Merge tag 'trace-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - kprobes: Restructured stack unwinder to show properly on x86 when a
   stack dump happens from a kretprobe callback.

 - Fix to bootconfig parsing

 - Have tracefs allow owner and group permissions by default (only
   denying others). There's been pressure to allow non root to tracefs
   in a controlled fashion, and using groups is probably the safest.

 - Bootconfig memory managament updates.

 - Bootconfig clean up to have the tools directory be less dependent on
   changes in the kernel tree.

 - Allow perf to be traced by function tracer.

 - Rewrite of function graph tracer to be a callback from the function
   tracer instead of having its own trampoline (this change will happen
   on an arch by arch basis, and currently only x86_64 implements it).

 - Allow multiple direct trampolines (bpf hooks to functions) be batched
   together in one synchronization.

 - Allow histogram triggers to add variables that can perform
   calculations against the event's fields.

 - Use the linker to determine architecture callbacks from the ftrace
   trampoline to allow for proper parameter prototypes and prevent
   warnings from the compiler.

 - Extend histogram triggers to key off of variables.

 - Have trace recursion use bit magic to determine preempt context over
   if branches.

 - Have trace recursion disable preemption as all use cases do anyway.

 - Added testing for verification of tracing utilities.

 - Various small clean ups and fixes.

* tag 'trace-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (101 commits)
  tracing/histogram: Fix semicolon.cocci warnings
  tracing/histogram: Fix documentation inline emphasis warning
  tracing: Increase PERF_MAX_TRACE_SIZE to handle Sentinel1 and docker together
  tracing: Show size of requested perf buffer
  bootconfig: Initialize ret in xbc_parse_tree()
  ftrace: do CPU checking after preemption disabled
  ftrace: disable preemption when recursion locked
  tracing/histogram: Document expression arithmetic and constants
  tracing/histogram: Optimize division by a power of 2
  tracing/histogram: Covert expr to const if both operands are constants
  tracing/histogram: Simplify handling of .sym-offset in expressions
  tracing: Fix operator precedence for hist triggers expression
  tracing: Add division and multiplication support for hist triggers
  tracing: Add support for creating hist trigger variables from literal
  selftests/ftrace: Stop tracing while reading the trace file by default
  MAINTAINERS: Update KPROBES and TRACING entries
  test_kprobes: Move it from kernel/ to lib/
  docs, kprobes: Remove invalid URL and add new reference
  samples/kretprobes: Fix return value if register_kretprobe() failed
  lib/bootconfig: Fix the xbc_get_info kerneldoc
  ...

1 files changed, 33 insertions, 10 deletions

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 9d8634e2f12f..9090c3a74dcc 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -11,6 +11,8 @@
  * Copyright (C) 2007 Marvell Ltd.
  */
 
+#define pr_fmt(fmt) "kprobes: " fmt
+
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
 #include <linux/module.h>
@@ -278,7 +280,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
 				break;
 			case KPROBE_REENTER:
 				/* A nested probe was hit in FIQ, it is a BUG */
-				pr_warn("Unrecoverable kprobe detected.\n");
+				pr_warn("Failed to recover from reentered kprobes.\n");
 				dump_kprobe(p);
 				fallthrough;
 			default:
@@ -366,19 +368,41 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 /*
  * When a retprobed function returns, trampoline_handler() is called,
  * calling the kretprobe's handler. We construct a struct pt_regs to
- * give a view of registers r0-r11 to the user return-handler.  This is
- * not a complete pt_regs structure, but that should be plenty sufficient
- * for kretprobe handlers which should normally be interested in r0 only
- * anyway.
+ * give a view of registers r0-r11, sp, lr, and pc to the user
+ * return-handler. This is not a complete pt_regs structure, but that
+ * should be enough for stacktrace from the return handler with or
+ * without pt_regs.
  */
-void __naked __kprobes kretprobe_trampoline(void)
+void __naked __kprobes __kretprobe_trampoline(void)
 {
 	__asm__ __volatile__ (
+#ifdef CONFIG_FRAME_POINTER
+		"ldr	lr, =__kretprobe_trampoline	\n\t"
+	/* __kretprobe_trampoline makes a framepointer on pt_regs. */
+#ifdef CONFIG_CC_IS_CLANG
+		"stmdb	sp, {sp, lr, pc}	\n\t"
+		"sub	sp, sp, #12		\n\t"
+		/* In clang case, pt_regs->ip = lr. */
+		"stmdb	sp!, {r0 - r11, lr}	\n\t"
+		/* fp points regs->r11 (fp) */
+		"add	fp, sp,	#44		\n\t"
+#else /* !CONFIG_CC_IS_CLANG */
+		/* In gcc case, pt_regs->ip = fp. */
+		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
+		"sub	sp, sp, #16		\n\t"
+		"stmdb	sp!, {r0 - r11}		\n\t"
+		/* fp points regs->r15 (pc) */
+		"add	fp, sp, #60		\n\t"
+#endif /* CONFIG_CC_IS_CLANG */
+#else /* !CONFIG_FRAME_POINTER */
+		"sub	sp, sp, #16		\n\t"
 		"stmdb	sp!, {r0 - r11}		\n\t"
+#endif /* CONFIG_FRAME_POINTER */
 		"mov	r0, sp			\n\t"
 		"bl	trampoline_handler	\n\t"
 		"mov	lr, r0			\n\t"
 		"ldmia	sp!, {r0 - r11}		\n\t"
+		"add	sp, sp, #16		\n\t"
 #ifdef CONFIG_THUMB2_KERNEL
 		"bx	lr			\n\t"
 #else
@@ -387,11 +411,10 @@ void __naked __kprobes kretprobe_trampoline(void)
 		: : : "memory");
 }
 
-/* Called from kretprobe_trampoline */
+/* Called from __kretprobe_trampoline */
 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 {
-	return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline,
-						    (void *)regs->ARM_fp);
+	return (void *)kretprobe_trampoline_handler(regs, (void *)regs->ARM_fp);
 }
 
 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
@@ -401,7 +424,7 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 	ri->fp = (void *)regs->ARM_fp;
 
 	/* Replace the return addr with trampoline addr. */
-	regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
+	regs->ARM_lr = (unsigned long)&__kretprobe_trampoline;
 }
 
 int __kprobes arch_trampoline_kprobe(struct kprobe *p)