• Lynn Boger's avatar
    runtime: restore r2 when restoring state from gobuf in gogo on ppc64x · 30a63ece
    Lynn Boger authored
    When using plugins with goroutines calling cgo, we hit a case where
    an intermittent SIGSEGV occurs when referencing an address that is based
    on r2 (TOC address). When the failure can be generated in gdb, the
    contents of r2 is wrong even though the value in the current stack's
    slot for r2 is correct. So that means it somehow switched to start
    running the code in this function without passing through the beginning
    of the function which had the correct value of r2 and stored it there.
    
    It was noted that in runtime.gogo when the state is restored from
    gobuf, r2 is not restored from its slot on the stack. Adding the
    instruction to restore r2 prevents the SIGSEGV.
    
    This adds a testcase under testplugin which reproduces the problem if
    the program is run multiple times. The team who reported this problem
    has verified it fixes the issue on their larger, more complex
    application.
    
    Fixes #25756
    
    Change-Id: I6028b6f1f8775d5c23f4ebb57ae273330a28eb8f
    Reviewed-on: https://go-review.googlesource.com/117515
    Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
    Reviewed-by: 's avatarIan Lance Taylor <iant@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    30a63ece
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