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Message-ID: <172656198283.2471820.288980349418658549.tglx@xen13>
Date: Tue, 17 Sep 2024 10:54:05 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] x86/build for v6.12-rc1
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
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