Re: Re: [PATCH v3 1/7] riscv: ftrace: support fastcc in Clang for WITH_ARGS

[Evgenii Shatokhin]

Hi,

On 03.12.2024 15:05, Björn Töpel wrote:
> Andy Chiu <andybnac@xxxxxxxxx> writes:
>
> > From: Andy Chiu <andy.chiu@xxxxxxxxxx>
> >
> > Some caller-saved registers which are not defined as function arguments
> > in the ABI can still be passed as arguments when the kernel is compiled
> > with Clang. As a result, we must save and restore those registers to
> > prevent ftrace from clobbering them.
> >
> > - [1]: https://reviews.llvm.org/D68559
> >
> > Reported-by: Evgenii Shatokhin <e.shatokhin@xxxxxxxxx>
> > Closes: https://lore.kernel.org/linux-riscv/7e7c7914-445d-426d-89a0-59a9199c45b1@xxxxxxxxx/
> > Acked-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> > Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
>
> Fixes tag?

As far as I understand it, Ftrace for RISC-V has had this problem since 
support for FTRACE_WITH_REGS was added. FTRACE_WITH_ARGS inherited it.

So, it should probably be as follows:

Fixes: aea4c671fb98 ("riscv/ftrace: Add DYNAMIC_FTRACE_WITH_REGS support")

It is more of a workaround rather than a fix though, because it is still 
undecided where the problem is, in the kernel or in LLVM/clang. That 
discussion went nowhere, unfortunately, so it is better to use a 
workaround and move on, IMO.

> Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx>

Regards,
Evgenii