Hi Markos, Thanks for finishing this off. Just got a few of minor comments. On 28 September 2015 at 11:10, Markos Chandras <markos.chandras@xxxxxxxxxx> wrote: > diff --git a/arch/mips/vdso/elf.S b/arch/mips/vdso/elf.S > new file mode 100644 > index 000000000000..60c23d0d452c > --- /dev/null > +++ b/arch/mips/vdso/elf.S > @@ -0,0 +1,68 @@ > +/* > + * Copyright (C) 2015 Imagination Technologies > + * Author: Alex Smith <alex.smith@xxxxxxxxxx> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License as published by the > + * Free Software Foundation; either version 2 of the License, or (at your > + * option) any later version. > + */ > + > +#include "vdso.h" > + > +#include <linux/elfnote.h> > +#include <linux/version.h> > + > +ELFNOTE_START(Linux, 0, "a") > + .long LINUX_VERSION_CODE > +ELFNOTE_END > + > +/* > + * The .MIPS.abiflags section must be defined with the FP ABI flags set > + * to 'any' to be able to link with both old and new libraries. > + * Newer toolchains are capable of automatically generating this, but we want > + * to work with older toolchains as well. Therefore, we define the contents of > + * this section here (under different names), and then genvdso will patch > + * it to have the correct name and type. > + * > + * We base the .MIPS.abiflags section on preprocessor definitions rather than > + * CONFIG_* because we need to match the particular ABI we are building the > + * VDSO for. > + * > + * See https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking > + * for the .MIPS.abitflags and .gnu.attributes section description. > + */ s/abitflags/abiflags/ > diff --git a/arch/mips/vdso/vdso.h b/arch/mips/vdso/vdso.h > new file mode 100644 > index 000000000000..64b98967e245 > --- /dev/null > +++ b/arch/mips/vdso/vdso.h > @@ -0,0 +1,79 @@ > +/* > + * Copyright (C) 2015 Imagination Technologies > + * Author: Alex Smith <alex.smith@xxxxxxxxxx> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License as published by the > + * Free Software Foundation; either version 2 of the License, or (at your > + * option) any later version. > + */ > + > +#include <asm/sgidefs.h> > + > +#if _MIPS_SIM != _MIPS_SIM_ABI64 && defined(CONFIG_64BIT) > + > +/* Building 32-bit VDSO for the 64-bit kernel. Fake a 32-bit Kconfig. */ > +#undef CONFIG_64BIT > +#define CONFIG_32BIT 1 > + > +#endif > + > +#ifndef __ASSEMBLY__ > + > +#include <asm/asm.h> > +#include <asm/page.h> > +#include <asm/vdso.h> > + > +static inline unsigned long get_vdso_base(void) > +{ > + unsigned long addr; > + > + /* > + * Get the base load address of the VDSO. We have to avoid generating > + * relocations and references to the GOT because ld.so does not peform > + * relocations on the VDSO. We use the current offset from the VDSO base > + * and perform a PC-relative branch which gives the absolute address in > + * ra, and take the difference. The assembler chokes on > + * "li %0, _start - .", so embed the offset as a word and branch over > + * it. > + * > + * TODO: Is there a better way to do this? Unless somebody else can come up with a better way to do this I'd say this TODO can go :) Also perhaps move the description of what the code is doing (from "We use the current offset from the VDSO base" onwards) down to after the #else since it applies to that code rather than the R6 code which comes first. > + */ > + > +#ifdef CONFIG_CPU_MIPSR6 > + /* > + * We can't use cpu_has_mips_r6 since it will create a relocation > + * in the VDSO because of the global cpu_data[] variable. > + */ I think it would be more correct to say here that cpu_data doesn't even exist to the VDSO because it's a kernel symbol. > + > + /* lapc <symbol> is an alias to addiupc reg, <symbol> - . > + * > + * We can't use addiupc because there is no label-label > + * support for the addiupc reloc > + */ > + __asm__("lapc %0, _start \n" > + : "=r" (addr) : :); Just curious - if lapc is just an alias to addiupc, why does that work but not addiupc? IIRC I did try addiupc previously but removed it because it wasn't working, didn't know about lapc! Thanks, Alex
