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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2013-02-16 16:32:19 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2013-02-16 16:32:19 +0000 |
commit | b78eb3e4bbd9a44cb38e6cd5f7fdde4e22a183f4 (patch) | |
tree | 82e3a9b70e21bda79f4a26bf36dd755dcb4160a9 /nuttx/arch/arm/src/armv6-m/vfork.S | |
parent | 54c9fa75c9466f4676d12105dbf4026aeb92adb7 (diff) | |
download | px4-nuttx-b78eb3e4bbd9a44cb38e6cd5f7fdde4e22a183f4.tar.gz px4-nuttx-b78eb3e4bbd9a44cb38e6cd5f7fdde4e22a183f4.tar.bz2 px4-nuttx-b78eb3e4bbd9a44cb38e6cd5f7fdde4e22a183f4.zip |
First cut at support for Cortex-M0
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5655 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/arch/arm/src/armv6-m/vfork.S')
-rw-r--r-- | nuttx/arch/arm/src/armv6-m/vfork.S | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/nuttx/arch/arm/src/armv6-m/vfork.S b/nuttx/arch/arm/src/armv6-m/vfork.S new file mode 100644 index 000000000..0e9b9790d --- /dev/null +++ b/nuttx/arch/arm/src/armv6-m/vfork.S @@ -0,0 +1,144 @@ +/************************************************************************************ + * arch/arm/src/armv6-m/vfork.S + * + * Copyright (C) 2013 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ************************************************************************************/ + +/************************************************************************************ + * Included Files + ************************************************************************************/ + +#include <nuttx/config.h> + +#include "up_vfork.h" + +/************************************************************************************ + * Pre-processor Definitions + ************************************************************************************/ + +/************************************************************************************ + * Global Symbols + ************************************************************************************/ + + .cpu cortex-m0 + .file "vfork.S" + .globl up_vfork + +/************************************************************************************ + * Public Functions + ************************************************************************************/ + +/************************************************************************************ + * Name: vfork + * + * Description: + * The vfork() function has the same effect as fork(), except that the behavior is + * undefined if the process created by vfork() either modifies any data other than + * a variable of type pid_t used to store the return value from vfork(), or returns + * from the function in which vfork() was called, or calls any other function before + * successfully calling _exit() or one of the exec family of functions. + * + * This thin layer implements vfork by simply calling up_vfork() with the vfork() + * context as an argument. The overall sequence is: + * + * 1) User code calls vfork(). vfork() collects context information and + * transfers control up up_vfork(). + * 2) up_vfork()and calls task_vforksetup(). + * 3) task_vforksetup() allocates and configures the child task's TCB. This + * consists of: + * - Allocation of the child task's TCB. + * - Initialization of file descriptors and streams + * - Configuration of environment variables + * - Setup the intput parameters for the task. + * - Initialization of the TCB (including call to up_initial_state() + * 4) up_vfork() provides any additional operating context. up_vfork must: + * - Allocate and initialize the stack + * - Initialize special values in any CPU registers that were not + * already configured by up_initial_state() + * 5) up_vfork() then calls task_vforkstart() + * 6) task_vforkstart() then executes the child thread. + * + * Input Paremeters: + * None + * + * Return: + * Upon successful completion, vfork() returns 0 to the child process and returns + * the process ID of the child process to the parent process. Otherwise, -1 is + * returned to the parent, no child process is created, and errno is set to + * indicate the error. + * + ************************************************************************************/ + + .align 2 + .code 16 + .thumb_func + .globl vfork + .type vfork, function +vfork: + /* Create a stack frame */ + + mov r0, sp /* Save the value of the stack on entry */ + sub sp, sp, #VFORK_SIZEOF /* Allocate the structure on the stack */ + + /* CPU registers */ + /* Save the volatile registers */ + + mov r1, sp + stmia r1!, {r4-r7} /* Save r4-r7 in the structure */ + mov r4, r8 /* Copy high registers to low registers */ + mov r5, r9 + mov r6, r10 + mov r7, fp + stmia r1!, {r4-r7} /* Save r8-r10 and fp in the structure */ + str r0, [r1, #0] /* Save the stack pointer in the structure */ + mov r0, r14 /* Copy lr to a low registers */ + str r0, [r1, #0] /* Save the stack pointer in the structure */ + + /* Then, call up_vfork(), passing it a pointer to the stack structure */ + + mov r0, sp + bl up_vfork + + /* Recover r4-r7 that were destroyed before up_vfork was called */ + + mov r1, sp + ldmia r1!, {r4-r7} + + /* Release the stack data and return the value returned by up_vfork */ + + ldr r1, [sp, #VFORK_LR_OFFSET] + mov r14, r1 + add sp, sp, #VFORK_SIZEOF + bx lr + .size vfork, .-vfork + .end + |