Linus,

please pull the latest x86/build branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-build-2024-09-17

up to:  ae94b263f5f6: x86: Ignore stack unwinding in KCOV

Updates for KCOV instrumentation on x86:

  - Prevent spurious KCOV coverage in common_interrupt()

  - Fixup the KCOV Makefile directive which got stale due to a source file
    rename

  - Exclude stack unwinding from KCOV as it creates large amounts of
    uninteresting coverage

  - Provide a self test to validate that KCOV coverage of the interrupt
    handling code starts not before preempt count got updated.

Thanks,

	tglx

------------------>
Dmitry Vyukov (4):
      x86/entry: Remove unwanted instrumentation in common_interrupt()
      kcov: Add interrupt handling self test
      module: Fix KCOV-ignored file name
      x86: Ignore stack unwinding in KCOV


 arch/x86/include/asm/hardirq.h  |  8 ++++++--
 arch/x86/include/asm/idtentry.h |  6 +++---
 arch/x86/kernel/Makefile        |  8 ++++++++
 kernel/kcov.c                   | 31 +++++++++++++++++++++++++++++++
 kernel/module/Makefile          |  2 +-
 lib/Kconfig.debug               |  8 ++++++++
 6 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index c67fa6ad098a..6ffa8b75f4cd 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -69,7 +69,11 @@ extern u64 arch_irq_stat(void);
 #define local_softirq_pending_ref       pcpu_hot.softirq_pending
 
 #if IS_ENABLED(CONFIG_KVM_INTEL)
-static inline void kvm_set_cpu_l1tf_flush_l1d(void)
+/*
+ * This function is called from noinstr interrupt contexts
+ * and must be inlined to not get instrumentation.
+ */
+static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void)
 {
 	__this_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 1);
 }
@@ -84,7 +88,7 @@ static __always_inline bool kvm_get_cpu_l1tf_flush_l1d(void)
 	return __this_cpu_read(irq_stat.kvm_cpu_l1tf_flush_l1d);
 }
 #else /* !IS_ENABLED(CONFIG_KVM_INTEL) */
-static inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
+static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
 #endif /* IS_ENABLED(CONFIG_KVM_INTEL) */
 
 #endif /* _ASM_X86_HARDIRQ_H */
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index d4f24499b256..ad5c68f0509d 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -212,8 +212,8 @@ __visible noinstr void func(struct pt_regs *regs,			\
 	irqentry_state_t state = irqentry_enter(regs);			\
 	u32 vector = (u32)(u8)error_code;				\
 									\
+	kvm_set_cpu_l1tf_flush_l1d();                                   \
 	instrumentation_begin();					\
-	kvm_set_cpu_l1tf_flush_l1d();					\
 	run_irq_on_irqstack_cond(__##func, regs, vector);		\
 	instrumentation_end();						\
 	irqentry_exit(regs, state);					\
@@ -250,7 +250,6 @@ static void __##func(struct pt_regs *regs);				\
 									\
 static __always_inline void instr_##func(struct pt_regs *regs)		\
 {									\
-	kvm_set_cpu_l1tf_flush_l1d();					\
 	run_sysvec_on_irqstack_cond(__##func, regs);			\
 }									\
 									\
@@ -258,6 +257,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
 {									\
 	irqentry_state_t state = irqentry_enter(regs);			\
 									\
+	kvm_set_cpu_l1tf_flush_l1d();                                   \
 	instrumentation_begin();					\
 	instr_##func (regs);						\
 	instrumentation_end();						\
@@ -288,7 +288,6 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 static __always_inline void instr_##func(struct pt_regs *regs)		\
 {									\
 	__irq_enter_raw();						\
-	kvm_set_cpu_l1tf_flush_l1d();					\
 	__##func (regs);						\
 	__irq_exit_raw();						\
 }									\
@@ -297,6 +296,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
 {									\
 	irqentry_state_t state = irqentry_enter(regs);			\
 									\
+	kvm_set_cpu_l1tf_flush_l1d();                                   \
 	instrumentation_begin();					\
 	instr_##func (regs);						\
 	instrumentation_end();						\
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a847180836e4..f7918980667a 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -35,6 +35,14 @@ KMSAN_SANITIZE_nmi.o					:= n
 # If instrumentation of the following files is enabled, boot hangs during
 # first second.
 KCOV_INSTRUMENT_head$(BITS).o				:= n
+# These are called from save_stack_trace() on debug paths,
+# and produce large amounts of uninteresting coverage.
+KCOV_INSTRUMENT_stacktrace.o				:= n
+KCOV_INSTRUMENT_dumpstack.o				:= n
+KCOV_INSTRUMENT_dumpstack_$(BITS).o			:= n
+KCOV_INSTRUMENT_unwind_orc.o				:= n
+KCOV_INSTRUMENT_unwind_frame.o				:= n
+KCOV_INSTRUMENT_unwind_guess.o				:= n
 
 CFLAGS_irq.o := -I $(src)/../include/asm/trace
 
diff --git a/kernel/kcov.c b/kernel/kcov.c
index f0a69d402066..d9d4a0c04185 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -11,6 +11,7 @@
 #include <linux/fs.h>
 #include <linux/hashtable.h>
 #include <linux/init.h>
+#include <linux/jiffies.h>
 #include <linux/kmsan-checks.h>
 #include <linux/mm.h>
 #include <linux/preempt.h>
@@ -1058,6 +1059,32 @@ u64 kcov_common_handle(void)
 }
 EXPORT_SYMBOL(kcov_common_handle);
 
+#ifdef CONFIG_KCOV_SELFTEST
+static void __init selftest(void)
+{
+	unsigned long start;
+
+	pr_err("running self test\n");
+	/*
+	 * Test that interrupts don't produce spurious coverage.
+	 * The coverage callback filters out interrupt code, but only
+	 * after the handler updates preempt count. Some code periodically
+	 * leaks out of that section and leads to spurious coverage.
+	 * It's hard to call the actual interrupt handler directly,
+	 * so we just loop here for a bit waiting for a timer interrupt.
+	 * We set kcov_mode to enable tracing, but don't setup the area,
+	 * so any attempt to trace will crash. Note: we must not call any
+	 * potentially traced functions in this region.
+	 */
+	start = jiffies;
+	current->kcov_mode = KCOV_MODE_TRACE_PC;
+	while ((jiffies - start) * MSEC_PER_SEC / HZ < 300)
+		;
+	current->kcov_mode = 0;
+	pr_err("done running self test\n");
+}
+#endif
+
 static int __init kcov_init(void)
 {
 	int cpu;
@@ -1077,6 +1104,10 @@ static int __init kcov_init(void)
 	 */
 	debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
 
+#ifdef CONFIG_KCOV_SELFTEST
+	selftest();
+#endif
+
 	return 0;
 }
 
diff --git a/kernel/module/Makefile b/kernel/module/Makefile
index a10b2b9a6fdf..50ffcc413b54 100644
--- a/kernel/module/Makefile
+++ b/kernel/module/Makefile
@@ -5,7 +5,7 @@
 
 # These are called from save_stack_trace() on slub debug path,
 # and produce insane amounts of uninteresting coverage.
-KCOV_INSTRUMENT_module.o := n
+KCOV_INSTRUMENT_main.o := n
 
 obj-y += main.o
 obj-y += strict_rwx.o
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a30c03a66172..270e367b3e6f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2173,6 +2173,14 @@ config KCOV_IRQ_AREA_SIZE
 	  soft interrupts. This specifies the size of those areas in the
 	  number of unsigned long words.
 
+config KCOV_SELFTEST
+	bool "Perform short selftests on boot"
+	depends on KCOV
+	help
+	  Run short KCOV coverage collection selftests on boot.
+	  On test failure, causes the kernel to panic. Recommended to be
+	  enabled, ensuring critical functionality works as intended.
+
 menuconfig RUNTIME_TESTING_MENU
 	bool "Runtime Testing"
 	default y

The pull request you sent on Tue, 17 Sep 2024 10:54:05 +0200 (CEST):

> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-build-2024-09-17

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/5ba202a7c986fc58dd2fd1571c99667ab2699995

Thank you!

-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/prtracker.html