This series renews one of my last year RFC patch[1], tries to improve
the vdso layout a bit.
patch1 removes useless symbols
patch2 merges .data section of vdso into .rodata because they are
readonly
patch3 is the real renew patch, it removes hardcoded 0x800 .text start
addr. But I rewrite the commit msg per Andrew's suggestions and move
move .note, .eh_frame_hdr, and .eh_frame between .rodata and .text to
keep the actual code well away from the non-instruction data.
Link: https://lore.kernel.org/linux-riscv/[email protected]/ [1]
Jisheng Zhang (3):
riscv: vdso.lds.S: drop __alt_start and __alt_end symbols
riscv: vdso.lds.S: merge .data section into .rodata section
riscv: vdso.lds.S: remove hardcoded 0x800 .text start addr
arch/riscv/kernel/vdso/vdso.lds.S | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
--
2.40.1
The .data section doesn't need to be separate from .rodata section,
they are both readonly.
Signed-off-by: Jisheng Zhang <[email protected]>
Tested-by: Emil Renner Berthing <[email protected]>
---
arch/riscv/kernel/vdso/vdso.lds.S | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index d43fd7c7dd11..671aa21769bc 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -29,7 +29,13 @@ SECTIONS
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
- .rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
+ .rodata : {
+ *(.rodata .rodata.* .gnu.linkonce.r.*)
+ *(.got.plt) *(.got)
+ *(.data .data.* .gnu.linkonce.d.*)
+ *(.dynbss)
+ *(.bss .bss.* .gnu.linkonce.b.*)
+ }
/*
* This linker script is used both with -r and with -shared.
@@ -44,13 +50,6 @@ SECTIONS
.alternative : {
*(.alternative)
}
-
- .data : {
- *(.got.plt) *(.got)
- *(.data .data.* .gnu.linkonce.d.*)
- *(.dynbss)
- *(.bss .bss.* .gnu.linkonce.b.*)
- }
}
/*
--
2.40.1
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 <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Tested-by: Emil Renner Berthing <[email protected]>
---
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
These two symbols are not used, remove them.
Signed-off-by: Jisheng Zhang <[email protected]>
Tested-by: Emil Renner Berthing <[email protected]>
---
arch/riscv/kernel/vdso/vdso.lds.S | 2 --
1 file changed, 2 deletions(-)
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index 82ce64900f3d..d43fd7c7dd11 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -42,9 +42,7 @@ SECTIONS
. = ALIGN(4);
.alternative : {
- __alt_start = .;
*(.alternative)
- __alt_end = .;
}
.data : {
--
2.40.1
Hello:
This series was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[email protected]>:
On Tue, 12 Sep 2023 15:20:12 +0800 you wrote:
> This series renews one of my last year RFC patch[1], tries to improve
> the vdso layout a bit.
>
> patch1 removes useless symbols
> patch2 merges .data section of vdso into .rodata because they are
> readonly
> patch3 is the real renew patch, it removes hardcoded 0x800 .text start
> addr. But I rewrite the commit msg per Andrew's suggestions and move
> move .note, .eh_frame_hdr, and .eh_frame between .rodata and .text to
> keep the actual code well away from the non-instruction data.
>
> [...]
Here is the summary with links:
- [RESEND,1/3] riscv: vdso.lds.S: drop __alt_start and __alt_end symbols
https://git.kernel.org/riscv/c/ddcc7d9bf531
- [RESEND,2/3] riscv: vdso.lds.S: merge .data section into .rodata section
https://git.kernel.org/riscv/c/49cfbdc21faf
- [RESEND,3/3] riscv: vdso.lds.S: remove hardcoded 0x800 .text start addr
https://git.kernel.org/riscv/c/8f8c1ff879fa
You are awesome, thank you!
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