Unverified Commit 8f8c1ff8 authored Sep 12, 2023 by Jisheng Zhang Committed by Palmer Dabbelt Nov 05, 2023

riscv: vdso.lds.S: remove hardcoded 0x800 .text start addr



I believe the hardcoded 0x800 and related comments come from the long
history VDSO_TEXT_OFFSET in x86 vdso code, but commit 5b930493
("x86 vDSO: generate vdso-syms.lds") and commit f6b46ebf ("x86
vDSO: new layout") removes the comment and hard coding for x86.

Similar as x86 and other arch, riscv doesn't need the rigid layout
using VDSO_TEXT_OFFSET since it "no longer matters to the kernel".
so we could remove the hard coding now, and removing it brings a
small vdso.so and aligns with other architectures.

Also, having enough separation between data and text is important for
I-cache, so similar as x86, move .note, .eh_frame_hdr, and .eh_frame
between .rodata and .text.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20230912072015.2424-4-jszhang@kernel.org


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

parent 49cfbdc2

arch/riscv/kernel/vdso/vdso.lds.S

+8 −9

Original line number	Diff line number	Diff line
		@@ -23,12 +23,8 @@ SECTIONS
		.gnu.version_d : { *(.gnu.version_d) }
		.gnu.version_r : { *(.gnu.version_r) }

		.note : { (.note.) } :text :note
		.dynamic : { *(.dynamic) } :text :dynamic

		.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
		.eh_frame : { KEEP (*(.eh_frame)) } :text

		.rodata : {
		(.rodata .rodata. .gnu.linkonce.r.*)
		(.got.plt) (.got)
		@@ -37,13 +33,16 @@ SECTIONS
		(.bss .bss. .gnu.linkonce.b.*)
		}

		.note : { (.note.) } :text :note

		.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
		.eh_frame : { KEEP (*(.eh_frame)) } :text

		/*
		* This linker script is used both with -r and with -shared.
		* For the layouts to match, we need to skip more than enough
		* space for the dynamic symbol table, etc. If this amount is
		* insufficient, ld -shared will error; simply increase it here.
		* Text is well-separated from actual data: there's plenty of
		* stuff that isn't used at runtime in between.
		*/
		. = 0x800;
		. = ALIGN(16);
		.text : { (.text .text.) } :text

		. = ALIGN(4);