linux-kernel - [PATCH 07/11] riscv: Remove MCOUNT

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Message-Id: <20240125-bump-min-llvm-ver-to-13-0-1-v1-7-f5ff9bda41c5@kernel.org>
Date: Thu, 25 Jan 2024 15:55:13 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: akpm@...ux-foundation.org, masahiroy@...nel.org
Cc: nicolas@...sle.eu, linux-kbuild@...r.kernel.org, llvm@...ts.linux.dev, 
 patches@...ts.linux.dev, linux-kernel@...r.kernel.org, 
 Nathan Chancellor <nathan@...nel.org>, paul.walmsley@...ive.com, 
 palmer@...belt.com, aou@...s.berkeley.edu, conor@...nel.org, 
 linux-riscv@...ts.infradead.org
Subject: [PATCH 07/11] riscv: Remove MCOUNT_NAME workaround

Now that the minimum supported version of LLVM for building the kernel
has been bumped to 13.0.1, the condition for using _mcount as
MCOUNT_NAME is always true, as the build will fail during the
configuration stage for older LLVM versions. Replace MCOUNT_NAME with
_mcount directly.

This effectively reverts commit 7ce047715030 ("riscv: Workaround mcount
name prior to clang-13").

Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
Cc: paul.walmsley@...ive.com
Cc: palmer@...belt.com
Cc: aou@...s.berkeley.edu
Cc: conor@...nel.org
Cc: linux-riscv@...ts.infradead.org
---
 arch/riscv/include/asm/ftrace.h | 14 ++------------
 arch/riscv/kernel/mcount.S      | 10 +++++-----
 scripts/recordmcount.pl         |  2 +-
 3 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 06874fb1311e..cf5b63e789fa 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -13,19 +13,9 @@
 #endif
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
-/*
- * Clang prior to 13 had "mcount" instead of "_mcount":
- * https://github.com/llvm/llvm-project/commit/ef58ae86ba778ed7d01cd3f6bd6d08f943abab44
- */
-#if defined(CONFIG_CC_IS_GCC) || CONFIG_CLANG_VERSION >= 130000
-#define MCOUNT_NAME _mcount
-#else
-#define MCOUNT_NAME mcount
-#endif
-
 #define ARCH_SUPPORTS_FTRACE_OPS 1
 #ifndef __ASSEMBLY__
-void MCOUNT_NAME(void);
+void _mcount(void);
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
 	return addr;
@@ -75,7 +65,7 @@ struct dyn_arch_ftrace {
  * both auipc and jalr at the same time.
  */
 
-#define MCOUNT_ADDR		((unsigned long)MCOUNT_NAME)
+#define MCOUNT_ADDR		((unsigned long)_mcount)
 #define JALR_SIGN_MASK		(0x00000800)
 #define JALR_OFFSET_MASK	(0x00000fff)
 #define AUIPC_OFFSET_MASK	(0xfffff000)
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index d7ec69ac6910..3a42f6287909 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -50,8 +50,8 @@
 
 SYM_TYPED_FUNC_START(ftrace_stub)
 #ifdef CONFIG_DYNAMIC_FTRACE
-       .global MCOUNT_NAME
-       .set    MCOUNT_NAME, ftrace_stub
+       .global _mcount
+       .set    _mcount, ftrace_stub
 #endif
 	ret
 SYM_FUNC_END(ftrace_stub)
@@ -80,7 +80,7 @@ SYM_FUNC_END(return_to_handler)
 #endif
 
 #ifndef CONFIG_DYNAMIC_FTRACE
-SYM_FUNC_START(MCOUNT_NAME)
+SYM_FUNC_START(_mcount)
 	la	t4, ftrace_stub
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	la	t0, ftrace_graph_return
@@ -126,6 +126,6 @@ SYM_FUNC_START(MCOUNT_NAME)
 	jalr	t5
 	RESTORE_ABI_STATE
 	ret
-SYM_FUNC_END(MCOUNT_NAME)
+SYM_FUNC_END(_mcount)
 #endif
-EXPORT_SYMBOL(MCOUNT_NAME)
+EXPORT_SYMBOL(_mcount)
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index f84df9e383fd..0871b2e92584 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -352,7 +352,7 @@ if ($arch eq "x86_64") {
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 } elsif ($arch eq "riscv") {
     $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
-    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL(_PLT)?\\s_?mcount\$";
+    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL(_PLT)?\\s_mcount\$";
     $type = ".quad";
     $alignment = 2;
 } elsif ($arch eq "csky") {

-- 
2.43.0