ARM: support syscall tracing

PATCH Superseded Wade Farnsworth 2 participants 2 messages Aug 13, 2012 – Aug 14, 2012

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Arm (32-bit) ptrace support

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Wade Farnsworth

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2012-08-13 17:03 UTC #0 lore raw

PATCH 1/1 ARM: support syscall tracing

As specified by ftrace-design.txt, TIF_SYSCALL_TRACEPOINT was added, as well as NR_syscalls in asm/unistd.h. Additionally, __sys_trace was modified to call trace_sys_enter and trace_sys_exit when appropriate.

Tests #2 - #4 of "perf test" now complete successfully.

Signed-off-by Steven Walter <[email protected]>

Signed-off-by Wade Farnsworth <[email protected]>

---

This patch is an update of one I posted some months ago. It has been rebased to Linus's current HEAD.

 arch/arm/Kconfig                   |    1 +
 arch/arm/include/asm/syscall.h     |    4 ++++
 arch/arm/include/asm/thread_info.h |    2 ++
 arch/arm/include/asm/unistd.h      |    8 ++++++++
 arch/arm/kernel/entry-common.S     |   12 +++++++++++-
 arch/arm/kernel/ptrace.c           |   23 ++++++++++++++++++-----
 6 files changed, 44 insertions(+), 6 deletions(-)

arch/arm/Kconfig +1 -0

index e91c7cd..983e9eb 100644
@@ -16,6 +16,7 @@ config ARM
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
+	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES if !XIP_KERNEL
 	select HAVE_KRETPROBES if (HAVE_KPROBES)
 	select HAVE_FUNCTION_TRACER if (!XIP_KERNEL)

arch/arm/include/asm/syscall.h +4 -0

index c334a23..47486a4 100644
@@ -9,6 +9,10 @@
 
 #include <linux/err.h>
 
+#include <asm/unistd.h>
+
+#define NR_syscalls (__NR_syscalls)
+
 extern const unsigned long sys_call_table[];
 
 static inline int syscall_get_nr(struct task_struct *task,

arch/arm/include/asm/thread_info.h +2 -0

index af7b0bd..d3e4410 100644
@@ -154,6 +154,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_RESTORE_SIGMASK	20
 #define TIF_SECCOMP		21
 #define TIF_SWITCH_MM		22	/* deferred switch_mm */
+#define TIF_SYSCALL_TRACEPOINT	23
 
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)

@@ -163,6 +164,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 
 /* Checks for any syscall work in entry-common.S */
 #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT)

arch/arm/include/asm/unistd.h +8 -0

index 0cab47d..a566ec2 100644
@@ -406,6 +406,14 @@
 #define __NR_process_vm_writev		(__NR_SYSCALL_BASE+377)
 
 /*
+ * This may need to be greater than __NR_last_syscall+1 in order to
+ * account for the padding in the syscall table
+ */
+#ifdef __KERNEL__
+#define __NR_syscalls  (380)
+#endif /* __KERNEL__ */
+
+/*
  * The following SWIs are ARM private.
  */
 #define __ARM_NR_BASE			(__NR_SYSCALL_BASE+0x0f0000)

arch/arm/kernel/entry-common.S +11 -1

index 978eac5..51b64c1 100644
@@ -94,6 +94,15 @@ ENDPROC(ret_from_fork)
 	.equ NR_syscalls,0
 #define CALL(x) .equ NR_syscalls,NR_syscalls+1
 #include "calls.S"
+
+/*
+ * Ensure that the system call table is equal to __NR_syscalls,
+ * which is the value the rest of the system sees
+ */
+.ifne NR_syscalls - __NR_syscalls
+.error "__NR_syscalls is not equal to the size of the syscall table"
+.endif
+
 #undef CALL
 #define CALL(x) .long x

@@ -415,7 +424,8 @@ local_restart:
 1:
 #endif
 
-	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
+	tst     r10, #_TIF_SYSCALL_WORK
+	tsteq   r10, #_TIF_SYSCALL_TRACEPOINT
 	bne	__sys_trace
 
 	cmp	scno, #NR_syscalls		@ check upper syscall limit

arch/arm/kernel/ptrace.c +18 -5

index 3e0fc5f..a2d46ed 100644
@@ -30,6 +30,9 @@
 #include <asm/pgtable.h>
 #include <asm/traps.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
 #define REG_PC	15
 #define REG_PSR	16
 /*

@@ -918,7 +921,8 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 {
 	unsigned long ip;
 
-	if (!test_thread_flag(TIF_SYSCALL_TRACE))
+	if (!test_thread_flag(TIF_SYSCALL_TRACE) &&
+	    !test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		return scno;
 
 	current_thread_info()->syscall = scno;

@@ -930,10 +934,19 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 	ip = regs->ARM_ip;
 	regs->ARM_ip = dir;
 
-	if (dir == PTRACE_SYSCALL_EXIT)
-		tracehook_report_syscall_exit(regs, 0);
-	else if (tracehook_report_syscall_entry(regs))
-		current_thread_info()->syscall = -1;
+	if (test_thread_flag(TIF_SYSCALL_TRACE)) {
+		if (dir == PTRACE_SYSCALL_EXIT)
+			tracehook_report_syscall_exit(regs, 0);
+		else if (tracehook_report_syscall_entry(regs))
+			current_thread_info()->syscall = -1;
+	}
+
+	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
+		if (dir == PTRACE_SYSCALL_EXIT)
+			trace_sys_exit(regs, scno);
+		else
+			trace_sys_enter(regs, scno);
+	}
 
 	regs->ARM_ip = ip;
 	return current_thread_info()->syscall;

Signature · 1 line

1.7.0.4

Will Deacon

2012-08-14 16:11 UTC #1 lore raw

PATCH 1/1 ARM: support syscall tracing

Hi Wade,

Thanks for the new patch. A few comments inline.

Quoted 13 lines · Wade Farnsworth

arch/arm/include/asm/thread_info.h +1 -0

index af7b0bd..d3e4410 100644
@@ -154,6 +154,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_RESTORE_SIGMASK	20
 #define TIF_SECCOMP		21
 #define TIF_SWITCH_MM		22	/* deferred switch_mm */
+#define TIF_SYSCALL_TRACEPOINT	23
 
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)

arch/arm/include/asm/thread_info.h extern int vfp_restore_user_hwstate(struct user_vfp __user *, · line 167

Quoted 4 lines

arch/arm/include/asm/thread_info.h +1 -0

@@ -163,6 +164,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)

Can you add this to the definition of _TIF_SYSCALL_WORK as well please?

Quoted 21 lines

arch/arm/kernel/entry-common.S +9 -0

index 978eac5..51b64c1 100644
@@ -94,6 +94,15 @@ ENDPROC(ret_from_fork)
 	.equ NR_syscalls,0
 #define CALL(x) .equ NR_syscalls,NR_syscalls+1
 #include "calls.S"
+
+/*
+ * Ensure that the system call table is equal to __NR_syscalls,
+ * which is the value the rest of the system sees
+ */
+.ifne NR_syscalls - __NR_syscalls
+.error "__NR_syscalls is not equal to the size of the syscall table"
+.endif
+
 #undef CALL
 #define CALL(x) .long x

arch/arm/kernel/entry-common.S local_restart: · line 429

Quoted 7 lines

arch/arm/kernel/entry-common.S +2 -1

@@ -415,7 +424,8 @@ local_restart:
 1:
 #endif
 
-	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
+	tst     r10, #_TIF_SYSCALL_WORK
+	tsteq   r10, #_TIF_SYSCALL_TRACEPOINT
 	bne	__sys_trace

Then we don't need this hunk.

Quoted 35 lines

arch/arm/kernel/ptrace.c +8 -5

index 3e0fc5f..a2d46ed 100644
@@ -30,6 +30,9 @@
 #include <asm/pgtable.h>
 #include <asm/traps.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
 #define REG_PC	15
 #define REG_PSR	16
 /*

@@ -918,7 +921,8 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 {
 	unsigned long ip;
 
-	if (!test_thread_flag(TIF_SYSCALL_TRACE))
+	if (!test_thread_flag(TIF_SYSCALL_TRACE) &&
+	    !test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		return scno;
 
 	current_thread_info()->syscall = scno;

@@ -930,10 +934,19 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 	ip = regs->ARM_ip;
 	regs->ARM_ip = dir;
 
-	if (dir == PTRACE_SYSCALL_EXIT)
-		tracehook_report_syscall_exit(regs, 0);
-	else if (tracehook_report_syscall_entry(regs))
-		current_thread_info()->syscall = -1;
+	if (test_thread_flag(TIF_SYSCALL_TRACE)) {
+		if (dir == PTRACE_SYSCALL_EXIT)
+			tracehook_report_syscall_exit(regs, 0);

arch/arm/kernel/ptrace.c static int ptrace_syscall_trace(struct pt_regs *regs, int scno, · line 949

Quoted 10 lines

arch/arm/kernel/ptrace.c +10 -0

+		else if (tracehook_report_syscall_entry(regs))
+			current_thread_info()->syscall = -1;
+	}
+
+	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
+		if (dir == PTRACE_SYSCALL_EXIT)
+			trace_sys_exit(regs, scno);
+		else
+			trace_sys_enter(regs, scno);
+	}

I reckon the TRACEPOINT stuff would be better off inside the syscall_trace_{enter,exit} functions. They don't modify the syscall number, so they can just use the return value from ptrace_syscall_trace before the audit hook invoked.

Will