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Subject[PATCH 5/6] trace, powerpc: Implement raw syscall tracepoints on PowerPC
Date
From: Ian Munsie <imunsie@au.ibm.com>

This patch implements the raw syscall tracepoints on PowerPC and exports
them for ftrace syscalls to use.

To minimise reworking existing code, I slightly re-ordered the thread
info flags such that the new TIF_SYSCALL_TRACEPOINT bit would still fit
within the 16 bits of the andi. instruction's UI field. The instructions
in question are in /arch/powerpc/kernel/entry_{32,64}.S to and the
_TIF_SYSCALL_T_OR_A with the thread flags to see if system call tracing
is enabled.
In the case of 64bit PowerPC, arch_syscall_addr and
arch_syscall_match_sym_name are overridden to allow ftrace syscalls to
work given the unusual system call table structure and symbol names that
start with a period.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/ftrace.h | 10 ++++++++++
arch/powerpc/include/asm/syscall.h | 5 +++++
arch/powerpc/include/asm/thread_info.h | 7 +++++--
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/ftrace.c | 8 ++++++++
arch/powerpc/kernel/ptrace.c | 10 ++++++++++
7 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 7d69e9b..a0e8e02 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -134,6 +134,7 @@ config PPC
select HAVE_GENERIC_HARDIRQS
select HAVE_SPARSE_IRQ
select IRQ_PER_CPU
+ select HAVE_SYSCALL_TRACEPOINTS

config EARLY_PRINTK
bool
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index dde1296..0a08902 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -60,4 +60,14 @@ struct dyn_arch_ftrace {

#endif

+#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
+/*
+ * Compare the symbol name with the system call name. Skip the .sys or .SyS
+ * prefix from the symbol name and the sys prefix from the system call name and
+ * just match the rest. This is only needed on ppc64 since symbol names on
+ * 32bit do not start with a period so the generic function will work.
+ */
+#define arch_syscall_match_sym_name(sym, name) !strcmp(sym + 4, name + 3)
+#endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */
+
#endif /* _ASM_POWERPC_FTRACE */
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 23913e9..b54b2ad 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -15,6 +15,11 @@

#include <linux/sched.h>

+/* ftrace syscalls requires exporting the sys_call_table */
+#ifdef CONFIG_FTRACE_SYSCALLS
+extern const unsigned long *sys_call_table;
+#endif /* CONFIG_FTRACE_SYSCALLS */
+
static inline long syscall_get_nr(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 65eb859..4403f09 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -110,7 +110,8 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NOERROR 12 /* Force successful syscall return */
#define TIF_NOTIFY_RESUME 13 /* callback before returning to user */
#define TIF_FREEZE 14 /* Freezing for suspend */
-#define TIF_RUNLATCH 15 /* Is the runlatch enabled? */
+#define TIF_SYSCALL_TRACEPOINT 15 /* syscall tracepoint instrumentation */
+#define TIF_RUNLATCH 16 /* Is the runlatch enabled? */

/* as above, but as bit values */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -127,8 +128,10 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_NOERROR (1<<TIF_NOERROR)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
#define _TIF_FREEZE (1<<TIF_FREEZE)
+#define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT)
#define _TIF_RUNLATCH (1<<TIF_RUNLATCH)
-#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP)
+#define _TIF_SYSCALL_T_OR_A (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)

#define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
_TIF_NOTIFY_RESUME)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 3bb2a3e..fe1ac47 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -105,6 +105,7 @@ obj64-$(CONFIG_AUDIT) += compat_audit.o

obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
+obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o

obj-$(CONFIG_PPC_PERF_CTRS) += perf_event.o
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index ce1f3e4..bf99cfa 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -22,6 +22,7 @@
#include <asm/cacheflush.h>
#include <asm/code-patching.h>
#include <asm/ftrace.h>
+#include <asm/syscall.h>


#ifdef CONFIG_DYNAMIC_FTRACE
@@ -600,3 +601,10 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
+unsigned long __init arch_syscall_addr(int nr)
+{
+ return sys_call_table[nr*2];
+}
+#endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 9065369..b6ff0cb 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -29,6 +29,7 @@
#include <linux/signal.h>
#include <linux/seccomp.h>
#include <linux/audit.h>
+#include <trace/syscall.h>
#ifdef CONFIG_PPC32
#include <linux/module.h>
#endif
@@ -40,6 +41,9 @@
#include <asm/pgtable.h>
#include <asm/system.h>

+#define CREATE_TRACE_POINTS
+#include <trace/events/syscalls.h>
+
/*
* The parameter save area on the stack is used to store arguments being passed
* to callee function and is located at fixed offset from stack pointer.
@@ -1691,6 +1695,9 @@ long do_syscall_trace_enter(struct pt_regs *regs)
*/
ret = -1L;

+ if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
+ trace_sys_enter(regs, regs->gpr[0]);
+
if (unlikely(current->audit_context)) {
#ifdef CONFIG_PPC64
if (!is_32bit_task())
@@ -1719,6 +1726,9 @@ void do_syscall_trace_leave(struct pt_regs *regs)
audit_syscall_exit((regs->ccr&0x10000000)?AUDITSC_FAILURE:AUDITSC_SUCCESS,
regs->result);

+ if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
+ trace_sys_exit(regs, regs->result);
+
step = test_thread_flag(TIF_SINGLESTEP);
if (step || test_thread_flag(TIF_SYSCALL_TRACE))
tracehook_report_syscall_exit(regs, step);
--
1.7.2.3


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