Re: [powerpc] ftrace warning kernel/trace/ftrace.c:2068 with code-patching selftests

From: Steven Rostedt <rostedt@goodmis.org>
To: Yinan Liu <yinan@linux.alibaba.com>
Cc: linuxppc-dev@lists.ozlabs.org, Sachin Sant <sachinp@linux.ibm.com>
Subject: Re: [powerpc] ftrace warning kernel/trace/ftrace.c:2068 with code-patching selftests
Date: Mon, 24 Jan 2022 11:45:48 -0500	[thread overview]
Message-ID: <20220124114548.30241947@gandalf.local.home> (raw)
In-Reply-To: <e9422643-a210-b77f-a037-da63a9d2e925@linux.alibaba.com>

On Mon, 24 Jan 2022 20:15:06 +0800
Yinan Liu <yinan@linux.alibaba.com> wrote:

> Hi, Steven and Sachin
> 
> I don't have a powerpc machine for testing, I guess the ppc has a 
> similar problem with the s390. It's not clear to me why the compiler 
> does this. Maybe we can handle ppc like you did with the s390 before, 
> but I'm not sure if other architectures have similar issues. Or limit 
> BUILDTIME_MCOUNT_SORT to a smaller scope and make it only available for 
> x86 and arm?
> 
> steven, what's your opinion?

Yeah, I think it's time to opt in, instead of opting out.

Something like this:

-- Steve

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c2724d986fa0..5256ebe57451 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -82,6 +82,7 @@ config ARM
 	select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
 	select HAVE_CONTEXT_TRACKING
 	select HAVE_C_RECORDMCOUNT
+	select HAVE_BUILDTIME_MCOUNT_SORT
 	select HAVE_DEBUG_KMEMLEAK if !XIP_KERNEL
 	select HAVE_DMA_CONTIGUOUS if MMU
 	select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c4207cf9bb17..7996548b2b27 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -166,6 +166,7 @@ config ARM64
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_EBPF_JIT
 	select HAVE_C_RECORDMCOUNT
+	select HAVE_BUILDTIME_MCOUNT_SORT
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_CONTEXT_TRACKING
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7399327d1eff..46080dea5dba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -186,6 +186,7 @@ config X86
 	select HAVE_CONTEXT_TRACKING_OFFSTACK	if HAVE_CONTEXT_TRACKING
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_OBJTOOL_MCOUNT		if STACK_VALIDATION
+	select HAVE_BUILDTIME_MCOUNT_SORT
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 752ed89a293b..7e5b92090faa 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -70,10 +70,16 @@ config HAVE_C_RECORDMCOUNT
 	help
 	  C version of recordmcount available?
 
+config HAVE_BUILDTIME_MCOUNT_SORT
+       bool
+       help
+         An architecture selects this if it sorts the mcount_loc section
+	 at build time.
+
 config BUILDTIME_MCOUNT_SORT
        bool
        default y
-       depends on BUILDTIME_TABLE_SORT && !S390
+       depends on HAVE_BUILDTIME_MCOUNT_SORT
        help
          Sort the mcount_loc section at build time.
 
