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linux-next/arch/x86/vdso/vdso-layout.lds.S
Andy Lutomirski 0e3727a883 x86/vdso: Remove some redundant in-memory section headers
.data doesn't need to be separate from .rodata: they're both readonly.

.altinstructions and .altinstr_replacement aren't needed by anything
except vdso2c; strip them from the final image.

While we're at it, rather than aligning the actual executable text,
just shove some unused-at-runtime data in between real data and
text.

My vdso image is still above 4k, but I'm disinclined to try to
trim it harder for 3.16.  For future trimming, I suspect that these
sections could be moved to later in the file and dropped from
the in-memory image:

.gnu.version and .gnu.version_d   (this may lose versions in gdb)
.eh_frame                         (should be harmless)
.eh_frame_hdr                     (I'm not really sure)
.hash                             (AFAIK nothing needs this section header)

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/2e96d0c49016ea6d026a614ae645e93edd325961.1403129369.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2014-06-19 15:45:26 -07:00

125 lines
2.8 KiB
ArmAsm

#include <asm/vdso.h>
/*
* 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.
*/
#if defined(BUILD_VDSO64)
# define SHDR_SIZE 64
#elif defined(BUILD_VDSO32) || defined(BUILD_VDSOX32)
# define SHDR_SIZE 40
#else
# error unknown VDSO target
#endif
#define NUM_FAKE_SHDRS 13
SECTIONS
{
. = 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) }
.dynamic : { *(.dynamic) } :text :dynamic
.rodata : {
*(.rodata*)
*(.data*)
*(.sdata*)
*(.got.plt) *(.got)
*(.gnu.linkonce.d.*)
*(.bss*)
*(.dynbss*)
*(.gnu.linkonce.b.*)
/*
* Ideally this would live in a C file, but that won't
* work cleanly for x32 until we start building the x32
* C code using an x32 toolchain.
*/
VDSO_FAKE_SECTION_TABLE_START = .;
. = . + NUM_FAKE_SHDRS * SHDR_SIZE;
VDSO_FAKE_SECTION_TABLE_END = .;
} :text
.fake_shstrtab : { *(.fake_shstrtab) } :text
.note : { *(.note.*) } :text :note
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
/*
* Text is well-separated from actual data: there's plenty of
* stuff that isn't used at runtime in between.
*/
.text : { *(.text*) } :text =0x90909090,
/*
* At the end so that eu-elflint stays happy when vdso2c strips
* these. A better implementation would avoid allocating space
* for these.
*/
.altinstructions : { *(.altinstructions) } :text
.altinstr_replacement : { *(.altinstr_replacement) } :text
/*
* The remainder of the vDSO consists of special pages that are
* shared between the kernel and userspace. It needs to be at the
* end so that it doesn't overlap the mapping of the actual
* vDSO image.
*/
. = ALIGN(PAGE_SIZE);
vvar_page = .;
/* Place all vvars at the offsets in asm/vvar.h. */
#define EMIT_VVAR(name, offset) vvar_ ## name = vvar_page + offset;
#define __VVAR_KERNEL_LDS
#include <asm/vvar.h>
#undef __VVAR_KERNEL_LDS
#undef EMIT_VVAR
. = vvar_page + PAGE_SIZE;
hpet_page = .;
. = . + PAGE_SIZE;
. = ALIGN(PAGE_SIZE);
end_mapping = .;
/DISCARD/ : {
*(.discard)
*(.discard.*)
*(__bug_table)
}
}
/*
* 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;
}