tracing/uprobes: Add @+file_offset fetch method

Enable to fetch data from a file offset.  Currently it only supports
fetching from same binary uprobe set.  It'll translate the file offset
to a proper virtual address in the process.

The syntax is "@+OFFSET" as it does similar to normal memory fetching
(@ADDR) which does no address translation.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

4 files changed, 62 insertions, 1 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index f94a56915e69..ce0ed8afb77e 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -239,6 +239,14 @@ DEFINE_BASIC_FETCH_FUNCS(symbol)
 DEFINE_FETCH_symbol(string)
 DEFINE_FETCH_symbol(string_size)
 
+/* kprobes don't support file_offset fetch methods */
+#define fetch_file_offset_u8            NULL
+#define fetch_file_offset_u16           NULL
+#define fetch_file_offset_u32           NULL
+#define fetch_file_offset_u64           NULL
+#define fetch_file_offset_string        NULL
+#define fetch_file_offset_string_size   NULL
+
 /* Fetch type information table */
 const struct fetch_type kprobes_fetch_type_table[] = {
         /* Special types */
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index a130d612e705..8364a421b4df 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -374,7 +374,7 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
                 }
                 break;
 
-        case '@':       /* memory or symbol */
+        case '@':       /* memory, file-offset or symbol */
                 if (isdigit(arg[1])) {
                         ret = kstrtoul(arg + 1, 0, &param);
                         if (ret)
@@ -382,6 +382,17 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
 
                         f->fn = t->fetch[FETCH_MTD_memory];
                         f->data = (void *)param;
+                } else if (arg[1] == '+') {
+                        /* kprobes don't support file offsets */
+                        if (is_kprobe)
+                                return -EINVAL;
+
+                        ret = kstrtol(arg + 2, 0, &offset);
+                        if (ret)
+                                break;
+
+                        f->fn = t->fetch[FETCH_MTD_file_offset];
+                        f->data = (void *)offset;
                 } else {
                         /* uprobes don't support symbols */
                         if (!is_kprobe)
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 2d5b8f5f5310..e29d743fef5d 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -106,6 +106,7 @@ enum {
         FETCH_MTD_symbol,
         FETCH_MTD_deref,
         FETCH_MTD_bitfield,
+        FETCH_MTD_file_offset,
         FETCH_MTD_END,
 };
 
@@ -217,6 +218,7 @@ ASSIGN_FETCH_FUNC(memory, ftype),			\
 ASSIGN_FETCH_FUNC(symbol, ftype),                       \
 ASSIGN_FETCH_FUNC(deref, ftype),                        \
 ASSIGN_FETCH_FUNC(bitfield, ftype),                     \
+ASSIGN_FETCH_FUNC(file_offset, ftype),                  \
           }                                             \
         }
 
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 794e8bc171f3..1fdea6d3f851 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -70,6 +70,11 @@ static int unregister_uprobe_event(struct trace_uprobe *tu);
 static DEFINE_MUTEX(uprobe_lock);
 static LIST_HEAD(uprobe_list);
 
+struct uprobe_dispatch_data {
+        struct trace_uprobe     *tu;
+        unsigned long           bp_addr;
+};
+
 static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs);
 static int uretprobe_dispatcher(struct uprobe_consumer *con,
                                 unsigned long func, struct pt_regs *regs);
@@ -175,6 +180,29 @@ static __kprobes void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
 #define fetch_symbol_string             NULL
 #define fetch_symbol_string_size        NULL
 
+static unsigned long translate_user_vaddr(void *file_offset)
+{
+        unsigned long base_addr;
+        struct uprobe_dispatch_data *udd;
+
+        udd = (void *) current->utask->vaddr;
+
+        base_addr = udd->bp_addr - udd->tu->offset;
+        return base_addr + (unsigned long)file_offset;
+}
+
+#define DEFINE_FETCH_file_offset(type)                                  \
+static __kprobes void FETCH_FUNC_NAME(file_offset, type)(struct pt_regs *regs,\
+                                        void *offset, void *dest)       \
+{                                                                       \
+        void *vaddr = (void *)translate_user_vaddr(offset);             \
+                                                                        \
+        FETCH_FUNC_NAME(memory, type)(regs, vaddr, dest);               \
+}
+DEFINE_BASIC_FETCH_FUNCS(file_offset)
+DEFINE_FETCH_file_offset(string)
+DEFINE_FETCH_file_offset(string_size)
+
 /* Fetch type information table */
 const struct fetch_type uprobes_fetch_type_table[] = {
         /* Special types */
@@ -1106,11 +1134,17 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
 static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
 {
         struct trace_uprobe *tu;
+        struct uprobe_dispatch_data udd;
         int ret = 0;
 
         tu = container_of(con, struct trace_uprobe, consumer);
         tu->nhit++;
 
+        udd.tu = tu;
+        udd.bp_addr = instruction_pointer(regs);
+
+        current->utask->vaddr = (unsigned long) &udd;
+
         if (tu->tp.flags & TP_FLAG_TRACE)
                 ret |= uprobe_trace_func(tu, regs);
 
@@ -1125,9 +1159,15 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con,
                                 unsigned long func, struct pt_regs *regs)
 {
         struct trace_uprobe *tu;
+        struct uprobe_dispatch_data udd;
 
         tu = container_of(con, struct trace_uprobe, consumer);
 
+        udd.tu = tu;
+        udd.bp_addr = func;
+
+        current->utask->vaddr = (unsigned long) &udd;
+
         if (tu->tp.flags & TP_FLAG_TRACE)
                 uretprobe_trace_func(tu, func, regs);