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Subject[C/R ARM][PATCH 1/3] ARM: Rudimentary syscall interfaces
Date
This small commit introduces a global state of system calls for ARM
making it possible for a debugger or checkpointing to gain information
about another process' state with respect to system calls.

The patch is based on this proposal from Roland McGrath:
https://patchwork.kernel.org/patch/32101/

Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Christoffer Dall <christofferdall@christofferdall.dk>
Acked-by: Oren Laadan <orenl@cs.columbia.edu>
---
arch/arm/include/asm/syscall.h | 31 +++++++++++++++++++++++++++++++
arch/arm/kernel/asm-offsets.c | 1 +
arch/arm/kernel/entry-common.S | 8 +++++++-
arch/arm/kernel/ptrace.c | 2 --
arch/arm/kernel/signal.c | 14 +++++++-------
5 files changed, 46 insertions(+), 10 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..3b3248f
--- /dev/null
+++ b/arch/arm/include/asm/syscall.h
@@ -0,0 +1,31 @@
+/*
+ * 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
+
+static inline int syscall_get_nr(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return (int)(task_thread_info(task)->syscall);
+}
+
+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 */
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 4a88125..726a0ad 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -48,6 +48,7 @@ int main(void)
DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
DEFINE(TI_CPU_DOMAIN, offsetof(struct thread_info, cpu_domain));
DEFINE(TI_CPU_SAVE, offsetof(struct thread_info, cpu_context));
+ DEFINE(TI_SYSCALL, offsetof(struct thread_info, syscall));
DEFINE(TI_USED_CP, offsetof(struct thread_info, used_cp));
DEFINE(TI_TP_VALUE, offsetof(struct thread_info, tp_value));
DEFINE(TI_FPSTATE, offsetof(struct thread_info, fpstate));
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 2c1db77..f694f4d 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -30,6 +30,9 @@ ret_fast_syscall:
tst r1, #_TIF_WORK_MASK
bne fast_work_pending

+ mov r2, #-1
+ str r2, [tsk, #TI_SYSCALL]
+
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr

@@ -47,7 +50,6 @@ work_pending:
tst r1, #_TIF_SIGPENDING|_TIF_NOTIFY_RESUME
beq no_work_pending
mov r0, sp @ 'regs'
- mov r2, why @ 'syscall'
bl do_notify_resume
b ret_slow_syscall @ Check work again

@@ -62,6 +64,9 @@ ret_slow_syscall:
ldr r1, [tsk, #TI_FLAGS]
tst r1, #_TIF_WORK_MASK
bne work_pending
+
+ mov r2, #-1
+ str r2, [tsk, #TI_SYSCALL]
no_work_pending:
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr
@@ -274,6 +279,7 @@ ENTRY(vector_swi)
eor scno, scno, #__NR_SYSCALL_BASE @ check OS number
#endif

+ str scno, [tsk, #TI_SYSCALL] @ store syscall nr. globally
stmdb sp!, {r4, r5} @ push fifth and sixth args
tst ip, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
bne __sys_trace
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index a2ea385..44ab437 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -863,8 +863,6 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
ip = regs->ARM_ip;
regs->ARM_ip = why;

- current_thread_info()->syscall = scno;
-
/* the 0x80 provides a way for the tracing parent to distinguish
between a syscall stop and SIGTRAP delivery */
ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index e7714f3..f695239 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -527,7 +527,7 @@ static inline void setup_syscall_restart(struct pt_regs *regs)
static int
handle_signal(unsigned long sig, struct k_sigaction *ka,
siginfo_t *info, sigset_t *oldset,
- struct pt_regs * regs, int syscall)
+ struct pt_regs *regs)
{
struct thread_info *thread = current_thread_info();
struct task_struct *tsk = current;
@@ -537,7 +537,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
/*
* If we were from a system call, check for system call restarting...
*/
- if (syscall) {
+ if (thread->syscall != -1) {
switch (regs->ARM_r0) {
case -ERESTART_RESTARTBLOCK:
case -ERESTARTNOHAND:
@@ -601,7 +601,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
* the kernel can handle, and then we build all the user-level signal handling
* stack-frames in one go after that.
*/
-static void do_signal(struct pt_regs *regs, int syscall)
+static void do_signal(struct pt_regs *regs)
{
struct k_sigaction ka;
siginfo_t info;
@@ -629,7 +629,7 @@ static void do_signal(struct pt_regs *regs, int syscall)
oldset = &current->saved_sigmask;
else
oldset = &current->blocked;
- if (handle_signal(signr, &ka, &info, oldset, regs, syscall) == 0) {
+ if (handle_signal(signr, &ka, &info, oldset, regs) == 0) {
/*
* A signal was successfully delivered; the saved
* sigmask will have been stored in the signal frame,
@@ -647,7 +647,7 @@ static void do_signal(struct pt_regs *regs, int syscall)
/*
* No signal to deliver to the process - restart the syscall.
*/
- if (syscall) {
+ if (current_thread_info()->syscall != -1) {
if (regs->ARM_r0 == -ERESTART_RESTARTBLOCK) {
if (thumb_mode(regs)) {
regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
@@ -689,10 +689,10 @@ static void do_signal(struct pt_regs *regs, int syscall)
}

asmlinkage void
-do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
+do_notify_resume(struct pt_regs *regs, unsigned int thread_flags)
{
if (thread_flags & _TIF_SIGPENDING)
- do_signal(regs, syscall);
+ do_signal(regs);

if (thread_flags & _TIF_NOTIFY_RESUME) {
clear_thread_flag(TIF_NOTIFY_RESUME);
--
1.5.6.5


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