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[83.153.85.71]) by smtp.gmail.com with ESMTPSA id k130sm24234780wmg.6.2016.01.20.01.05.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 20 Jan 2016 01:05:58 -0800 (PST) From: Ard Biesheuvel To: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, keescook@chromium.org, akpm@linux-foundation.org, mingo@kernel.org, hpa@zytor.com, heiko.carstens@de.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, mmarek@suse.cz, rusty@rustcorp.com.au Cc: Ard Biesheuvel Subject: [PATCH 4/4] x86_64: enable text relative kallsyms for 64-bit targets Date: Wed, 20 Jan 2016 10:05:38 +0100 Message-Id: <1453280738-18721-5-git-send-email-ard.biesheuvel@linaro.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1453280738-18721-1-git-send-email-ard.biesheuvel@linaro.org> References: <1453280738-18721-1-git-send-email-ard.biesheuvel@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This enables the newly introduced text-relative kallsyms support when building 64-bit targets. This cuts the size of the kallsyms address table in half, reducing the memory footprint of the kernel .rodata section by about 400 KB for a KALLSYMS_ALL build, and about 100 KB reduction in compressed size. (with CONFIG_RELOCATABLE=y) Signed-off-by: Ard Biesheuvel --- I tested this with my Ubuntu Wily box's config-4.2.0-23-generic, and got the following results: BEFORE: -- 2.5.0 ======= $ size vmlinux text data bss dec hex filename 12972949 2213240 1482752 16668941 fe590d vmlinux $ readelf -S .tmp_kallsyms2.o |less There are 9 section headers, starting at offset 0x3e0788: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align ... [ 4] .rodata PROGBITS 0000000000000000 00000040 00000000001c7738 0000000000000000 A 0 0 8 [ 5] .rela.rodata RELA 0000000000000000 001c7950 0000000000218e38 0000000000000018 I 7 4 8 [ 6] .shstrtab STRTAB 0000000000000000 001c7778 0000000000000039 0000000000000000 0 0 1 $ ls -l arch/x86/boot/bzImage -rw-rw-r-- 1 ard ard 6893168 Jan 20 09:36 arch/x86/boot/bzImage AFTER: ====== $ size vmlinux text data bss dec hex filename 12604501 2213240 1482752 16300493 f8b9cd vmlinux $ readelf -S .tmp_kallsyms2.o |less There are 8 section headers, starting at offset 0x16dd10: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align ... [ 4] .rodata PROGBITS 0000000000000000 00000040 000000000016db20 0000000000000000 A 0 0 8 [ 5] .shstrtab STRTAB 0000000000000000 0016db60 0000000000000034 0000000000000000 0 0 1 ... $ ls -l arch/x86/boot/bzImage -rw-rw-r-- 1 ard ard 6790224 Jan 19 22:24 arch/x86/boot/bzImage --- arch/x86/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4a10ba9e95da..180a94bda8d4 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -142,6 +142,7 @@ config X86 select HAVE_UNSTABLE_SCHED_CLOCK select HAVE_USER_RETURN_NOTIFIER select IRQ_FORCED_THREADING + select KALLSYMS_TEXT_RELATIVE if X86_64 select MODULES_USE_ELF_RELA if X86_64 select MODULES_USE_ELF_REL if X86_32 select OLD_SIGACTION if X86_32