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Commit 1867ddb7 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Alistair Strachan
Browse files

FROMLIST: kbuild: fix dynamic ftrace with clang LTO 

With CONFIG_LTO_CLANG enabled, LLVM IR won't be compiled into object
files until modpost_link. This change postpones calls to recordmcount
until after this step.

In order to exclude ftrace_process_locs from inspection, we add a new
code section .text..ftrace, which we tell recordmcount to ignore, and
a __norecordmcount attribute for moving functions to this section.

Bug: 62093296
Bug: 67506682
Change-Id: Iba2c053968206acf533fadab1eb34a743b5088ee
(am from https://patchwork.kernel.org/patch/10060327/

)
Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
parent cee5051d

arch/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -497,7 +497,7 @@ config LTO_NONE 
config LTO_CLANG

	bool "Use clang Link Time Optimization (LTO) (EXPERIMENTAL)"

	depends on ARCH_SUPPORTS_LTO_CLANG

	depends on !FTRACE_MCOUNT_RECORD

	depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT

	depends on CC_IS_CLANG && LD_IS_LLD

	select LTO

	help

include/asm-generic/vmlinux.lds.h

+1 −0
Original line number Diff line number Diff line
@@ -492,6 +492,7 @@ 
		ALIGN_FUNCTION();					\

		*(.text.hot TEXT_MAIN .text.fixup .text.unlikely)	\

		*(.text..refcount)					\

		*(.text..ftrace)					\

		*(.ref.text)						\

	MEM_KEEP(init.text*)						\

	MEM_KEEP(exit.text*)						\

include/linux/compiler-clang.h

+7 −0
Original line number Diff line number Diff line
@@ -43,3 +43,10 @@ 
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))

#define __assume_aligned(a, ...)	\

	__attribute__((__assume_aligned__(a, ## __VA_ARGS__)))



#ifdef CONFIG_LTO_CLANG

#ifdef CONFIG_FTRACE_MCOUNT_RECORD

#define __norecordmcount \

	__attribute__((__section__(".text..ftrace")))

#endif

#endif

include/linux/compiler_types.h

+4 −0
Original line number Diff line number Diff line
@@ -248,6 +248,10 @@ struct ftrace_likely_data { 
# define __gnu_inline

#endif



#ifndef __norecordmcount

#define __norecordmcount

#endif



/*

 * Force always-inline if the user requests it so via the .config.

 * GCC does not warn about unused static inline functions for

kernel/trace/ftrace.c

+3 −3
Original line number Diff line number Diff line
@@ -5500,7 +5500,7 @@ static int ftrace_cmp_ips(const void *a, const void *b) 
	return 0;

}



static int ftrace_process_locs(struct module *mod,

static int __norecordmcount ftrace_process_locs(struct module *mod,

						unsigned long *start,

						unsigned long *end)

{