From mboxrd@z Thu Jan 1 00:00:00 1970 From: js@sig21.net (Johannes Stezenbach) Date: Fri, 4 Jun 2010 12:38:51 +0200 Subject: [PATCH RFC] fix placement of the .note.gnu.build-id section Message-ID: <20100604103851.GA5616@sig21.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, I've brought up the issue before but there was no conclusion: http://lists.infradead.org/pipermail/linux-arm-kernel/2010-May/015994.html Now there was a thread on lkml that brought to my attention that perf uses the build-id to match perf record files to the matching vmlinux ELF file: http://lkml.org/lkml/2010/6/3/445 I'm not sure about the state of perf on ARM, but I guess we should follow x86, thus I'm proposing the following patch. ------------- ARM: fix placement of the .note.gnu.build-id section The build-id and other ELF notes should be made available at runtime in /sys/kernel/notes because it is used by perf to match record files to the vmlinux ELF file. Correcting the placement of the build-id section in the vmlinux ELF file also avoids problems for JTAG debuggers which cannot load the ELF file with the misplaced section into target RAM. Old layout: Program Header: LOAD off 0x00008000 vaddr 0x00000000 paddr 0x00000000 align 2**15 filesz 0x00000024 memsz 0x00000024 flags r-- LOAD off 0x00010000 vaddr 0xc0008000 paddr 0xc0008000 align 2**15 filesz 0x0033cb60 memsz 0x0036df04 flags rwx NOTE off 0x00008000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000024 memsz 0x00000024 flags r-- Sections: Idx Name Size VMA LMA File off Algn 0 .note.gnu.build-id 00000024 00000000 00000000 00008000 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA, LINK_ONCE_DISCARD New layout: Program Header: LOAD off 0x00008000 vaddr 0xc0008000 paddr 0xc0008000 align 2**15 filesz 0x0031b024 memsz 0x0031b024 flags r-x LOAD off 0x00324000 vaddr 0xc0324000 paddr 0xc0324000 align 2**15 filesz 0x00020b60 memsz 0x00051f04 flags rwx NOTE off 0x00323000 vaddr 0xc0323000 paddr 0xc0323000 align 2**2 filesz 0x00000024 memsz 0x00000024 flags --- Sections: Idx Name Size VMA LMA File off Algn 7 .notes 00000024 c0323000 c0323000 00323000 2**2 CONTENTS, ALLOC, LOAD, READONLY, DATA, LINK_ONCE_DISCARD Signed-off-by: Johannes Stezenbach diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 64ba313..f938736 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -15,7 +15,7 @@ ifeq ($(CONFIG_CPU_ENDIAN_BE8),y) LDFLAGS_vmlinux += --be8 endif -OBJCOPYFLAGS :=-O binary -R .note -R .note.gnu.build-id -R .comment -S +OBJCOPYFLAGS :=-O binary -R .comment -S GZFLAGS :=-9 #KBUILD_CFLAGS +=-pipe # Explicitly specifiy 32-bit ARM ISA since toolchain default can be -mthumb: diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index b16c079..2fca978 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -17,6 +17,12 @@ jiffies = jiffies_64; jiffies = jiffies_64 + 4; #endif +PHDRS { + text PT_LOAD FLAGS(5); /* R_E */ + data PT_LOAD FLAGS(7); /* RWE */ + note PT_NOTE FLAGS(0); /* ___ */ +} + SECTIONS { #ifdef CONFIG_XIP_KERNEL @@ -52,7 +58,7 @@ SECTIONS __init_begin = _stext; INIT_DATA #endif - } + } :text PERCPU(PAGE_SIZE) @@ -104,6 +110,8 @@ SECTIONS RO_DATA(PAGE_SIZE) + NOTES :text :note + _etext = .; /* End of text and rodata section */ #ifdef CONFIG_ARM_UNWIND @@ -115,7 +123,7 @@ SECTIONS __start_unwind_idx = .; *(.ARM.exidx*) __stop_unwind_idx = .; - } + } :text .ARM.unwind_tab : { __start_unwind_tab = .; *(.ARM.extab*) @@ -169,7 +177,7 @@ SECTIONS CONSTRUCTORS _edata = .; - } + } :data _edata_loc = __data_loc + SIZEOF(.data); #ifdef CONFIG_HAVE_TCM