8e121b1587
This change adds CFA information to the assembly function 'crosscall1'
and reorgnizes its code to establish well-formed prologue and epilogue.
It will fix an infinite callstack issue when debugging cgo program with
GDB on arm64.
Brief root cause analysis:
GDB's aarch64 unwinder parses prologue to determine current frame's size
and previous PC&SP if CFA information is not available.
The unwinder parses the prologue of 'crosscall1' to determine a frame size
of 0x10, then turns to its next frame trying to compute its previous PC&SP
as they are not saved on current frame's stack as per its 'traditional frame
unwind' rules, which ends up getting an endless frame chain like:
[callee] : pc:<pc0>, sp:<sp0>
crosscall1: pc:<pc1>, sp:<sp0>+0x10
[caller] : pc:<pc1>, sp:<sp0>+0x10+0x10
[caller] : pc:<pc1>, sp:<sp0>+0x10+0x10+0x10
...
GDB fails to detect the 'caller' frame is same as 'crosscall1' and terminate
unwinding since SP increases everytime.
Fixes #37238
Change-Id: Ia6bd8555828541a3a61f7dc9b94dfa00775ec52a
Reviewed-on: https://go-review.googlesource.com/c/go/+/226999
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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