• ssanfilippo's avatar
    This commit is the first step towards emitting unwinding information in · 7d073b03
    ssanfilippo authored
    the .eh_frame format as part of the jitdump generated when
    FLAG_perf_prof is enabled. The final goal is allowing precise unwinding
    of callchains that include JITted code when profiling V8 using perf.
    
    Unwinding information is stored in the body of code objects after the
    code itself, prefixed with its length and aligned to a 8-byte boundary.
    A boolean flag in the header signals its presence, resulting in zero
    memory overhead when the generation of unwinding info is disabled or
    no such information was attached to the code object.
    
    A new jitdump record type (with id 4) is introduced for specifying
    optional unwinding information for code load records. The EhFrameHdr
    struct is also introduced, together with a constructor to initialise it
    from the associated code object.
    
    At this stage no unwinding information is written to the jitdump, but
    the infrastructure for doing so is ready in place.
    
    BUG=v8:4899
    LOG=N
    
    Review-Url: https://codereview.chromium.org/1993653003
    Cr-Commit-Position: refs/heads/master@{#37296}
    7d073b03
test-code-layout.cc 2.98 KB