Re: [PATCH] ARM: Wire up HAVE_SYSCALL_TRACEPOINTS

From: Takuo Koguchi
Date: Thu Feb 02 2012 - 04:24:06 EST

Hello,
I am glad to start getting responses.
(2012/02/01 10:47), Indan Zupancic wrote:
Hello,

CC'ing Roland.

On Thu, December 1, 2011 12:01, takuo.koguchi.sw@xxxxxxxxxxx wrote:
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 44789ef..84181b3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -13,6 +13,7 @@ config ARM
select HAVE_KPROBES if !XIP_KERNEL
select HAVE_KRETPROBES if (HAVE_KPROBES)
select HAVE_FUNCTION_TRACER if (!XIP_KERNEL)
+ select HAVE_SYSCALL_TRACEPOINTS
Your patch totally ignores OABI, it should at least depend on CONFIG_AEABI
and on !CONFIG_OABI_COMPAT.
Right. As Russel King suggested, this patch depends on those configs until very large NR_syscalls is properly handled by ftrace.

select HAVE_FTRACE_MCOUNT_RECORD if (!XIP_KERNEL)
select HAVE_DYNAMIC_FTRACE if (!XIP_KERNEL)
select HAVE_FUNCTION_GRAPH_TRACER if (!THUMB2_KERNEL)
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
new file mode 100644
index 0000000..cabeb67
--- /dev/null
+++ b/arch/arm/include/asm/syscall.h
@@ -0,0 +1,45 @@
+#ifndef _ASM_ARM_SYSCALL_H
+#define _ASM_ARM_SYSCALL_H
+
+extern const unsigned long sys_call_table[];
+
+#include<linux/sched.h>
+
+static inline long syscall_get_nr(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return regs->ARM_r7;
+}
+
+static inline long syscall_get_return_value(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ return regs->ARM_r0;
+}
+
+static inline void syscall_get_arguments(struct task_struct *task,
+ struct pt_regs *regs,
+ unsigned int i, unsigned int n,
+ unsigned long *args)
+{
+ BUG_ON(i);
This is unacceptable, that would make this function useless.

See Rolands patch:

https://lkml.org/lkml/2009/4/24/399 for a better implementation.
Thanks. My apology for the lack of investigation.

+#endif /* _ASM_ARM_SYSCALL_H */
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 7b5cc8d..2509028 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -139,6 +139,7 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define TIF_NEED_RESCHED 1
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_SYSCALL_TRACE 8
+#define TIF_SYSCALL_TRACEPOINT 15
#define TIF_POLLING_NRFLAG 16
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
@@ -150,11 +151,13 @@ extern void vfp_flush_hwstate(struct thread_info *);
#define _TIF_NEED_RESCHED (1<< TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1<< TIF_NOTIFY_RESUME)
#define _TIF_SYSCALL_TRACE (1<< TIF_SYSCALL_TRACE)
+#define _TIF_SYSCALL_TRACEPOINT (1<< TIF_SYSCALL_TRACEPOINT)
#define _TIF_POLLING_NRFLAG (1<< TIF_POLLING_NRFLAG)
#define _TIF_USING_IWMMXT (1<< TIF_USING_IWMMXT)
#define _TIF_FREEZE (1<< TIF_FREEZE)
#define _TIF_RESTORE_SIGMASK (1<< TIF_RESTORE_SIGMASK)
#define _TIF_SECCOMP (1<< TIF_SECCOMP)
+#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT)
What does 'A' stand for?
'A' originally stands for AUDIT. I should have used a better name as there is no _TIF_SYSCALL_AUDIT for ARM.
Probably it is better to define _TIF_WORK_SYSCALL_ENTRY and _TIF_WORK_SYSCALL_EXIT properly.

/*
* Change these and you break ASM code in entry-common.S
diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 4a11237..f4eac2d 100644
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -405,6 +405,9 @@
#define __NR_process_vm_readv (__NR_SYSCALL_BASE+376)
#define __NR_process_vm_writev (__NR_SYSCALL_BASE+377)

+#ifndef __ASSEMBLY__
+#define NR_syscalls 378
+#endif
/*
* The following SWIs are ARM private.
*/
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index b2a27b6..a1577c2 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -87,7 +87,7 @@ ENTRY(ret_from_fork)
get_thread_info tsk
ldr r1, [tsk, #TI_FLAGS] @ check for syscall tracing
mov why, #1
- tst r1, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
+ tst r1, #_TIF_SYSCALL_T_OR_A @ are we tracing syscalls?
beq ret_slow_syscall
mov r1, sp
mov r0, #1 @ trace exit [IP = 1]
@@ -443,7 +443,7 @@ ENTRY(vector_swi)
1:
#endif

- tst r10, #_TIF_SYSCALL_TRACE @ are we tracing syscalls?
+ tst r10, #_TIF_SYSCALL_T_OR_A @ are we tracing syscalls?
bne __sys_trace

cmp scno, #NR_syscalls @ check upper syscall limit
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 483727a..a690c9f 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -28,6 +28,9 @@
#include<asm/system.h>
#include<asm/traps.h>

+#define CREATE_TRACE_POINTS
+#include<trace/events/syscalls.h>
+
#define REG_PC 15
#define REG_PSR 16
/*
@@ -906,6 +909,13 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int
scno)
{
unsigned long ip;
Not used, you get the same info from 'why'.
Sorry. But I do not understand what you suggest here. This is the existing code.


+ if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT))) {
+ if (why)
+ trace_sys_exit(regs, regs->ARM_r0);
+ else
+ trace_sys_enter(regs, scno);
+ }
+
if (!test_thread_flag(TIF_SYSCALL_TRACE))
return scno;
if (!(current->ptrace& PT_PTRACED))


Thanks,

Takuo


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