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Commit ebb5e78c authored by Alex Smith's avatar Alex Smith Committed by Ralf Baechle
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MIPS: Initial implementation of a VDSO 



Add an initial implementation of a proper (i.e. an ELF shared library)
VDSO. With this commit it does not export any symbols, it only replaces
the current signal return trampoline page. A later commit will add user
implementations of gettimeofday()/clock_gettime().

To support both new toolchains and old ones which don't generate ABI
flags section, we define its content manually and then use a tool
(genvdso) to patch up the section to have the correct name and type.
genvdso also extracts symbol offsets ({,rt_}sigreturn) needed by the
kernel, and generates a C file containing a "struct mips_vdso_image"
containing both the VDSO data and these offsets. This C file is
compiled into the kernel.

On 64-bit kernels we require a different VDSO for each supported ABI,
so we may build up to 3 different VDSOs. The VDSO to use is selected by
the mips_abi structure.

A kernel/user shared data page is created and mapped below the VDSO
image. This is currently empty, but will be used by the user time
function implementations which are added later.

[markos.chandras@imgtec.com:
- Add more comments
- Move abi detection in genvdso.h since it's the get_symbol function
that needs it.
- Add an R6 specific way to calculate the base address of VDSO in order
to avoid the branch instruction which affects performance.
- Do not patch .gnu.attributes since it's not needed for dynamic linking.
- Simplify Makefile a little bit.
- checkpatch fixes
- Restrict VDSO support for binutils < 2.25 for pre-R6
- Include atomic64.h for O32 variant on MIPS64]

Signed-off-by: default avatarAlex Smith <alex.smith@imgtec.com>
Signed-off-by: default avatarMarkos Chandras <markos.chandras@imgtec.com>
Cc: Matthew Fortune <matthew.fortune@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11337/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 22773aa9

arch/mips/Kbuild

+1 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ obj- := $(platform-) 
obj-y += kernel/

obj-y += mm/

obj-y += net/

obj-y += vdso/



ifdef CONFIG_KVM

obj-y += kvm/

arch/mips/include/asm/abi.h

+3 −2
Original line number Diff line number Diff line
@@ -11,19 +11,20 @@ 


#include <asm/signal.h>

#include <asm/siginfo.h>

#include <asm/vdso.h>



struct mips_abi {

	int (* const setup_frame)(void *sig_return, struct ksignal *ksig,

				  struct pt_regs *regs, sigset_t *set);

	const unsigned long	signal_return_offset;

	int (* const setup_rt_frame)(void *sig_return, struct ksignal *ksig,

				     struct pt_regs *regs, sigset_t *set);

	const unsigned long	rt_signal_return_offset;

	const unsigned long	restart;



	unsigned	off_sc_fpregs;

	unsigned	off_sc_fpc_csr;

	unsigned	off_sc_used_math;



	struct mips_vdso_image *vdso;

};



#endif /* _ASM_ABI_H */

arch/mips/include/asm/elf.h

+7 −0
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#ifndef _ASM_ELF_H

#define _ASM_ELF_H



#include <linux/auxvec.h>

#include <linux/fs.h>

#include <uapi/linux/elf.h>
@@ -419,6 +420,12 @@ extern const char *__elf_platform; 
#define ELF_ET_DYN_BASE		(TASK_SIZE / 3 * 2)

#endif



#define ARCH_DLINFO							\

do {									\

	NEW_AUX_ENT(AT_SYSINFO_EHDR,					\

		    (unsigned long)current->mm->context.vdso);		\

} while (0)



#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1

struct linux_binprm;

extern int arch_setup_additional_pages(struct linux_binprm *bprm,

arch/mips/include/asm/processor.h

+1 −7
Original line number Diff line number Diff line
@@ -36,12 +36,6 @@ extern unsigned int vced_count, vcei_count; 
 */

#define HAVE_ARCH_PICK_MMAP_LAYOUT 1



/*

 * A special page (the vdso) is mapped into all processes at the very

 * top of the virtual memory space.

 */

#define SPECIAL_PAGES_SIZE PAGE_SIZE



#ifdef CONFIG_32BIT

#ifdef CONFIG_KVM_GUEST

/* User space process size is limited to 1GB in KVM Guest Mode */
@@ -80,7 +74,7 @@ extern unsigned int vced_count, vcei_count; 


#endif



#define STACK_TOP	((TASK_SIZE & PAGE_MASK) - SPECIAL_PAGES_SIZE)

#define STACK_TOP	(TASK_SIZE & PAGE_MASK)



/*

 * This decides where the kernel will search for a free chunk of vm

arch/mips/include/asm/vdso.h

+57 −16
Original line number Diff line number Diff line 
/*

 * This file is subject to the terms and conditions of the GNU General Public

 * License.  See the file "COPYING" in the main directory of this archive

 * for more details.

 * Copyright (C) 2015 Imagination Technologies

 * Author: Alex Smith <alex.smith@imgtec.com>

 *

 * Copyright (C) 2009 Cavium Networks

 * 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.

 */



#ifndef __ASM_VDSO_H

#define __ASM_VDSO_H



#include <linux/types.h>

#include <linux/mm_types.h>



/**

 * struct mips_vdso_image - Details of a VDSO image.

 * @data: Pointer to VDSO image data (page-aligned).

 * @size: Size of the VDSO image data (page-aligned).

 * @off_sigreturn: Offset of the sigreturn() trampoline.

 * @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.

 * @mapping: Special mapping structure.

 *

 * This structure contains details of a VDSO image, including the image data

 * and offsets of certain symbols required by the kernel. It is generated as

 * part of the VDSO build process, aside from the mapping page array, which is

 * populated at runtime.

 */

struct mips_vdso_image {

	void *data;

	unsigned long size;



#ifdef CONFIG_32BIT

struct mips_vdso {

	u32 signal_trampoline[2];

	u32 rt_signal_trampoline[2];

	unsigned long off_sigreturn;

	unsigned long off_rt_sigreturn;



	struct vm_special_mapping mapping;

};

#else  /* !CONFIG_32BIT */

struct mips_vdso {

	u32 o32_signal_trampoline[2];

	u32 o32_rt_signal_trampoline[2];

	u32 rt_signal_trampoline[2];

	u32 n32_rt_signal_trampoline[2];



/*

 * The following structures are auto-generated as part of the build for each

 * ABI by genvdso, see arch/mips/vdso/Makefile.

 */



extern struct mips_vdso_image vdso_image;



#ifdef CONFIG_MIPS32_O32

extern struct mips_vdso_image vdso_image_o32;

#endif



#ifdef CONFIG_MIPS32_N32

extern struct mips_vdso_image vdso_image_n32;

#endif



/**

 * union mips_vdso_data - Data provided by the kernel for the VDSO.

 *

 * This structure contains data needed by functions within the VDSO. It is

 * populated by the kernel and mapped read-only into user memory.

 *

 * Note: Care should be taken when modifying as the layout must remain the same

 * for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).

 */

union mips_vdso_data {

	struct {

	};



	u8 page[PAGE_SIZE];

};

#endif /* CONFIG_32BIT */



#endif /* __ASM_VDSO_H */