This revamps the vDSO linker script to lay things out with the best
packing of the data and good, separate alignment of the code. The
rigid layout using VDSO_TEXT_OFFSET no longer matters to the kernel.
I've moved the layout parts of the linker script into a new include
file, vdso-layout.lds.S; this is in preparation for sharing the script
for the 32-bit vDSO builds too.
Signed-off-by: Roland McGrath <[email protected]>
---
arch/x86/vdso/vdso-layout.lds.S | 64 ++++++++++++++++++++++++
arch/x86/vdso/vdso.lds.S | 102 ++++++++++-----------------------------
arch/x86/vdso/voffset.h | 1 -
3 files changed, 89 insertions(+), 78 deletions(-)
create mode 100644 arch/x86/vdso/vdso-layout.lds.S
delete mode 100644 arch/x86/vdso/voffset.h
diff --git a/arch/x86/vdso/vdso-layout.lds.S b/arch/x86/vdso/vdso-layout.lds.S
new file mode 100644
index 0000000..634a2cf
--- /dev/null
+++ b/arch/x86/vdso/vdso-layout.lds.S
@@ -0,0 +1,64 @@
+/*
+ * Linker script for vDSO. This is an ELF shared object prelinked to
+ * its virtual address, and with only one read-only segment.
+ * This script controls its layout.
+ */
+
+SECTIONS
+{
+ . = VDSO_PRELINK + SIZEOF_HEADERS;
+
+ .hash : { *(.hash) } :text
+ .gnu.hash : { *(.gnu.hash) }
+ .dynsym : { *(.dynsym) }
+ .dynstr : { *(.dynstr) }
+ .gnu.version : { *(.gnu.version) }
+ .gnu.version_d : { *(.gnu.version_d) }
+ .gnu.version_r : { *(.gnu.version_r) }
+
+ .note : { *(.note.*) } :text :note
+
+ .eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
+ .eh_frame : { KEEP (*(.eh_frame)) } :text
+
+ .dynamic : { *(.dynamic) } :text :dynamic
+
+ .rodata : { *(.rodata*) } :text
+ .data : {
+ *(.data*)
+ *(.sdata*)
+ *(.got.plt) *(.got)
+ *(.gnu.linkonce.d.*)
+ *(.bss*)
+ *(.dynbss*)
+ *(.gnu.linkonce.b.*)
+ }
+
+ .altinstructions : { *(.altinstructions) }
+ .altinstr_replacement : { *(.altinstr_replacement) }
+
+ /*
+ * Align the actual code well away from the non-instruction data.
+ * This is the best thing for the I-cache.
+ */
+ . = ALIGN(0x100);
+
+ .text : { *(.text*) } :text =0x90909090
+}
+
+/*
+ * Very old versions of ld do not recognize this name token; use the constant.
+ */
+#define PT_GNU_EH_FRAME 0x6474e550
+
+/*
+ * We must supply the ELF program headers explicitly to get just one
+ * PT_LOAD segment, and set the flags explicitly to make segments read-only.
+ */
+PHDRS
+{
+ text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
+ dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
+ note PT_NOTE FLAGS(4); /* PF_R */
+ eh_frame_hdr PT_GNU_EH_FRAME;
+}
diff --git a/arch/x86/vdso/vdso.lds.S b/arch/x86/vdso/vdso.lds.S
index d40d0e9..4e5dd3b 100644
--- a/arch/x86/vdso/vdso.lds.S
+++ b/arch/x86/vdso/vdso.lds.S
@@ -1,89 +1,37 @@
/*
- * Linker script for vsyscall DSO. The vsyscall page is an ELF shared
- * object prelinked to its virtual address, and with only one read-only
- * segment (that fits in one page). This script controls its layout.
+ * Linker script for 64-bit vDSO.
+ * We #include the file to define the layout details.
+ * Here we only choose the prelinked virtual address.
+ *
+ * This file defines the version script giving the user-exported symbols in
+ * the DSO. We can define local symbols here called VDSO* to make their
+ * values visible using the asm-x86/vdso.h macros from the kernel proper.
*/
-#include <asm/asm-offsets.h>
-#include "voffset.h"
#define VDSO_PRELINK 0xffffffffff700000
+#include "vdso-layout.lds.S"
/*
- * Symbols we define here called VDSO* get their values into vdso-syms.lds
- * and become visible to the kernel itself.
+ * This controls what userland symbols we export from the vDSO.
*/
-VDSO64_PRELINK = VDSO_PRELINK;
-
-#define VEXTERN(x) VDSO64_ ## x = vdso_ ## x;
-#include "vextern.h"
-#undef VEXTERN
-
-SECTIONS
-{
- . = VDSO_PRELINK + SIZEOF_HEADERS;
-
- .hash : { *(.hash) } :text
- .gnu.hash : { *(.gnu.hash) }
- .dynsym : { *(.dynsym) }
- .dynstr : { *(.dynstr) }
- .gnu.version : { *(.gnu.version) }
- .gnu.version_d : { *(.gnu.version_d) }
- .gnu.version_r : { *(.gnu.version_r) }
-
- /* 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. */
- . = VDSO_PRELINK + VDSO_TEXT_OFFSET;
-
- .text : { *(.text*) } :text
- .rodata : { *(.rodata*) } :text
- .data : {
- *(.data*)
- *(.sdata*)
- *(.bss*)
- *(.dynbss*)
- } :text
-
- .altinstructions : { *(.altinstructions) } :text
- .altinstr_replacement : { *(.altinstr_replacement) } :text
-
- .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.*)
- *(.gnu.linkonce.b.*)
- } :text
+VERSION {
+ LINUX_2.6 {
+ global:
+ clock_gettime;
+ __vdso_clock_gettime;
+ gettimeofday;
+ __vdso_gettimeofday;
+ getcpu;
+ __vdso_getcpu;
+ local: *;
+ };
}
-/*
- * We must supply the ELF program headers explicitly to get just one
- * PT_LOAD segment, and set the flags explicitly to make segments read-only.
- */
-PHDRS
-{
- text PT_LOAD FILEHDR PHDRS FLAGS(5); /* PF_R|PF_X */
- dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
- note PT_NOTE FLAGS(4); /* PF_R */
- eh_frame_hdr 0x6474e550; /* PT_GNU_EH_FRAME, but ld doesn't match the name */
-}
+VDSO64_PRELINK = VDSO_PRELINK;
/*
- * This controls what symbols we export from the DSO.
+ * Define VDSO64_x for each VEXTERN(x), for use via VDSO64_SYMBOL.
*/
-VERSION
-{
- LINUX_2.6 {
- global:
- clock_gettime;
- __vdso_clock_gettime;
- gettimeofday;
- __vdso_gettimeofday;
- getcpu;
- __vdso_getcpu;
- local: *;
- };
-}
+#define VEXTERN(x) VDSO64_ ## x = vdso_ ## x;
+#include "vextern.h"
+#undef VEXTERN
diff --git a/arch/x86/vdso/voffset.h b/arch/x86/vdso/voffset.h
deleted file mode 100644
index 4af67c7..0000000
--- a/arch/x86/vdso/voffset.h
+++ /dev/null
@@ -1 +0,0 @@
-#define VDSO_TEXT_OFFSET 0x600
-
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