linux/arch/arm/vdso/vdso.S

/*
 * Adapted from arm64 version.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/const.h>
#include <asm/page.h>

	__PAGE_ALIGNED_DATA

	.globl vdso_start, vdso_end
	.balign PAGE_SIZE
vdso_start:
	.incbin "arch/arm/vdso/vdso.so"
	.balign PAGE_SIZE
vdso_end:

	.previous
ARM: 8330/1: add VDSO user-space code Place VDSO-related user-space code in arch/arm/kernel/vdso/. It is almost completely written in C with some assembly helpers to load the data page address, sample the counter, and fall back to system calls when necessary. The VDSO can service gettimeofday and clock_gettime when CONFIG_ARM_ARCH_TIMER is enabled and the architected timer is present (and correctly configured). It reads the CP15-based virtual counter to compute high-resolution timestamps. Of particular note is that a post-processing step ("vdsomunge") is necessary to produce a shared object which is architecturally allowed to be used by both soft- and hard-float EABI programs. The 2012 edition of the ARM ABI defines Tag_ABI_VFP_args = 3 "Code is compatible with both the base and VFP variants; the user did not permit non-variadic functions to pass FP parameters/results." Unfortunately current toolchains do not support this tag, which is ideally what we would use. The best available option is to ensure that both EF_ARM_ABI_FLOAT_SOFT and EF_ARM_ABI_FLOAT_HARD are unset in the ELF header's e_flags, indicating that the shared object is "old" and should be accepted for backward compatibility's sake. While binutils < 2.24 appear to produce a vdso.so with both flags clear, 2.24 always sets EF_ARM_ABI_FLOAT_SOFT, with no way to inhibit this behavior. So we have to fix things up with a custom post-processing step. In fact, the VDSO code in glibc does much less validation (including checking these flags) than the code for handling conventional file-backed shared libraries, so this is a bit moot unless glibc's VDSO code becomes more strict. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> 2015-03-25 18:14:22 +00:00			`/*`
			`* Adapted from arm64 version.`
			`*`
			`* Copyright (C) 2012 ARM Limited`
			`*`
			`* This program is free software; you can redistribute it and/or modify`
			`* it under the terms of the GNU General Public License version 2 as`
			`* published by the Free Software Foundation.`
			`*`
			`* This program is distributed in the hope that it will be useful,`
			`* but WITHOUT ANY WARRANTY; without even the implied warranty of`
			`* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the`
			`* GNU General Public License for more details.`
			`*`
			`* You should have received a copy of the GNU General Public License`
			`* along with this program. If not, see <http://www.gnu.org/licenses/>.`
			`*`
			`* Author: Will Deacon <will.deacon@arm.com>`
			`*/`

			`#include <linux/init.h>`
			`#include <linux/linkage.h>`
			`#include <linux/const.h>`
			`#include <asm/page.h>`

			`__PAGE_ALIGNED_DATA`

			`.globl vdso_start, vdso_end`
			`.balign PAGE_SIZE`
			`vdso_start:`
			`.incbin "arch/arm/vdso/vdso.so"`
			`.balign PAGE_SIZE`
			`vdso_end:`

			`.previous`