diff options
author | Alex Smith <alex.smith@imgtec.com> | 2015-10-21 09:54:38 +0100 |
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committer | Ralf Baechle <ralf@linux-mips.org> | 2015-11-11 08:36:36 +0100 |
commit | ebb5e78cc63417a35254a791de66e1cc84f963cc (patch) | |
tree | 49814946abe594cb8e7a11ce8d0a5fdaabb49d31 /arch/mips/vdso/vdso.h | |
parent | 22773aa9b95657f0adc2b5342428d9da7a6d5d02 (diff) |
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: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Markos 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: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/vdso/vdso.h')
-rw-r--r-- | arch/mips/vdso/vdso.h | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/arch/mips/vdso/vdso.h b/arch/mips/vdso/vdso.h new file mode 100644 index 000000000000..0bb6b1adc385 --- /dev/null +++ b/arch/mips/vdso/vdso.h @@ -0,0 +1,80 @@ +/* + * Copyright (C) 2015 Imagination Technologies + * Author: Alex Smith <alex.smith@imgtec.com> + * + * 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 +#ifndef __ASSEMBLY__ +#include <asm-generic/atomic64.h> +#endif +#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; + + /* + * We can't use cpu_has_mips_r6 since it needs the cpu_data[] + * kernel symbol. + */ +#ifdef CONFIG_CPU_MIPSR6 + /* + * 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) : :); +#else + /* + * 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. + * + */ + + __asm__( + " .set push \n" + " .set noreorder \n" + " bal 1f \n" + " nop \n" + " .word _start - . \n" + "1: lw %0, 0($31) \n" + " " STR(PTR_ADDU) " %0, $31, %0 \n" + " .set pop \n" + : "=r" (addr) + : + : "$31"); +#endif /* CONFIG_CPU_MIPSR6 */ + + return addr; +} + +static inline const union mips_vdso_data *get_vdso_data(void) +{ + return (const union mips_vdso_data *)(get_vdso_base() - PAGE_SIZE); +} + +#endif /* __ASSEMBLY__ */ |