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Subject[PATCH 3/3] riscv: vdso.lds.S: remove hardcoded 0x800 .text start addr
Date
I believe the hardcoded 0x800 and related comments come from the long
history VDSO_TEXT_OFFSET in x86 vdso code, but commit 5b9304933730
("x86 vDSO: generate vdso-syms.lds") and commit f6b46ebf904f ("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>
---
arch/riscv/kernel/vdso/vdso.lds.S | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index 671aa21769bc..cbe2a179331d 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -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);
--
2.40.1
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