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 7ce04771 ("riscv: Workaround mcount
name prior to clang-13").

Link: https://lkml.kernel.org/r/20240125-bump-min-llvm-ver-to-13-0-1-v1-7-f5ff9bda41c5@kernel.orgSigned-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: "Aneesh Kumar K.V (IBM)" <aneesh.kumar@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Conor Dooley <conor@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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)

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)

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") {