[PATCH] riscv: Adjust dependencies of HAVE_DYNAMIC_FTRACE selection

From: Nathan Chancellor <nathan@kernel.org>
To: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu
Cc: ndesaulniers@google.com, trix@redhat.com,
	 linux-riscv@lists.infradead.org, llvm@lists.linux.dev,
	 patches@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH] riscv: Adjust dependencies of HAVE_DYNAMIC_FTRACE selection
Date: Tue, 04 Apr 2023 13:34:21 -0700	[thread overview]
Message-ID: <20230404-riscv-dynamic-ftrace-checks-clang-v1-1-0ce296b7d423@kernel.org> (raw)

When building allmodconfig with clang and its integrated assembler and
linking with a version of GNU ld prior to 2.36, the following link error
occurs:

  riscv64-linux-gnu-ld: .init.data has both ordered [`__patchable_function_entries' in init/main.o] and unordered [`.init_array.0' in kernel/trace/trace_benchmark.o] sections
  riscv64-linux-gnu-ld: final link failed: bad value

This is the same error addressed by commit 45bd8951806e ("arm64: Improve
HAVE_DYNAMIC_FTRACE_WITH_REGS selection for clang") for arm64. See that
changelog for a full description of why this error occurs with this
combination of tools.

In a similar manner as that change, restrict the
CONFIG_HAVE_DYNAMIC_FTRACE selection to combinations of tools known to
work so that there are no errors.

Link: https://github.com/ClangBuiltLinux/linux/issues/1817
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/riscv/Kconfig | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index eb7f29a412f8..4b82838ac870 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -136,12 +136,23 @@ config RISCV
 	select TRACE_IRQFLAGS_SUPPORT
 	select UACCESS_MEMCPY if !MMU
 	select ZONE_DMA32 if 64BIT
-	select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8)
+	select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && (CLANG_SUPPORTS_DYNAMIC_FTRACE || GCC_SUPPORTS_DYNAMIC_FTRACE)
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
 
+config CLANG_SUPPORTS_DYNAMIC_FTRACE
+	def_bool CC_IS_CLANG
+	# https://github.com/llvm/llvm-project/commit/6ab8927931851bb42b2c93a00801dc499d7d9b1e
+	depends on CLANG_VERSION >= 130000
+	# https://github.com/ClangBuiltLinux/linux/issues/1817
+	depends on AS_IS_GNU || (AS_IS_LLVM && (LD_IS_LLD || LD_VERSION >= 23600))
+
+config GCC_SUPPORTS_DYNAMIC_FTRACE
+	def_bool CC_IS_GCC
+	depends on $(cc-option,-fpatchable-function-entry=8)
+
 config ARCH_MMAP_RND_BITS_MIN
 	default 18 if 64BIT
 	default 8

---
base-commit: 4622f159098e098611f393cccf73d52b007e70bc
change-id: 20230404-riscv-dynamic-ftrace-checks-clang-6781b41c41ff

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>

