Unverified Commit 7ce04771 authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Palmer Dabbelt
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riscv: Workaround mcount name prior to clang-13

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: default avatarNathan Chancellor <nathan@kernel.org>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent 2f095504
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+12 −2
Original line number Diff line number Diff line
@@ -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)
+5 −5
Original line number Diff line number Diff line
@@ -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)
+1 −1
Original line number Diff line number Diff line
@@ -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") {