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riscv: Workaround mcount name prior to clang-13

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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.

Link: https://github.com/ClangBuiltLinux/linux/issues/1331
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
This commit is contained in:
Nathan Chancellor 2021-03-25 15:38:06 -07:00 committed by Palmer Dabbelt
parent 2f095504f4
commit 7ce0477150
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GPG key ID: 2E1319F35FBB1889
3 changed files with 18 additions and 8 deletions
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14
arch/riscv/include/asm/ftrace.h
View file

@ -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)

10
arch/riscv/kernel/mcount.S
View file

@ -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)

2
scripts/recordmcount.pl
View file

@ -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") {