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").

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Nathan Chancellor <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Cc: Albert Ou <[e-mail]>
Cc: "Aneesh Kumar K.V (IBM)" <[e-mail]>
Cc: Ard Biesheuvel <[e-mail]>
Cc: Borislav Petkov (AMD) <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Conor Dooley <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Masahiro Yamada <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: "Naveen N. Rao" <[e-mail]>
Cc: Nicholas Piggin <[e-mail]>
Cc: Nicolas Schier <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/riscv/include/asm/ftrace.h

···
 #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;
···
  * 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

···
 
 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)
···
 #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
···
 	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

···
     $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
 } elsif ($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") {