[PATCH 2/2 v2] tracing/syscalls: support for syscalls tracing on x86-64

Frederic Weisbecker
2009-03-13T14:43:01Z

Some bits for syscalls tracing remain arch dependent, including:

- tasks trapping on syscalls entry/exit by using TIF_FLAFS
- call ftrace_syscall_{enter,exit}()
- implement syscall_nr_to_meta() which provides the syscalls metadata
giving the syscall number

The latter callback is fast on x86-64, a table is built once the syscall
tracing is first launched. This table contains the address of each syscalls
metadata having the syscall number as an index on the table.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/ftrace.h | 7 ++++
arch/x86/include/asm/thread_info.h | 9 +++--
arch/x86/kernel/ftrace.c | 63 ++++++++++++++++++++++++++++++++++++
arch/x86/kernel/ptrace.c | 7 ++++
5 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 15ec8a2..4c6e422 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -35,6 +35,7 @@ config X86
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACE_MCOUNT_TEST
select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
+ select HAVE_FTRACE_SYSCALLS if X86_64
select HAVE_KVM
select HAVE_ARCH_KGDB
select HAVE_ARCH_TRACEHOOK
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index db24c22..d0954f7 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -28,6 +28,13 @@

#endif

+/* FIXME: I don't want to stay hardcoded */
+#ifdef CONFIG_X86_64
+#define FTRACE_SYSCALL_MAX 296
+#else
+#define FTRACE_SYSCALL_MAX 333
+#endif
+
#ifdef CONFIG_FUNCTION_TRACER
#define MCOUNT_ADDR ((long)(mcount))
#define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index f6ba6f8..83d2b73 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -95,6 +95,7 @@ struct thread_info {
#define TIF_FORCED_TF 24 /* true if TF in eflags artificially */
#define TIF_DEBUGCTLMSR 25 /* uses thread_struct.debugctlmsr */
#define TIF_DS_AREA_MSR 26 /* uses thread_struct.ds_area_msr */
+#define TIF_SYSCALL_FTRACE 27 /* for ftrace syscall instrumentation */

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
@@ -117,15 +118,17 @@ struct thread_info {
#define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
#define _TIF_DEBUGCTLMSR (1 << TIF_DEBUGCTLMSR)
#define _TIF_DS_AREA_MSR (1 << TIF_DS_AREA_MSR)
+#define _TIF_SYSCALL_FTRACE (1 << TIF_SYSCALL_FTRACE)

/* work to do in syscall_trace_enter() */
#define _TIF_WORK_SYSCALL_ENTRY \
- (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | \
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_FTRACE | \
_TIF_SYSCALL_AUDIT | _TIF_SECCOMP | _TIF_SINGLESTEP)

/* work to do in syscall_trace_leave() */
#define _TIF_WORK_SYSCALL_EXIT \
- (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP)
+ (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP | \
+ _TIF_SYSCALL_FTRACE)

/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \
@@ -134,7 +137,7 @@ struct thread_info {
_TIF_SINGLESTEP|_TIF_SECCOMP|_TIF_SYSCALL_EMU))

/* work to do on any return to user space */
-#define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)
+#define _TIF_ALLWORK_MASK ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_FTRACE)

/* Only used for 64 bit */
#define _TIF_DO_NOTIFY_MASK \
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index a85da17..1d0d7f4 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -453,3 +453,66 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#ifdef CONFIG_FTRACE_SYSCALLS
+
+extern unsigned long __start_syscalls_metadata[];
+extern unsigned long __stop_syscalls_metadata[];
+extern unsigned long *sys_call_table;
+
+static struct syscall_metadata **syscalls_metadata;
+
+static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
+{
+ struct syscall_metadata *start;
+ struct syscall_metadata *stop;
+ char str[KSYM_SYMBOL_LEN];
+
+
+ start = (struct syscall_metadata *)__start_syscalls_metadata;
+ stop = (struct syscall_metadata *)__stop_syscalls_metadata;
+ kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
+
+ for ( ; start < stop; start++) {
+ if (start->name && !strcmp(start->name, str))
+ return start;
+ }
+ return NULL;
+}
+
+struct syscall_metadata *syscall_nr_to_meta(int nr)
+{
+ if (!syscalls_metadata || nr >= FTRACE_SYSCALL_MAX || nr < 0)
+ return NULL;
+
+ return syscalls_metadata[nr];
+}
+
+void arch_init_ftrace_syscalls(void)
+{
+ int i;
+ struct syscall_metadata *meta;
+ unsigned long **psys_syscall_table = &sys_call_table;
+ static atomic_t refs;
+
+ if (atomic_inc_return(&refs) != 1)
+ goto end;
+
+ syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
+ FTRACE_SYSCALL_MAX, GFP_KERNEL);
+ if (!syscalls_metadata) {
+ WARN_ON(1);
+ return;
+ }
+
+ for (i = 0; i < FTRACE_SYSCALL_MAX; i++) {
+ meta = find_syscall_meta(psys_syscall_table[i]);
+ syscalls_metadata[i] = meta;
+ }
+ return;
+
+ /* Paranoid: avoid overflow */
+end:
+ atomic_dec(&refs);
+}
+#endif
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 3d9672e..99749d6 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -21,6 +21,7 @@
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/signal.h>
+#include <linux/ftrace.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -1416,6 +1417,9 @@ asmregparm long syscall_trace_enter(struct pt_regs *regs)
tracehook_report_syscall_entry(regs))
ret = -1L;

+ if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
+ ftrace_syscall_enter(regs);
+
if (unlikely(current->audit_context)) {
if (IS_IA32)
audit_syscall_entry(AUDIT_ARCH_I386,
@@ -1439,6 +1443,9 @@ asmregparm void syscall_trace_leave(struct pt_regs *regs)
if (unlikely(current->audit_context))
audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);

+ if (unlikely(test_thread_flag(TIF_SYSCALL_FTRACE)))
+ ftrace_syscall_exit(regs);
+
if (test_thread_flag(TIF_SYSCALL_TRACE))
tracehook_report_syscall_exit(regs, 0);

--
1.6.1