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Commit 7bd125e5 authored by Sami Tolvanen's avatar Sami Tolvanen
Browse files

FROMLIST: BACKPORT: 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 475bdd7d

arch/Kconfig

+1 −1
Original line number Original line Diff line number Diff line
@@ -503,7 +503,7 @@ config ARCH_SUPPORTS_LTO_CLANG 
config LTO_CLANG

config LTO_CLANG

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

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

	depends on ARCH_SUPPORTS_LTO_CLANG

	depends on ARCH_SUPPORTS_LTO_CLANG

	depends on !FTRACE_MCOUNT_RECORD

	depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT

	select LTO

	select LTO

	select THIN_ARCHIVES

	select THIN_ARCHIVES

	select LD_DEAD_CODE_DATA_ELIMINATION

	select LD_DEAD_CODE_DATA_ELIMINATION

include/asm-generic/vmlinux.lds.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -460,6 +460,7 @@ 
#define TEXT_TEXT							\

#define TEXT_TEXT							\

		ALIGN_FUNCTION();					\

		ALIGN_FUNCTION();					\

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

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

		*(.text..ftrace)					\

		*(.ref.text)						\

		*(.ref.text)						\

	MEM_KEEP(init.text)						\

	MEM_KEEP(init.text)						\

	MEM_KEEP(exit.text)						\

	MEM_KEEP(exit.text)						\

include/linux/compiler-clang.h

+7 −0
Original line number Original line Diff line number Diff line
@@ -15,3 +15,10 @@ 
 * with any version that can compile the kernel

 * with any version that can compile the kernel

 */

 */

#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)

#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)



#ifdef CONFIG_LTO_CLANG

#ifdef CONFIG_FTRACE_MCOUNT_RECORD

#define __norecordmcount \

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

#endif

#endif

include/linux/compiler.h

+4 −0
Original line number Original line Diff line number Diff line
@@ -451,6 +451,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s 
#define __visible

#define __visible

#endif

#endif





#ifndef __norecordmcount

#define __norecordmcount

#endif



/*

/*

 * Assume alignment of return value.

 * Assume alignment of return value.

 */

 */

kernel/trace/ftrace.c

+3 −3
Original line number Original line Diff line number Diff line
@@ -4874,7 +4874,7 @@ static int ftrace_cmp_ips(const void *a, const void *b) 
	return 0;

	return 0;

}

}





static int ftrace_process_locs(struct module *mod,

static int __norecordmcount ftrace_process_locs(struct module *mod,

						unsigned long *start,

						unsigned long *start,

						unsigned long *end)

						unsigned long *end)

{

{