On Thu, Mar 25, 2021 at 3:38 PM Nathan Chancellor <nathan@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx > Link: https://github.com/ClangBuiltLinux/linux/issues/1331 > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Thanks for keeping this alive on clang-10, and resolving it for future releases! Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > 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 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210325223807.2423265-3-nathan%40kernel.org. -- Thanks, ~Nick Desaulniers
