[2/3] riscv: Workaround mcount name prior to clang-13
diff mbox series

Message ID 20210325223807.2423265-3-nathan@kernel.org
State Accepted
Commit 7ce04771503074a7de7f539cc43f5e1b385cb99b
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Series
  • Fix CONFIG_FUNCTION_TRACER with clang
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Commit Message

Nathan Chancellor March 25, 2021, 10:38 p.m. UTC
Prior to clang 13.0.0, the RISC-V name for the mcount symbol was
"mcount", which differs from the GCC version of "_mcount", which results
in the following errors:

riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_level':
main.c:(.text+0xe): undefined reference to `mcount'
riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_start':
main.c:(.text+0x4e): undefined reference to `mcount'
riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_finish':
main.c:(.text+0x92): undefined reference to `mcount'
riscv64-linux-gnu-ld: init/main.o: in function `.LBB32_28':
main.c:(.text+0x30c): undefined reference to `mcount'
riscv64-linux-gnu-ld: init/main.o: in function `free_initmem':
main.c:(.text+0x54c): undefined reference to `mcount'

This has been corrected in https://reviews.llvm.org/D98881 but the
minimum supported clang version is 10.0.1. To avoid build errors and to
gain a working function tracer, adjust the name of the mcount symbol for
older versions of clang in mount.S and recordmcount.pl.

Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1331
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/riscv/include/asm/ftrace.h | 14 ++++++++++++--
 arch/riscv/kernel/mcount.S      | 10 +++++-----
 scripts/recordmcount.pl         |  2 +-
 3 files changed, 18 insertions(+), 8 deletions(-)

Comments

Nick Desaulniers March 29, 2021, 6:32 p.m. UTC | #1
On Thu, Mar 25, 2021 at 3:38 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Prior to clang 13.0.0, the RISC-V name for the mcount symbol was
> "mcount", which differs from the GCC version of "_mcount", which results
> in the following errors:
>
> riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_level':
> main.c:(.text+0xe): undefined reference to `mcount'
> riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_start':
> main.c:(.text+0x4e): undefined reference to `mcount'
> riscv64-linux-gnu-ld: init/main.o: in function `__traceiter_initcall_finish':
> main.c:(.text+0x92): undefined reference to `mcount'
> riscv64-linux-gnu-ld: init/main.o: in function `.LBB32_28':
> main.c:(.text+0x30c): undefined reference to `mcount'
> riscv64-linux-gnu-ld: init/main.o: in function `free_initmem':
> main.c:(.text+0x54c): undefined reference to `mcount'
>
> This has been corrected in https://reviews.llvm.org/D98881 but the
> minimum supported clang version is 10.0.1. To avoid build errors and to
> gain a working function tracer, adjust the name of the mcount symbol for
> older versions of clang in mount.S and recordmcount.pl.
>
> Cc: stable@vger.kernel.org
> Link: https://github.com/ClangBuiltLinux/linux/issues/1331
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks for keeping this alive on clang-10, and resolving it for future releases!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  arch/riscv/include/asm/ftrace.h | 14 ++++++++++++--
>  arch/riscv/kernel/mcount.S      | 10 +++++-----
>  scripts/recordmcount.pl         |  2 +-
>  3 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
> index 845002cc2e57..04dad3380041 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -13,9 +13,19 @@
>  #endif
>  #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
>
> +/*
> + * Clang prior to 13 had "mcount" instead of "_mcount":
> + * https://reviews.llvm.org/D98881
> + */
> +#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(void);
> +void MCOUNT_NAME(void);
>  static inline unsigned long ftrace_call_adjust(unsigned long addr)
>  {
>         return addr;
> @@ -36,7 +46,7 @@ struct dyn_arch_ftrace {
>   * both auipc and jalr at the same time.
>   */
>
> -#define MCOUNT_ADDR            ((unsigned long)_mcount)
> +#define MCOUNT_ADDR            ((unsigned long)MCOUNT_NAME)
>  #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 8a5593ff9ff3..6d462681c9c0 100644
> --- a/arch/riscv/kernel/mcount.S
> +++ b/arch/riscv/kernel/mcount.S
> @@ -47,8 +47,8 @@
>
>  ENTRY(ftrace_stub)
>  #ifdef CONFIG_DYNAMIC_FTRACE
> -       .global _mcount
> -       .set    _mcount, ftrace_stub
> +       .global MCOUNT_NAME
> +       .set    MCOUNT_NAME, ftrace_stub
>  #endif
>         ret
>  ENDPROC(ftrace_stub)
> @@ -78,7 +78,7 @@ ENDPROC(return_to_handler)
>  #endif
>
>  #ifndef CONFIG_DYNAMIC_FTRACE
> -ENTRY(_mcount)
> +ENTRY(MCOUNT_NAME)
>         la      t4, ftrace_stub
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>         la      t0, ftrace_graph_return
> @@ -124,6 +124,6 @@ do_trace:
>         jalr    t5
>         RESTORE_ABI_STATE
>         ret
> -ENDPROC(_mcount)
> +ENDPROC(MCOUNT_NAME)
>  #endif
> -EXPORT_SYMBOL(_mcount)
> +EXPORT_SYMBOL(MCOUNT_NAME)
> diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> index a36df04cfa09..7b83a1aaec98 100755
> --- a/scripts/recordmcount.pl
> +++ b/scripts/recordmcount.pl
> @@ -392,7 +392,7 @@ 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 "nds32") {
> --
> 2.31.0
>
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Patch
diff mbox series

diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 845002cc2e57..04dad3380041 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -13,9 +13,19 @@ 
 #endif
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
+/*
+ * Clang prior to 13 had "mcount" instead of "_mcount":
+ * https://reviews.llvm.org/D98881
+ */
+#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(void);
+void MCOUNT_NAME(void);
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
 	return addr;
@@ -36,7 +46,7 @@  struct dyn_arch_ftrace {
  * both auipc and jalr at the same time.
  */
 
-#define MCOUNT_ADDR		((unsigned long)_mcount)
+#define MCOUNT_ADDR		((unsigned long)MCOUNT_NAME)
 #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 8a5593ff9ff3..6d462681c9c0 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -47,8 +47,8 @@ 
 
 ENTRY(ftrace_stub)
 #ifdef CONFIG_DYNAMIC_FTRACE
-       .global _mcount
-       .set    _mcount, ftrace_stub
+       .global MCOUNT_NAME
+       .set    MCOUNT_NAME, ftrace_stub
 #endif
 	ret
 ENDPROC(ftrace_stub)
@@ -78,7 +78,7 @@  ENDPROC(return_to_handler)
 #endif
 
 #ifndef CONFIG_DYNAMIC_FTRACE
-ENTRY(_mcount)
+ENTRY(MCOUNT_NAME)
 	la	t4, ftrace_stub
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	la	t0, ftrace_graph_return
@@ -124,6 +124,6 @@  do_trace:
 	jalr	t5
 	RESTORE_ABI_STATE
 	ret
-ENDPROC(_mcount)
+ENDPROC(MCOUNT_NAME)
 #endif
-EXPORT_SYMBOL(_mcount)
+EXPORT_SYMBOL(MCOUNT_NAME)
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index a36df04cfa09..7b83a1aaec98 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -392,7 +392,7 @@  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 "nds32") {