From 0fddb79bf283a561eb81f09d01f5ac8f61bf8966 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Tue, 2 May 2023 07:41:05 +0000 Subject: arm64: lds: move .got section out of .text Currently, the .got section is placed within the output section .text. However, when .got is non-empty, the SHF_WRITE flag is set for .text when linked by lld. GNU ld recognizes .text as a special section and ignores the SHF_WRITE flag. By renaming .text, we can also get the SHF_WRITE flag. The kernel has performed R_AARCH64_RELATIVE resolving very early, and can then assume that .got is read-only. Let's move .got to the vmlinux_rodata pseudo-segment. As Ard Biesheuvel notes: "This matters to consumers of the vmlinux ELF representation of the kernel image, such as syzkaller, which disregards writable PT_LOAD segments when resolving code symbols. The kernel itself does not care about this distinction, but given that the GOT contains data and not code, it does not require executable permissions, and therefore does not belong in .text to begin with." Reviewed-by: Ard Biesheuvel Signed-off-by: Fangrui Song Link: https://lore.kernel.org/r/20230502074105.1541926-1-maskray@google.com Signed-off-by: Will Deacon --- arch/arm64/kernel/vmlinux.lds.S | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) (limited to 'arch') diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index b9202c2ee18e..3cd7e76cc562 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -181,18 +181,8 @@ SECTIONS KPROBES_TEXT HYPERVISOR_TEXT *(.gnu.warning) - . = ALIGN(16); - *(.got) /* Global offset table */ } - /* - * Make sure that the .got.plt is either completely empty or it - * contains only the lazy dispatch entries. - */ - .got.plt : { *(.got.plt) } - ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, - "Unexpected GOT/PLT entries detected!") - . = ALIGN(SEGMENT_ALIGN); _etext = .; /* End of text section */ @@ -201,6 +191,15 @@ SECTIONS HYPERVISOR_DATA_SECTIONS + .got : { *(.got) } + /* + * Make sure that the .got.plt is either completely empty or it + * contains only the lazy dispatch entries. + */ + .got.plt : { *(.got.plt) } + ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, + "Unexpected GOT/PLT entries detected!") + /* code sections that are never executed via the kernel mapping */ .rodata.text : { TRAMP_TEXT -- cgit v1.2.3