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Subject[PATCH 4/6] tracing: add tracing support for compat syscalls
Add core support to event tracing for compat syscalls. The basic idea is that we
check if we have a compat task via 'is_compat_task()'. If so, we lookup in the
new compat_syscalls_metadata table, the corresponding struct syscall_metadata, to
check syscall arguments and whether or not we are enabled.

Signed-off-by: Jason Baron <jbaron@redhat.com>
---
include/linux/compat.h | 8 +++++
include/trace/syscall.h | 4 ++
kernel/trace/trace.h | 2 +
kernel/trace/trace_syscalls.c | 63 +++++++++++++++++++++++++++++++++++-----
4 files changed, 69 insertions(+), 8 deletions(-)
diff --git a/include/linux/compat.h b/include/linux/compat.h
index ef68119..ab2cda2 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -353,5 +353,13 @@ asmlinkage long compat_sys_newfstatat(unsigned int dfd, char __user * filename,
asmlinkage long compat_sys_openat(unsigned int dfd, const char __user *filename,
int flags, int mode);

+#else /* CONFIG_COMPAT */
+
+#define NR_syscalls_compat 0
+static inline int is_compat_task(void)
+{
+ return 0;
+}
+
#endif /* CONFIG_COMPAT */
#endif /* _LINUX_COMPAT_H */
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index 8f5ac38..1cc1d1e 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -22,6 +22,7 @@
struct syscall_metadata {
const char *name;
int syscall_nr;
+ int compat_syscall_nr;
int nb_args;
const char **types;
const char **args;
@@ -36,6 +37,9 @@ struct syscall_metadata {

#ifdef CONFIG_FTRACE_SYSCALLS
extern unsigned long arch_syscall_addr(int nr);
+#ifdef CONFIG_COMPAT
+extern unsigned long arch_compat_syscall_addr(int nr);
+#endif
extern int init_syscall_trace(struct ftrace_event_call *call);

extern int syscall_enter_define_fields(struct ftrace_event_call *call);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ce077fb..0ed0d2e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -94,12 +94,14 @@ extern struct tracer boot_tracer;
struct syscall_trace_enter {
struct trace_entry ent;
int nr;
+ int compat;
unsigned long args[];
};

struct syscall_trace_exit {
struct trace_entry ent;
int nr;
+ int compat;
long ret;
};

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 8411d6c..6f721be 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -3,6 +3,7 @@
#include <linux/kernel.h>
#include <linux/ftrace.h>
#include <linux/perf_event.h>
+#include <linux/compat.h>
#include <asm/syscall.h>

#include "trace_output.h"
@@ -16,6 +17,7 @@ extern unsigned long __start_syscalls_metadata[];
extern unsigned long __stop_syscalls_metadata[];

static struct syscall_metadata **syscalls_metadata;
+static struct syscall_metadata **compat_syscalls_metadata;

static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
{
@@ -41,8 +43,14 @@ static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
return NULL;
}

-static struct syscall_metadata *syscall_nr_to_meta(int nr)
+static struct syscall_metadata *syscall_nr_to_meta(int nr, int compat)
{
+ if (compat) {
+ if (!compat_syscalls_metadata || nr >= NR_syscalls_compat ||
+ nr < 0)
+ return NULL;
+ return compat_syscalls_metadata[nr];
+ }
if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
return NULL;

@@ -60,7 +68,7 @@ print_syscall_enter(struct trace_iterator *iter, int flags)

trace = (typeof(trace))ent;
syscall = trace->nr;
- entry = syscall_nr_to_meta(syscall);
+ entry = syscall_nr_to_meta(syscall, trace->compat);

if (!entry)
goto end;
@@ -113,7 +121,7 @@ print_syscall_exit(struct trace_iterator *iter, int flags)

trace = (typeof(trace))ent;
syscall = trace->nr;
- entry = syscall_nr_to_meta(syscall);
+ entry = syscall_nr_to_meta(syscall, trace->compat);

if (!entry) {
trace_seq_printf(s, "\n");
@@ -248,12 +256,16 @@ void ftrace_syscall_enter(struct pt_regs *regs, long id)
struct ring_buffer *buffer;
int size;
int syscall_nr;
+ int compat = 0;

syscall_nr = syscall_get_nr(current, regs);
if (syscall_nr < 0)
return;

- sys_data = syscall_nr_to_meta(syscall_nr);
+ if (is_compat_task())
+ compat = 1;
+
+ sys_data = syscall_nr_to_meta(syscall_nr, compat);
if (!sys_data)
return;

@@ -269,6 +281,7 @@ void ftrace_syscall_enter(struct pt_regs *regs, long id)

entry = ring_buffer_event_data(event);
entry->nr = syscall_nr;
+ entry->compat = compat;
syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);

if (!filter_current_check_discard(buffer, sys_data->enter_event,
@@ -283,12 +296,16 @@ void ftrace_syscall_exit(struct pt_regs *regs, long ret)
struct ring_buffer_event *event;
struct ring_buffer *buffer;
int syscall_nr;
+ int compat = 0;

syscall_nr = syscall_get_nr(current, regs);
if (syscall_nr < 0)
return;

- sys_data = syscall_nr_to_meta(syscall_nr);
+ if (is_compat_task())
+ compat = 1;
+
+ sys_data = syscall_nr_to_meta(syscall_nr, compat);
if (!sys_data)
return;

@@ -302,6 +319,7 @@ void ftrace_syscall_exit(struct pt_regs *regs, long ret)

entry = ring_buffer_event_data(event);
entry->nr = syscall_nr;
+ entry->compat = compat;
entry->ret = syscall_get_return_value(current, regs);

if (!filter_current_check_discard(buffer, sys_data->exit_event,
@@ -416,7 +434,26 @@ int __init init_ftrace_syscalls(void)
meta->syscall_nr = i;
syscalls_metadata[i] = meta;
}
-
+#ifdef CONFIG_COMPAT
+ if (NR_syscalls_compat) {
+ compat_syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
+ NR_syscalls_compat, GFP_KERNEL);
+ if (!compat_syscalls_metadata) {
+ WARN_ON(1);
+ kfree(syscalls_metadata);
+ return -ENOMEM;
+ }
+ for (i = 0; i < NR_syscalls_compat; i++) {
+ addr = arch_compat_syscall_addr(i);
+ meta = find_syscall_meta(addr);
+ if (!meta)
+ continue;
+
+ meta->compat_syscall_nr = i;
+ compat_syscalls_metadata[i] = meta;
+ }
+ }
+#endif
return 0;
}
core_initcall(init_ftrace_syscalls);
@@ -434,9 +471,13 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
int syscall_nr;
int rctx;
int size;
+ int compat = 0;

syscall_nr = syscall_get_nr(current, regs);
- sys_data = syscall_nr_to_meta(syscall_nr);
+ if (is_compat_task())
+ compat = 1;
+
+ sys_data = syscall_nr_to_meta(syscall_nr, compat);
if (!sys_data)
return;

@@ -458,6 +499,7 @@ static void prof_syscall_enter(struct pt_regs *regs, long id)
return;

rec->nr = syscall_nr;
+ rec->compat = compat;
syscall_get_arguments(current, regs, 0, sys_data->nb_args,
(unsigned long *)&rec->args);
ftrace_perf_buf_submit(rec, size, rctx, 0, 1, flags);
@@ -506,9 +548,13 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
int syscall_nr;
int rctx;
int size;
+ int compat = 0;

syscall_nr = syscall_get_nr(current, regs);
- sys_data = syscall_nr_to_meta(syscall_nr);
+ if (is_compat_task())
+ compat = 1;
+
+ sys_data = syscall_nr_to_meta(syscall_nr, compat);
if (!sys_data)
return;

@@ -533,6 +579,7 @@ static void prof_syscall_exit(struct pt_regs *regs, long ret)
return;

rec->nr = syscall_nr;
+ rec->compat = compat;
rec->ret = syscall_get_return_value(current, regs);

ftrace_perf_buf_submit(rec, size, rctx, 0, 1, flags);
--
1.6.5.1


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