Probes fixes for v6.7-rc1:

- Documentation update: Add a note about argument and return value
    fetching is the best effort because it depends on the type.
 
  - objpool: Fix to make internal global variables static in
    test_objpool.c.
 
  - kprobes: Unify kprobes_exceptions_nofify() prototypes. There are
    the same prototypes in asm/kprobes.h for some architectures, but
    some of them are missing the prototype and it causes a warning.
    So move the prototype into linux/kprobes.h.
 
  - tracing: Fix to check the tracepoint event and return event at
    parsing stage. The tracepoint event doesn't support %return
    but if $retval exists, it will be converted to %return silently.
    This finds that case and rejects it.
 
  - tracing: Fix the order of the descriptions about the parameters
    of __kprobe_event_gen_cmd_start() to be consistent with the
    argument list of the function.
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Merge tag 'probes-fixes-v6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull probes fixes from Masami Hiramatsu:

 - Documentation update: Add a note about argument and return value
   fetching is the best effort because it depends on the type.

 - objpool: Fix to make internal global variables static in
   test_objpool.c.

 - kprobes: Unify kprobes_exceptions_nofify() prototypes. There are the
   same prototypes in asm/kprobes.h for some architectures, but some of
   them are missing the prototype and it causes a warning. So move the
   prototype into linux/kprobes.h.

 - tracing: Fix to check the tracepoint event and return event at
   parsing stage. The tracepoint event doesn't support %return but if
   $retval exists, it will be converted to %return silently. This finds
   that case and rejects it.

 - tracing: Fix the order of the descriptions about the parameters of
   __kprobe_event_gen_cmd_start() to be consistent with the argument
   list of the function.

* tag 'probes-fixes-v6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/kprobes: Fix the order of argument descriptions
  tracing: fprobe-event: Fix to check tracepoint event and return
  kprobes: unify kprobes_exceptions_nofify() prototypes
  lib: test_objpool: make global variables static
  Documentation: tracing: Add a note about argument and retval access

Documentation/trace/fprobetrace.rst

@@ -59,8 +59,12 @@ Synopsis of fprobe-events
                   and bitfield are supported.
 
   (\*1) This is available only when BTF is enabled.
-  (\*2) only for the probe on function entry (offs == 0).
+  (\*2) only for the probe on function entry (offs == 0). Note, this argument access
-  (\*3) only for return probe.
+        is best effort, because depending on the argument type, it may be passed on
+        the stack. But this only support the arguments via registers.
+  (\*3) only for return probe. Note that this is also best effort. Depending on the
+        return value type, it might be passed via a pair of registers. But this only
+        accesses one register.
   (\*4) this is useful for fetching a field of data structures.
   (\*5) "u" means user-space dereference.
 

Documentation/trace/kprobetrace.rst

@@ -61,8 +61,12 @@ Synopsis of kprobe_events
 		  (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr"
                   and bitfield are supported.
 
-  (\*1) only for the probe on function entry (offs == 0).
+  (\*1) only for the probe on function entry (offs == 0). Note, this argument access
-  (\*2) only for return probe.
+        is best effort, because depending on the argument type, it may be passed on
+        the stack. But this only support the arguments via registers.
+  (\*2) only for return probe. Note that this is also best effort. Depending on the
+        return value type, it might be passed via a pair of registers. But this only
+        accesses one register.
   (\*3) this is useful for fetching a field of data structures.
   (\*4) "u" means user-space dereference. See :ref:`user_mem_access`.
 

arch/arc/include/asm/kprobes.h

@@ -32,9 +32,6 @@ struct kprobe;
 
 void arch_remove_kprobe(struct kprobe *p);
 
-int kprobe_exceptions_notify(struct notifier_block *self,
-			     unsigned long val, void *data);
-
 struct prev_kprobe {
 	struct kprobe *kp;
 	unsigned long status;

arch/arm/include/asm/kprobes.h

@@ -40,8 +40,6 @@ struct kprobe_ctlblk {
 
 void arch_remove_kprobe(struct kprobe *);
 int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
-int kprobe_exceptions_notify(struct notifier_block *self,
-			     unsigned long val, void *data);
 
 /* optinsn template addresses */
 extern __visible kprobe_opcode_t optprobe_template_entry[];

arch/arm64/include/asm/kprobes.h

@@ -37,8 +37,6 @@ struct kprobe_ctlblk {
 
 void arch_remove_kprobe(struct kprobe *);
 int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
-int kprobe_exceptions_notify(struct notifier_block *self,
-			     unsigned long val, void *data);
 void __kretprobe_trampoline(void);
 void __kprobes *trampoline_probe_handler(struct pt_regs *regs);
 

arch/mips/include/asm/kprobes.h

@@ -71,8 +71,6 @@ struct kprobe_ctlblk {
 	struct prev_kprobe prev_kprobe;
 };
 
-extern int kprobe_exceptions_notify(struct notifier_block *self,
-				    unsigned long val, void *data);
 
 #endif /* CONFIG_KPROBES */
 #endif /* _ASM_KPROBES_H */

arch/powerpc/include/asm/kprobes.h

@@ -84,8 +84,6 @@ struct arch_optimized_insn {
 	kprobe_opcode_t *insn;
 };
 
-extern int kprobe_exceptions_notify(struct notifier_block *self,
-					unsigned long val, void *data);
 extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
 extern int kprobe_handler(struct pt_regs *regs);
 extern int kprobe_post_handler(struct pt_regs *regs);

arch/s390/include/asm/kprobes.h

@@ -73,8 +73,6 @@ struct kprobe_ctlblk {
 void arch_remove_kprobe(struct kprobe *p);
 
 int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
-int kprobe_exceptions_notify(struct notifier_block *self,
-	unsigned long val, void *data);
 
 #define flush_insn_slot(p)	do { } while (0)
 

arch/sh/include/asm/kprobes.h

@@ -46,8 +46,6 @@ struct kprobe_ctlblk {
 };
 
 extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
-extern int kprobe_exceptions_notify(struct notifier_block *self,
-				    unsigned long val, void *data);
 extern int kprobe_handle_illslot(unsigned long pc);
 #else
 

arch/sparc/include/asm/kprobes.h

@@ -47,8 +47,6 @@ struct kprobe_ctlblk {
 	struct prev_kprobe prev_kprobe;
 };
 
-int kprobe_exceptions_notify(struct notifier_block *self,
-			     unsigned long val, void *data);
 int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 				      struct pt_regs *regs);

arch/x86/include/asm/kprobes.h

@@ -113,8 +113,6 @@ struct kprobe_ctlblk {
 };
 
 extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
-extern int kprobe_exceptions_notify(struct notifier_block *self,
-				    unsigned long val, void *data);
 extern int kprobe_int3_handler(struct pt_regs *regs);
 
 #else

include/linux/kprobes.h

@@ -445,6 +445,10 @@ int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 
 int arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
 			    char *type, char *sym);
+
+int kprobe_exceptions_notify(struct notifier_block *self,
+			     unsigned long val, void *data);
+
 #else /* !CONFIG_KPROBES: */
 
 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)

kernel/trace/trace_fprobe.c

@@ -927,11 +927,12 @@ static int parse_symbol_and_return(int argc, const char *argv[],
 	for (i = 2; i < argc; i++) {
 		tmp = strstr(argv[i], "$retval");
 		if (tmp && !isalnum(tmp[7]) && tmp[7] != '_') {
+			if (is_tracepoint) {
+				trace_probe_log_set_index(i);
+				trace_probe_log_err(tmp - argv[i], RETVAL_ON_PROBE);
+				return -EINVAL;
+			}
 			*is_return = true;
-			/*
-			 * NOTE: Don't check is_tracepoint here, because it will
-			 * be checked when the argument is parsed.
-			 */
 			break;
 		}
 	}

kernel/trace/trace_kprobe.c

@@ -1020,9 +1020,9 @@ EXPORT_SYMBOL_GPL(kprobe_event_cmd_init);
 /**
  * __kprobe_event_gen_cmd_start - Generate a kprobe event command from arg list
  * @cmd: A pointer to the dynevent_cmd struct representing the new event
+ * @kretprobe: Is this a return probe?
  * @name: The name of the kprobe event
  * @loc: The location of the kprobe event
- * @kretprobe: Is this a return probe?
  * @...: Variable number of arg (pairs), one pair for each field
  *
  * NOTE: Users normally won't want to call this function directly, but

lib/test_objpool.c

@@ -311,7 +311,7 @@ static void ot_fini_sync(struct ot_context *sop)
 	ot_kfree(sop->test, sop, sizeof(*sop));
 }
 
-struct {
+static struct {
 	struct ot_context * (*init)(struct ot_test *oc);
 	void (*fini)(struct ot_context *sop);
 } g_ot_sync_ops[] = {
@@ -475,7 +475,7 @@ static struct ot_context *ot_init_async_m0(struct ot_test *test)
 	return sop;
 }
 
-struct {
+static struct {
 	struct ot_context * (*init)(struct ot_test *oc);
 	void (*fini)(struct ot_context *sop);
 } g_ot_async_ops[] = {
@@ -632,7 +632,7 @@ static int ot_start_async(struct ot_test *test)
 #define NODE_COMPACT sizeof(struct ot_node)
 #define NODE_VMALLOC (512)
 
-struct ot_test g_testcases[] = {
+static struct ot_test g_testcases[] = {
 
 	/* sync & normal */
 	{0, 0, NODE_COMPACT, 1000, 0,  1,  0,  0, "sync: percpu objpool"},