Commit a1326b17 authored by Mark Rutland's avatar Mark Rutland
Browse files

module/ftrace: handle patchable-function-entry 



When using patchable-function-entry, the compiler will record the
callsites into a section named "__patchable_function_entries" rather
than "__mcount_loc". Let's abstract this difference behind a new
FTRACE_CALLSITE_SECTION, so that architectures don't have to handle this
explicitly (e.g. with custom module linker scripts).

As parisc currently handles this explicitly, it is fixed up accordingly,
with its custom linker script removed. Since FTRACE_CALLSITE_SECTION is
only defined when DYNAMIC_FTRACE is selected, the parisc module loading
code is updated to only use the definition in that case. When
DYNAMIC_FTRACE is not selected, modules shouldn't have this section, so
this removes some redundant work in that case.

To make sure that this is keep up-to-date for modules and the main
kernel, a comment is added to vmlinux.lds.h, with the existing ifdeffery
simplified for legibility.

I built parisc generic-{32,64}bit_defconfig with DYNAMIC_FTRACE enabled,
and verified that the section made it into the .ko files for modules.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarHelge Deller <deller@gmx.de>
Acked-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: default avatarTorsten Duwe <duwe@suse.de>
Tested-by: default avatarAmit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: default avatarSven Schnelle <svens@stackframe.org>
Tested-by: default avatarTorsten Duwe <duwe@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: linux-parisc@vger.kernel.org
parent fbf6c73c

arch/parisc/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -60,7 +60,6 @@ KBUILD_CFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY=1 \ 
		 -DFTRACE_PATCHABLE_FUNCTION_SIZE=$(NOP_COUNT)



CC_FLAGS_FTRACE := -fpatchable-function-entry=$(NOP_COUNT),$(shell echo $$(($(NOP_COUNT)-1)))

KBUILD_LDS_MODULE += $(srctree)/arch/parisc/kernel/module.lds

endif



OBJCOPY_FLAGS =-O binary -R .note -R .comment -S

arch/parisc/kernel/module.c

+7 −3
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <linux/elf.h>

#include <linux/vmalloc.h>

#include <linux/fs.h>

#include <linux/ftrace.h>

#include <linux/string.h>

#include <linux/kernel.h>

#include <linux/bug.h>
@@ -862,7 +863,7 @@ int module_finalize(const Elf_Ehdr *hdr, 
	const char *strtab = NULL;

	const Elf_Shdr *s;

	char *secstrings;

	int err, symindex = -1;

	int symindex = -1;

	Elf_Sym *newptr, *oldptr;

	Elf_Shdr *symhdr = NULL;

#ifdef DEBUG
@@ -946,11 +947,13 @@ int module_finalize(const Elf_Ehdr *hdr, 
			/* patch .altinstructions */

			apply_alternatives(aseg, aseg + s->sh_size, me->name);



#ifdef CONFIG_DYNAMIC_FTRACE

		/* For 32 bit kernels we're compiling modules with

		 * -ffunction-sections so we must relocate the addresses in the

		 *__mcount_loc section.

		 *  ftrace callsite section.

		 */

		if (symindex != -1 && !strcmp(secname, "__mcount_loc")) {

		if (symindex != -1 && !strcmp(secname, FTRACE_CALLSITE_SECTION)) {

			int err;

			if (s->sh_type == SHT_REL)

				err = apply_relocate((Elf_Shdr *)sechdrs,

							strtab, symindex,
@@ -962,6 +965,7 @@ int module_finalize(const Elf_Ehdr *hdr, 
			if (err)

				return err;

		}

#endif

	}

	return 0;

}

arch/parisc/kernel/module.lds

deleted100644 → 0
+0 −7
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



SECTIONS {

	__mcount_loc : {

		*(__patchable_function_entries)

	}

}

include/asm-generic/vmlinux.lds.h

+7 −7
Original line number Diff line number Diff line
@@ -110,17 +110,17 @@ 
#endif



#ifdef CONFIG_FTRACE_MCOUNT_RECORD

#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY

#define MCOUNT_REC()	. = ALIGN(8);				\

			__start_mcount_loc = .;			\

			KEEP(*(__patchable_function_entries))	\

			__stop_mcount_loc = .;

#else

/*

 * The ftrace call sites are logged to a section whose name depends on the

 * compiler option used. A given kernel image will only use one, AKA

 * FTRACE_CALLSITE_SECTION. We capture all of them here to avoid header

 * dependencies for FTRACE_CALLSITE_SECTION's definition.

 */

#define MCOUNT_REC()	. = ALIGN(8);				\

			__start_mcount_loc = .;			\

			KEEP(*(__mcount_loc))			\

			KEEP(*(__patchable_function_entries))	\

			__stop_mcount_loc = .;

#endif

#else

#define MCOUNT_REC()

#endif

include/linux/ftrace.h

+5 −0
Original line number Diff line number Diff line
@@ -738,6 +738,11 @@ static inline unsigned long get_lock_parent_ip(void) 


#ifdef CONFIG_FTRACE_MCOUNT_RECORD

extern void ftrace_init(void);

#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY

#define FTRACE_CALLSITE_SECTION	"__patchable_function_entries"

#else

#define FTRACE_CALLSITE_SECTION	"__mcount_loc"

#endif

#else

static inline void ftrace_init(void) { }

#endif

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