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Message-Id: <1272318223-28438-2-git-send-email-christofferdall@christofferdall.dk>
Date: Mon, 26 Apr 2010 17:43:41 -0400
From: Christoffer Dall <christofferdall@...istofferdall.dk>
To: containers <containers@...ts.linux-foundation.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Christoffer Dall <christofferdall@...istofferdall.dk>,
Roland McGrath <roland@...hat.com>
Subject: [C/R ARM v2][PATCH 1/3] ARM: Rudimentary syscall interfaces
Introduces a few of the system call inspection functions for ARM. The
current motivation is checkpoint restart, but the general interface
requirements are met, making it possible for a debugger or tracer to
obtain information about the system call status of another process.
The patch is in part based on the following proposal from Roland McGrath:
https://patchwork.kernel.org/patch/32101/
Compared to other architectures, the code to implement syscall_get_nr is
somewhat comprehensive. However, it's a result of no globally stored
location for the system call number and the complexity of the ARM ABI with
multiple versions.
Changelog[v2]:
- Get the system call number by inspecting the process instead of
storing the system call number globally on entry to each system
call.
Cc: Roland McGrath <roland@...hat.com>
Signed-off-by: Christoffer Dall <christofferdall@...istofferdall.dk>
Acked-by: Oren Laadan <orenl@...columbia.edu>
---
arch/arm/include/asm/syscall.h | 133 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 133 insertions(+), 0 deletions(-)
create mode 100644 arch/arm/include/asm/syscall.h
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
new file mode 100644
index 0000000..49cb10e
--- /dev/null
+++ b/arch/arm/include/asm/syscall.h
@@ -0,0 +1,133 @@
+/*
+ * syscalls.h - Linux syscall interfaces for ARM
+ *
+ * Copyright (c) 2010 Christoffer Dall
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#ifndef _ASM_ARM_SYSCALLS_H
+#define _ASM_ARM_SYSCALLS_H
+
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+#include <linux/memory.h>
+#include <asm/unistd.h>
+
+static inline int get_swi_instruction(struct task_struct *task,
+ struct pt_regs *regs,
+ unsigned long *instr)
+{
+ struct page *page = NULL;
+ unsigned long instr_addr;
+ unsigned long *ptr;
+ int ret;
+
+ instr_addr = regs->ARM_pc - 4;
+
+ down_read(&task->mm->mmap_sem);
+ ret = get_user_pages(task, task->mm, instr_addr,
+ 1, 0, 0, &page, NULL);
+ up_read(&task->mm->mmap_sem);
+
+ if (ret < 0)
+ return ret;
+
+ ptr = (unsigned long *)kmap_atomic(page, KM_USER1);
+ memcpy(instr,
+ ptr + (instr_addr >> PAGE_SHIFT),
+ sizeof(unsigned long));
+ kunmap_atomic(ptr, KM_USER1);
+
+ page_cache_release(page);
+
+ return 0;
+}
+
+/*
+ * This function essentially duplicates the logic from vector_swi in
+ * arch/arm/kernel/entry-common.S. However, that code is in the
+ * critical path for system calls and is hard to factor out without
+ * compromising performance.
+ */
+static inline int __syscall_get_nr(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ int ret;
+ int scno;
+ unsigned long instr;
+ bool config_oabi = false;
+ bool config_aeabi = false;
+ bool config_arm_thumb = false;
+ bool config_cpu_endian_be8 = false;
+
+#ifdef CONFIG_OABI_COMPAT
+ config_oabi = true;
+#endif
+#ifdef CONFIG_AEABI
+ config_aeabi = true;
+#endif
+#ifdef CONFIG_ARM_THUMB
+ config_arm_thumb = true;
+#endif
+#ifdef CONFIG_CPU_ENDIAN_BE8
+ config_cpu_endian_be8 = true;
+#endif
+#ifdef CONFIG_CPU_ARM710
+ return -1;
+#endif
+
+ if (config_aeabi && !config_oabi) {
+ /* Pure EABI */
+ return regs->ARM_r7;
+ } else if (config_oabi) {
+ if (config_arm_thumb && (regs->ARM_cpsr & PSR_T_BIT))
+ return -1;
+
+ ret = get_swi_instruction(task, regs, &instr);
+ if (ret < 0)
+ return -1;
+
+ if (config_cpu_endian_be8)
+ asm ("rev %[out], %[in]": [out] "=r" (instr):
+ [in] "r" (instr));
+
+ if ((instr & 0x00ffffff) == 0)
+ return regs->ARM_r7; /* EABI call */
+ else
+ return (instr & 0x00ffffff) | __NR_OABI_SYSCALL_BASE;
+ } else {
+ /* Legacy ABI only */
+ if (config_arm_thumb && (regs->ARM_cpsr & PSR_T_BIT)) {
+ /* Thumb mode ABI */
+ scno = regs->ARM_r7 + __NR_SYSCALL_BASE;
+ } else {
+ ret = get_swi_instruction(task, regs, &instr);
+ if (ret < 0)
+ return -1;
+ scno = instr;
+ }
+ return scno & 0x00ffffff;
+ }
+}
+
+static inline int syscall_get_nr(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return __syscall_get_nr(task, regs);
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return regs->ARM_r0;
+}
+
+static inline long syscall_get_error(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return regs->ARM_r0;
+}
+
+#endif /* _ASM_ARM_SYSCALLS_H */
--
1.5.6.5
--
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