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Date: Thu, 11 Jan 2024 11:19:36 +0200
From: Vladimir Oltean <olteanv@gmail.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
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Subject: Re: [PATCH net-next 08/30] net: dsa: mt7530: change p{5,6}_interface
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On Wed, Jan 10, 2024 at 06:31:11PM +0000, Russell King (Oracle) wrote:
> On Wed, Jan 10, 2024 at 08:05:25PM +0200, Vladimir Oltean wrote:
> > On Wed, Jan 10, 2024 at 08:15:20PM +0300, Arınç ÜNAL wrote:
> > > __builtin_return_address(1) doesn't seem to work. I'm running this on arm64.
> > 
> > I can't tell you why either, I'm sorry. I can just point to the
> > documentation, which does specify that "On some machines it may be
> > impossible to determine the return address of any function other than
> > the current one". If somebody knows what this depends on, feel free to
> > interject.
> > https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html
> > 
> > On my NXP LS1028A (also arm64) plus clang-16 compiler, __builtin_return_address()
> > does work with multiple nesting levels.
> 
> gcc will probably need to be using frame pointers so it can walk the
> stack, if gcc even implements non-zero values to
> __builtin_return_address(). Without frame pointers, it would need an
> unwinder.

Yeah, I guess it's a gcc limitation. I recompiled the kernel for the same
platform with gcc 11.2 from Arm, and I get the same result as Arınç now.