Re: [PATCH v3 19/25] powerpc/ftrace: Minimise number of #ifdefs

[Naveen N. Rao]

Christophe Leroy wrote:
> A lot of #ifdefs can be replaced by IS_ENABLED()
>
> Do so.
>
> This requires to have kernel_toc_addr() defined at all time
> as well as PPC_INST_LD_TOC and PPC_INST_STD_LR.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> ---
> v2: Moved the setup of pop outside of the big if()/else() in __ftrace_make_nop()
> ---
>  arch/powerpc/include/asm/code-patching.h |   2 -
>  arch/powerpc/include/asm/module.h        |   2 -
>  arch/powerpc/include/asm/sections.h      |  24 +--
>  arch/powerpc/kernel/trace/ftrace.c       | 182 +++++++++++------------
>  4 files changed, 103 insertions(+), 107 deletions(-)

<snip>

> @@ -710,6 +707,9 @@ void arch_ftrace_update_code(int command)
>
>  #ifdef CONFIG_PPC64
>  #define PACATOC offsetof(struct paca_struct, kernel_toc)
> +#else
> +#define PACATOC 0
> +#endif

This conflicts with my fix for the ftrace init tramp:
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220516071422.463738-1-naveen.n.rao@xxxxxxxxxxxxxxxxxx/

It probably makes sense to retain #ifdef CONFIG_PPC64, so that we can 
get rid of the PACATOC. Here is an incremental diff:

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index da1a2f8ebb72f3..28169a1ccc7377 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -701,11 +701,6 @@ void arch_ftrace_update_code(int command)
}

#ifdef CONFIG_PPC64
-#define PACATOC offsetof(struct paca_struct, kernel_toc)
-#else
-#define PACATOC 0
-#endif
-
extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];

void ftrace_free_init_tramp(void)
@@ -724,7 +719,7 @@ int __init ftrace_dyn_arch_init(void)
	int i;
	unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init };
	u32 stub_insns[] = {
-		PPC_RAW_LD(_R12, _R13, PACATOC),
+		PPC_RAW_LD(_R12, _R13, offsetof(struct paca_struct, kernel_toc)),
		PPC_RAW_ADDIS(_R12, _R12, 0),
		PPC_RAW_ADDI(_R12, _R12, 0),
		PPC_RAW_MTCTR(_R12),
@@ -733,9 +728,6 @@ int __init ftrace_dyn_arch_init(void)
	unsigned long addr;
	long reladdr;

-	if (IS_ENABLED(CONFIG_PPC32))
-		return 0;
-
	addr = ppc_global_function_entry((void *)FTRACE_REGS_ADDR);
	reladdr = addr - kernel_toc_addr();

@@ -754,6 +746,7 @@ int __init ftrace_dyn_arch_init(void)

	return 0;
}
+#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER


- Naveen