From: Arvind Sankar Date: Thu, 9 Jan 2020 15:02:17 +0000 (-0500) Subject: x86/boot/compressed/64: Remove .bss/.pgtable from bzImage X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3ee372ccce4d4e7c610748d0583979d3ed3a0cf4;p=linux.git x86/boot/compressed/64: Remove .bss/.pgtable from bzImage Commit 5b11f1cee579 ("x86, boot: straighten out ranges to copy/zero in compressed/head*.S") introduced a separate .pgtable section, splitting it out from the rest of .bss. This section was added without the writeable flag, marking it as read-only. This results in the linker putting the .rela.dyn section (containing bogus dynamic relocations from head_64.o) after the .bss and .pgtable sections. When objcopy is used to convert compressed/vmlinux into a binary for the bzImage: $ objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux \ arch/x86/boot/vmlinux.bin the .bss and .pgtable sections get materialized as ~176KiB of zero bytes in the binary in order to place .rela.dyn at the correct location. Fix this by marking .pgtable as writeable. This moves the .rela.dyn section up in the ELF image layout so that .bss and .pgtable are the last allocated sections and so don't appear in bzImage. [ bp: Massage commit message. ] Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Acked-by: Kees Cook Link: https://lkml.kernel.org/r/20200109150218.16544-1-nivedita@alum.mit.edu --- diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 68f31c48d6c2b..c8ee6eff13ef0 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -645,7 +645,7 @@ SYM_DATA_END_LABEL(boot_stack, SYM_L_LOCAL, boot_stack_end) /* * Space for page tables (not in .bss so not zeroed) */ - .section ".pgtable","a",@nobits + .section ".pgtable","aw",@nobits .balign 4096 SYM_DATA_LOCAL(pgtable, .fill BOOT_PGT_SIZE, 1, 0)