A question on walking x86 frame stack

[yumin qi]

Hi, Gustavo

  Yes, it displays the nearby stack values around the frame pointer.
  Since FP used by JIT code, it may not be valid stack address. It is
decided by the author to show 5 up/down around FP, 20 up/down around SP (in
case FP not valid), no special meanings I think.

Thanks
Yumin


On Mon, May 21, 2018 at 9:14 AM, Gustavo Romero <gromero at linux.vnet.ibm.com>
wrote:

> Hello,
>
> Does anybody know what's the reason behind the 5 "magic number" being add
> (to FP) and subtracted (from SP) in this SA code for walking the stack
> (lines 523 and 524):
>
> http://hg.openjdk.java.net/jdk/jdk/file/ec881a19d294/src/jdk
> .hotspot.agent/share/classes/sun/jvm/hotspot/runtime/x86/
> X86Frame.java#l523
>
> I think it's just for providing more context / information on the adjacent
> frames but I'm not sure... In that sense I'm wondering if the 5 fields up
> and down the frame have any special meaning or are indeed only other
> adjacent frames.
>
>
> Thanks.
>
> Best regards,
> Gustavo
>
>