Commit-ID: 0e3727a8839c988a3c56170bc8da76d55a16acad Gitweb: http://git.kernel.org/tip/0e3727a8839c988a3c56170bc8da76d55a16acad Author: Andy Lutomirski <l...@amacapital.net> AuthorDate: Wed, 18 Jun 2014 15:59:49 -0700 Committer: H. Peter Anvin <h...@linux.intel.com> CommitDate: Thu, 19 Jun 2014 15:45:26 -0700
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 <l...@amacapital.net> Link: http://lkml.kernel.org/r/2e96d0c49016ea6d026a614ae645e93edd325961.1403129369.git.l...@amacapital.net Signed-off-by: H. Peter Anvin <h...@linux.intel.com> --- arch/x86/vdso/vdso-fakesections.c | 3 --- arch/x86/vdso/vdso-layout.lds.S | 43 +++++++++++++++++++++------------------ arch/x86/vdso/vdso2c.h | 4 +++- 3 files changed, 26 insertions(+), 24 deletions(-) diff --git a/arch/x86/vdso/vdso-fakesections.c b/arch/x86/vdso/vdso-fakesections.c index 56927a7..aa5fbfa 100644 --- a/arch/x86/vdso/vdso-fakesections.c +++ b/arch/x86/vdso/vdso-fakesections.c @@ -16,9 +16,6 @@ const char fake_shstrtab[] __attribute__((section(".fake_shstrtab"))) = ".rodata\0" ".fake_shstrtab\0" /* Yay, self-referential code. */ ".note\0" - ".data\0" - ".altinstructions\0" - ".altinstr_replacement\0" ".eh_frame_hdr\0" ".eh_frame\0" ".text"; diff --git a/arch/x86/vdso/vdso-layout.lds.S b/arch/x86/vdso/vdso-layout.lds.S index e4cbc21..9197544 100644 --- a/arch/x86/vdso/vdso-layout.lds.S +++ b/arch/x86/vdso/vdso-layout.lds.S @@ -14,7 +14,7 @@ # error unknown VDSO target #endif -#define NUM_FAKE_SHDRS 16 +#define NUM_FAKE_SHDRS 13 SECTIONS { @@ -28,15 +28,17 @@ SECTIONS .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*) + *(.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 @@ -50,28 +52,29 @@ SECTIONS .fake_shstrtab : { *(.fake_shstrtab) } :text - .data : { - *(.data*) - *(.sdata*) - *(.got.plt) *(.got) - *(.gnu.linkonce.d.*) - *(.bss*) - *(.dynbss*) - *(.gnu.linkonce.b.*) - } - .altinstructions : { *(.altinstructions) } - .altinstr_replacement : { *(.altinstr_replacement) } + .note : { *(.note.*) } :text :note + + .eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr + .eh_frame : { KEEP (*(.eh_frame)) } :text + /* - * Align the actual code well away from the non-instruction data. - * This is the best thing for the I-cache. + * Text is well-separated from actual data: there's plenty of + * stuff that isn't used at runtime in between. */ - . = ALIGN(0x100); .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 diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h index f01ed4b..f42e2dd 100644 --- a/arch/x86/vdso/vdso2c.h +++ b/arch/x86/vdso/vdso2c.h @@ -92,7 +92,9 @@ static void BITSFUNC(copy_section)(struct BITSFUNC(fake_sections) *out, { uint64_t flags = GET_LE(&in->sh_flags); - bool copy = flags & SHF_ALLOC; + bool copy = flags & SHF_ALLOC && + strcmp(name, ".altinstructions") && + strcmp(name, ".altinstr_replacement"); if (!copy) return; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
