128_t codeAlign;
        sleb128_t dataAlign;
        struct cfa {
                uleb128_t reg, offs;
        } cfa;
        struct unwind_item regs[ARRAY_SIZE(reg_info)];
        unsigned stackDepth:8;
        unsigned version:8;
        const u8 *label;
        const u8 *stack[STP_MAX_STACK_DEPTH];
};

So with struct unwind_item regs[ARRAY_SIZE(reg_info)]; that is pretty big...

It would be nice if we could allocate this per thread/cpu.

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[Bug runtime/10821] unwind_frame has an oversized frame

[jistone at redhat dot com]

------- Additional Comments From jistone at redhat dot com  2009-10-21 16:10 -------
Commit 1d2cd5ff relaxes the -Wframe-larger-than check as a temporary workaround...

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