[Bug runtime/10857] dwarf unwinder doesn't handle call frame instructions taking expressions

[roland at gnu dot org]

------- Additional Comments From roland at gnu dot org  2010-05-07 01:32 -------
If "in the wild" means do they actually appear in real binaries, the answer is
yes.  If you mean "has it hampered some unwinding some systemtap user tried",
then who knows.

pmachata recently did some scripted CFI analysis on a large raft of OS binaries,
which cited the subset of these cases where a recently-fixed gcc bug was
involved.  It would be simpler to script grepping for all DW_CFA_expression,
DW_CFA_def_cfa_expression, and DW_CFA_val_expression uses.

GCC can emit DW_CFA_expression and DW_CFA_def_cfa_expression for x86 and perhaps
other machines.  Without doing the aforementioned grepping, off hand we have
only noticed it being used in x86-32 code generation so far.

glibc uses those in the signal frame on x86_64, and uses DW_CFA_val_expression
in its locking code (used both inside glibc and for libpthread) for x86_64 and i386.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10857

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