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[PowerPC] Save a dword in the powerpc64 signal trampoline

Authored by bdragon on Jan 6 2020, 6:26 PM.



In rS291668, an instruction was added to sigcode64.S without the nop pad at the end being taken out.

Due to alignment, this means that a dword is being wasted on the shared page for no reason.

Take out this nop, and add some comments while I'm here.

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rS FreeBSD src repository
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Event Timeline

bdragon created this revision.Jan 6 2020, 6:26 PM
bdragon added inline comments.Jan 6 2020, 6:29 PM
70 ↗(On Diff #66417)

Actually this comment is incorrect now that I remember what I was thinking at the time regarding it being exec_copyout_strings() that cares.

When I was tracing through this, I was confused about how it worked. Apparently the code in exec_copyout_strings() is only used when a unified shared page is not used.

The rest of the comment should be accurate though.

OK, so my comments are incorrect in general. The nop still needs to go though.

bdragon updated this revision to Diff 66418.Jan 6 2020, 7:19 PM

Remove incorrect comments from original patch, add comment to describe why we're exiting instead.

jhibbits accepted this revision.Jan 14 2020, 9:28 PM
This revision is now accepted and ready to land.Jan 14 2020, 9:28 PM
This revision was automatically updated to reflect the committed changes.