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Subject[PATCH] x86_64 vDSO linker script cleanup
Date
This replaces my earlier patch by the same title:
x86_64-vdso-linker-script-cleanup.patch


Thanks,
Roland

---

[PATCH] x86_64 vDSO linker script cleanup

This reorganizes the x86_64 vDSO layout to pack the contents better.
This yields a smaller image, while keeping code cache-aligned away
from data, and leaving more room to grow both in the .note section
(where --build-id can add some), and in the code (.text) section,
before the image grows past one 4kb page.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andi Kleen <ak@suse.de>
---
arch/x86_64/vdso/vdso.lds.S | 47 +++++++++++++++++++++++++++++-------------
1 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/arch/x86_64/vdso/vdso.lds.S b/arch/x86_64/vdso/vdso.lds.S
index b9a60e6..726bc6d 100644
--- a/arch/x86_64/vdso/vdso.lds.S
+++ b/arch/x86_64/vdso/vdso.lds.S
@@ -20,30 +20,47 @@ SECTIONS
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }

+ /* The kernel does not need to know these addresses,
+ so they don't need to be before VDSO_TEXT_OFFSET.
+ Pack these in here to sop up the space used for the alignment. */
+ .note : { *(.note.*) } :text :note
+ .useless : {
+ *(.got.plt) *(.got)
+ *(.gnu.linkonce.d.*)
+ *(.gnu.linkonce.b.*)
+ } :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 et al. If this amount
- is insufficient, ld -shared will barf. Just increase it here. */
+ is insufficient, ld -shared will barf.
+ Just increase VDSO_TEXT_OFFSET (in voffset.h). */
. = VDSO_PRELINK + VDSO_TEXT_OFFSET;

- .text : { *(.text) } :text
- .text.ptr : { *(.text.ptr) } :text
- . = VDSO_PRELINK + 0x900;
- .data : { *(.data) } :text
- .bss : { *(.bss) } :text
+ .rodata : { *(.rodata*) } :text
+ .data : {
+ *(.data*)
+ *(.sdata*)
+ *(.bss*)
+ *(.dynbss*)
+ } :text

- .altinstructions : { *(.altinstructions) } :text
- .altinstr_replacement : { *(.altinstr_replacement) } :text
+ .dynamic : { *(.dynamic) } :text :dynamic

- .note : { *(.note.*) } :text :note
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
- .dynamic : { *(.dynamic) } :text :dynamic
- .useless : {
- *(.got.plt) *(.got)
- *(.gnu.linkonce.d.*)
- *(.dynbss)
- *(.gnu.linkonce.b.*)
+
+ .altinstructions : { *(.altinstructions) } :text
+ .altinstr_replacement : { *(.altinstr_replacement) } :text
+
+ /* Separate actual executed code from other data for happy caches. */
+ . = ALIGN(128);
+
+ .text : {
+ FILL(0x90909090);
+ *(.text .stub .text.* .gnu.linkonce.t.*)
+ KEEP (*(.text.*personality*))
+ . = ALIGN(128);
} :text
}

-
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