probes updates for 6.3:

- Skip negative return code check for snprintf in eprobe.
 
 - Add recursive call test cases for kprobe unit test
 
 - Add 'char' type to probe events to show it as the character instead of value.
 
 - Update kselftest kprobe-event testcase to ignore '__pfx_' symbols.
 
 - Fix kselftest to check filter on eprobe event correctly.
 
 - Add filter on eprobe to the README file in tracefs.
 
 - Fix optprobes to check whether there is 'under unoptimizing' optprobe when optimizing another kprobe correctly.
 
 - Fix optprobe to check whether there is 'under unoptimizing' optprobe when fetching the original instruction correctly.
 
 - Fix optprobe to free 'forcibly unoptimized' optprobe correctly.
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Merge tag 'probes-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull kprobes updates from Masami Hiramatsu:

 - Skip negative return code check for snprintf in eprobe

 - Add recursive call test cases for kprobe unit test

 - Add 'char' type to probe events to show it as the character instead
   of value

 - Update kselftest kprobe-event testcase to ignore '__pfx_' symbols

 - Fix kselftest to check filter on eprobe event correctly

 - Add filter on eprobe to the README file in tracefs

 - Fix optprobes to check whether there is 'under unoptimizing' optprobe
   when optimizing another kprobe correctly

 - Fix optprobe to check whether there is 'under unoptimizing' optprobe
   when fetching the original instruction correctly

 - Fix optprobe to free 'forcibly unoptimized' optprobe correctly

* tag 'probes-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/eprobe: no need to check for negative ret value for snprintf
  test_kprobes: Add recursed kprobe test case
  tracing/probe: add a char type to show the character value of traced arguments
  selftests/ftrace: Fix probepoint testcase to ignore __pfx_* symbols
  selftests/ftrace: Fix eprobe syntax test case to check filter support
  tracing/eprobe: Fix to add filter on eprobe description in README file
  x86/kprobes: Fix arch_check_optimized_kprobe check within optimized_kprobe range
  x86/kprobes: Fix __recover_optprobed_insn check optimizing logic
  kprobes: Fix to handle forcibly unoptimized kprobes on freeing_list

Documentation/trace/kprobetrace.rst

@@ -58,7 +58,7 @@ Synopsis of kprobe_events
   NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
   FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
 		  (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
-		  (x8/x16/x32/x64), "string", "ustring", "symbol", "symstr"
+		  (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr"
                   and bitfield are supported.
 
   (\*1) only for the probe on function entry (offs == 0).
@@ -82,6 +82,8 @@ Note that the array can be applied to memory type fetchargs, you can not
 apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is
 wrong, but '+8($stack):x8[8]' is OK.)
 
+Char type can be used to show the character value of traced arguments.
+
 String type is a special type, which fetches a "null-terminated" string from
 kernel space. This means it will fail and store NULL if the string container
 has been paged out. "ustring" type is an alternative of string for user-space.

arch/x86/kernel/kprobes/opt.c

@@ -46,8 +46,8 @@ unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
 		/* This function only handles jump-optimized kprobe */
 		if (kp && kprobe_optimized(kp)) {
 			op = container_of(kp, struct optimized_kprobe, kp);
-			/* If op->list is not empty, op is under optimizing */
-			if (list_empty(&op->list))
+			/* If op is optimized or under unoptimizing */
+			if (list_empty(&op->list) || optprobe_queued_unopt(op))
 				goto found;
 		}
 	}
@@ -353,7 +353,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe *op)
 
 	for (i = 1; i < op->optinsn.size; i++) {
 		p = get_kprobe(op->kp.addr + i);
-		if (p && !kprobe_disabled(p))
+		if (p && !kprobe_disarmed(p))
 			return -EEXIST;
 	}
 

include/linux/kprobes.h

@@ -378,6 +378,8 @@ extern void opt_pre_handler(struct kprobe *p, struct pt_regs *regs);
 DEFINE_INSN_CACHE_OPS(optinsn);
 
 extern void wait_for_kprobe_optimizer(void);
+bool optprobe_queued_unopt(struct optimized_kprobe *op);
+bool kprobe_disarmed(struct kprobe *p);
 #else /* !CONFIG_OPTPROBES */
 static inline void wait_for_kprobe_optimizer(void) { }
 #endif /* CONFIG_OPTPROBES */

kernel/kprobes.c

@@ -458,7 +458,7 @@ static inline int kprobe_optready(struct kprobe *p)
 }
 
 /* Return true if the kprobe is disarmed. Note: p must be on hash list */
-static inline bool kprobe_disarmed(struct kprobe *p)
+bool kprobe_disarmed(struct kprobe *p)
 {
 	struct optimized_kprobe *op;
 
@@ -555,17 +555,15 @@ static void do_unoptimize_kprobes(void)
 	/* See comment in do_optimize_kprobes() */
 	lockdep_assert_cpus_held();
 
-	/* Unoptimization must be done anytime */
-	if (list_empty(&unoptimizing_list))
-		return;
+	if (!list_empty(&unoptimizing_list))
+		arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
 
-	arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
-	/* Loop on 'freeing_list' for disarming */
+	/* Loop on 'freeing_list' for disarming and removing from kprobe hash list */
 	list_for_each_entry_safe(op, tmp, &freeing_list, list) {
 		/* Switching from detour code to origin */
 		op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
-		/* Disarm probes if marked disabled */
-		if (kprobe_disabled(&op->kp))
+		/* Disarm probes if marked disabled and not gone */
+		if (kprobe_disabled(&op->kp) && !kprobe_gone(&op->kp))
 			arch_disarm_kprobe(&op->kp);
 		if (kprobe_unused(&op->kp)) {
 			/*
@@ -662,7 +660,7 @@ void wait_for_kprobe_optimizer(void)
 	mutex_unlock(&kprobe_mutex);
 }
 
-static bool optprobe_queued_unopt(struct optimized_kprobe *op)
+bool optprobe_queued_unopt(struct optimized_kprobe *op)
 {
 	struct optimized_kprobe *_op;
 
@@ -797,14 +795,13 @@ static void kill_optimized_kprobe(struct kprobe *p)
 	op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
 
 	if (kprobe_unused(p)) {
-		/* Enqueue if it is unused */
-		list_add(&op->list, &freeing_list);
 		/*
-		 * Remove unused probes from the hash list. After waiting
-		 * for synchronization, this probe is reclaimed.
-		 * (reclaiming is done by do_free_cleaned_kprobes().)
+		 * Unused kprobe is on unoptimizing or freeing list. We move it
+		 * to freeing_list and let the kprobe_optimizer() remove it from
+		 * the kprobe hash list and free it.
 		 */
-		hlist_del_rcu(&op->kp.hlist);
+		if (optprobe_queued_unopt(op))
+			list_move(&op->list, &freeing_list);
 	}
 
 	/* Don't touch the code, because it is already freed. */

kernel/trace/trace.c

@@ -5646,7 +5646,7 @@ static const char readme_msg[] =
 #ifdef CONFIG_HIST_TRIGGERS
 	"\t           s:[synthetic/]<event> <field> [<field>]\n"
 #endif
-	"\t           e[:[<group>/][<event>]] <attached-group>.<attached-event> [<args>]\n"
+	"\t           e[:[<group>/][<event>]] <attached-group>.<attached-event> [<args>] [if <filter>]\n"
 	"\t           -:[<group>/][<event>]\n"
 #ifdef CONFIG_KPROBE_EVENTS
 	"\t    place: [<module>:]<symbol>[+<offset>]|<memaddr>\n"
@@ -5663,7 +5663,7 @@ static const char readme_msg[] =
 	"\t           $stack<index>, $stack, $retval, $comm,\n"
 #endif
 	"\t           +|-[u]<offset>(<fetcharg>), \\imm-value, \\\"imm-string\"\n"
-	"\t     type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
+	"\t     type: s8/16/32/64, u8/16/32/64, x8/16/32/64, char, string, symbol,\n"
 	"\t           b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
 	"\t           symstr, <type>\\[<array-size>\\]\n"
 #ifdef CONFIG_HIST_TRIGGERS

kernel/trace/trace_eprobe.c

@@ -923,17 +923,13 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch
 
 	p = ep->filter_str;
 	for (i = 0; i < argc; i++) {
-		ret = snprintf(p, len, "%s ", argv[i]);
-		if (ret < 0)
-			goto error;
-		if (ret > len) {
-			ret = -E2BIG;
-			goto error;
-		}
+		if (i)
+			ret = snprintf(p, len, " %s", argv[i]);
+		else
+			ret = snprintf(p, len, "%s", argv[i]);
 		p += ret;
 		len -= ret;
 	}
-	p[-1] = '\0';
 
 	/*
 	 * Ensure the filter string can be parsed correctly. Note, this

kernel/trace/trace_probe.c

@@ -50,6 +50,7 @@ DEFINE_BASIC_PRINT_TYPE_FUNC(x8,  u8,  "0x%x")
 DEFINE_BASIC_PRINT_TYPE_FUNC(x16, u16, "0x%x")
 DEFINE_BASIC_PRINT_TYPE_FUNC(x32, u32, "0x%x")
 DEFINE_BASIC_PRINT_TYPE_FUNC(x64, u64, "0x%Lx")
+DEFINE_BASIC_PRINT_TYPE_FUNC(char, u8, "'%c'")
 
 int PRINT_TYPE_FUNC_NAME(symbol)(struct trace_seq *s, void *data, void *ent)
 {
@@ -95,6 +96,7 @@ static const struct fetch_type probe_fetch_types[] = {
 	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
 	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
 	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
+	ASSIGN_FETCH_TYPE_ALIAS(char, u8, u8,  0),
 	ASSIGN_FETCH_TYPE_ALIAS(symbol, ADDR_FETCH_TYPE, ADDR_FETCH_TYPE, 0),
 
 	ASSIGN_FETCH_TYPE_END

kernel/trace/trace_probe.h

@@ -166,6 +166,7 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(x16);
 DECLARE_BASIC_PRINT_TYPE_FUNC(x32);
 DECLARE_BASIC_PRINT_TYPE_FUNC(x64);
 
+DECLARE_BASIC_PRINT_TYPE_FUNC(char);
 DECLARE_BASIC_PRINT_TYPE_FUNC(string);
 DECLARE_BASIC_PRINT_TYPE_FUNC(symbol);
 

lib/test_kprobes.c

@@ -14,6 +14,7 @@
 
 static u32 rand1, preh_val, posth_val;
 static u32 (*target)(u32 value);
+static u32 (*recursed_target)(u32 value);
 static u32 (*target2)(u32 value);
 static struct kunit *current_test;
 
@@ -27,18 +28,27 @@ static noinline u32 kprobe_target(u32 value)
 	return (value / div_factor);
 }
 
+static noinline u32 kprobe_recursed_target(u32 value)
+{
+	return (value / div_factor);
+}
+
 static int kp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	KUNIT_EXPECT_FALSE(current_test, preemptible());
-	preh_val = (rand1 / div_factor);
+
+	preh_val = recursed_target(rand1);
 	return 0;
 }
 
 static void kp_post_handler(struct kprobe *p, struct pt_regs *regs,
 		unsigned long flags)
 {
+	u32 expval = recursed_target(rand1);
+
 	KUNIT_EXPECT_FALSE(current_test, preemptible());
-	KUNIT_EXPECT_EQ(current_test, preh_val, (rand1 / div_factor));
+	KUNIT_EXPECT_EQ(current_test, preh_val, expval);
+
 	posth_val = preh_val + div_factor;
 }
 
@@ -136,6 +146,29 @@ static void test_kprobes(struct kunit *test)
 	unregister_kprobes(kps, 2);
 }
 
+static struct kprobe kp_missed = {
+	.symbol_name = "kprobe_recursed_target",
+	.pre_handler = kp_pre_handler,
+	.post_handler = kp_post_handler,
+};
+
+static void test_kprobe_missed(struct kunit *test)
+{
+	current_test = test;
+	preh_val = 0;
+	posth_val = 0;
+
+	KUNIT_EXPECT_EQ(test, 0, register_kprobe(&kp_missed));
+
+	recursed_target(rand1);
+
+	KUNIT_EXPECT_EQ(test, 2, kp_missed.nmissed);
+	KUNIT_EXPECT_NE(test, 0, preh_val);
+	KUNIT_EXPECT_NE(test, 0, posth_val);
+
+	unregister_kprobe(&kp_missed);
+}
+
 #ifdef CONFIG_KRETPROBES
 static u32 krph_val;
 
@@ -336,6 +369,7 @@ static int kprobes_test_init(struct kunit *test)
 {
 	target = kprobe_target;
 	target2 = kprobe_target2;
+	recursed_target = kprobe_recursed_target;
 	stacktrace_target = kprobe_stacktrace_target;
 	internal_target = kprobe_stacktrace_internal_target;
 	stacktrace_driver = kprobe_stacktrace_driver;
@@ -346,6 +380,7 @@ static int kprobes_test_init(struct kunit *test)
 static struct kunit_case kprobes_testcases[] = {
 	KUNIT_CASE(test_kprobe),
 	KUNIT_CASE(test_kprobes),
+	KUNIT_CASE(test_kprobe_missed),
 #ifdef CONFIG_KRETPROBES
 	KUNIT_CASE(test_kretprobe),
 	KUNIT_CASE(test_kretprobes),

tools/testing/selftests/ftrace/test.d/dynevent/eprobes_syntax_errors.tc

@@ -22,6 +22,8 @@ check_error 'e:foo/^bar.1 syscalls/sys_enter_openat'	# BAD_EVENT_NAME
 check_error 'e:foo/bar syscalls/sys_enter_openat arg=^dfd'	# BAD_FETCH_ARG
 check_error 'e:foo/bar syscalls/sys_enter_openat ^arg=$foo'	# BAD_ATTACH_ARG
 
-check_error 'e:foo/bar syscalls/sys_enter_openat if ^'	# NO_EP_FILTER
+if grep -q '<attached-group>\.<attached-event>.*\[if <filter>\]' README; then
+  check_error 'e:foo/bar syscalls/sys_enter_openat if ^'	# NO_EP_FILTER
+fi
 
 exit 0

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc

@@ -0,0 +1,47 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Kprobe event char type argument
+# requires: kprobe_events
+
+case `uname -m` in
+x86_64)
+  ARG1=%di
+;;
+i[3456]86)
+  ARG1=%ax
+;;
+aarch64)
+  ARG1=%x0
+;;
+arm*)
+  ARG1=%r0
+;;
+ppc64*)
+  ARG1=%r3
+;;
+ppc*)
+  ARG1=%r3
+;;
+s390*)
+  ARG1=%r2
+;;
+mips*)
+  ARG1=%r4
+;;
+*)
+  echo "Please implement other architecture here"
+  exit_untested
+esac
+
+: "Test get argument (1)"
+echo "p:testprobe tracefs_create_dir arg1=+0(${ARG1}):char" > kprobe_events
+echo 1 > events/kprobes/testprobe/enable
+echo "p:test $FUNCTION_FORK" >> kprobe_events
+grep -qe "testprobe.* arg1='t'" trace
+
+echo 0 > events/kprobes/testprobe/enable
+: "Test get argument (2)"
+echo "p:testprobe tracefs_create_dir arg1=+0(${ARG1}):char arg2=+0(${ARG1}):char[4]" > kprobe_events
+echo 1 > events/kprobes/testprobe/enable
+echo "p:test $FUNCTION_FORK" >> kprobe_events
+grep -qe "testprobe.* arg1='t' arg2={'t','e','s','t'}" trace

tools/testing/selftests/ftrace/test.d/kprobe/probepoint.tc

@@ -21,7 +21,7 @@ set_offs() { # prev target next
 
 # We have to decode symbol addresses to get correct offsets.
 # If the offset is not an instruction boundary, it cause -EILSEQ.
-set_offs `grep -A1 -B1 ${TARGET_FUNC} /proc/kallsyms | cut -f 1 -d " " | xargs`
+set_offs `grep -v __pfx_ /proc/kallsyms | grep -A1 -B1 ${TARGET_FUNC} | cut -f 1 -d " " | xargs`
 
 UINT_TEST=no
 # printf "%x" -1 returns (unsigned long)-1.