On Tue, 9 Aug 2022 16:24:25 +0530
"Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote:
> Extend commit b39181f7c6907d ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to
> avoid adding weak function") to ppc32 and ppc64 -mprofile-kernel by
> defining FTRACE_MCOUNT_MAX_OFFSET.
>
> For ppc64 -mprofile-kernel ABI, we can have two instructions at function
> entry for TOC setup followed by 'mflr r0' and 'bl _mcount'. So, the
> mcount location is at most the 4th instruction in a function. For ppc32,
> mcount location is always the 3rd instruction in a function, preceded by
> 'mflr r0' and 'stw r0,4(r1)'.
>
> With this patch, and with ppc64le_guest_defconfig and some ftrace/bpf
> config items enabled:
> # grep __ftrace_invalid_address available_filter_functions | wc -l
> 79
I wonder if this patch answers the question to my last email. ;-)
Acked-by: Steven Rostedt (Google) <rost...@goodmis.org>
-- Steve
>
> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/ftrace.h | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h
> b/arch/powerpc/include/asm/ftrace.h
> index 3cee7115441b41..ade406dc6504e3 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -10,6 +10,13 @@
>
> #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
>
> +/* Ignore unused weak functions which will have larger offsets */
> +#ifdef CONFIG_MPROFILE_KERNEL
> +#define FTRACE_MCOUNT_MAX_OFFSET 12
> +#elif defined(CONFIG_PPC32)
> +#define FTRACE_MCOUNT_MAX_OFFSET 8
> +#endif
> +
> #ifndef __ASSEMBLY__
> extern void _mcount(void);
>
>
> base-commit: ff1ed171e05c971652a0ede3d716997de8ee41c9
