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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.
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Merge tag 'x86-build-2024-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 build updates from Thomas Gleixner:
"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"
* tag 'x86-build-2024-09-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86: Ignore stack unwinding in KCOV
module: Fix KCOV-ignored file name
kcov: Add interrupt handling self test
x86/entry: Remove unwanted instrumentation in common_interrupt()
This commit is contained in:
Linus Torvalds
commit
5ba202a7c9
@ -69,7 +69,11 @@ extern u64 arch_irq_stat(void);
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#define local_softirq_pending_ref pcpu_hot.softirq_pending
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#if IS_ENABLED(CONFIG_KVM_INTEL)
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static inline void kvm_set_cpu_l1tf_flush_l1d(void)
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/*
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* This function is called from noinstr interrupt contexts
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* and must be inlined to not get instrumentation.
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*/
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static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void)
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{
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__this_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 1);
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}
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@ -84,7 +88,7 @@ static __always_inline bool kvm_get_cpu_l1tf_flush_l1d(void)
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return __this_cpu_read(irq_stat.kvm_cpu_l1tf_flush_l1d);
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}
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#else /* !IS_ENABLED(CONFIG_KVM_INTEL) */
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static inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
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static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
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#endif /* IS_ENABLED(CONFIG_KVM_INTEL) */
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#endif /* _ASM_X86_HARDIRQ_H */
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@ -212,8 +212,8 @@ __visible noinstr void func(struct pt_regs *regs, \
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irqentry_state_t state = irqentry_enter(regs); \
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u32 vector = (u32)(u8)error_code; \
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\
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instrumentation_begin(); \
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kvm_set_cpu_l1tf_flush_l1d(); \
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instrumentation_begin(); \
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run_irq_on_irqstack_cond(__##func, regs, vector); \
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instrumentation_end(); \
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irqentry_exit(regs, state); \
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@ -250,7 +250,6 @@ static void __##func(struct pt_regs *regs); \
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\
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static __always_inline void instr_##func(struct pt_regs *regs) \
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{ \
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kvm_set_cpu_l1tf_flush_l1d(); \
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run_sysvec_on_irqstack_cond(__##func, regs); \
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} \
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\
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@ -258,6 +257,7 @@ __visible noinstr void func(struct pt_regs *regs) \
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{ \
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irqentry_state_t state = irqentry_enter(regs); \
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\
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kvm_set_cpu_l1tf_flush_l1d(); \
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instrumentation_begin(); \
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instr_##func (regs); \
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instrumentation_end(); \
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@ -288,7 +288,6 @@ static __always_inline void __##func(struct pt_regs *regs); \
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static __always_inline void instr_##func(struct pt_regs *regs) \
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{ \
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__irq_enter_raw(); \
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kvm_set_cpu_l1tf_flush_l1d(); \
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__##func (regs); \
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__irq_exit_raw(); \
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} \
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@ -297,6 +296,7 @@ __visible noinstr void func(struct pt_regs *regs) \
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{ \
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irqentry_state_t state = irqentry_enter(regs); \
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\
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kvm_set_cpu_l1tf_flush_l1d(); \
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instrumentation_begin(); \
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instr_##func (regs); \
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instrumentation_end(); \
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@ -35,6 +35,14 @@ KMSAN_SANITIZE_nmi.o := n
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# If instrumentation of the following files is enabled, boot hangs during
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# first second.
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KCOV_INSTRUMENT_head$(BITS).o := n
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# These are called from save_stack_trace() on debug paths,
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# and produce large amounts of uninteresting coverage.
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KCOV_INSTRUMENT_stacktrace.o := n
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KCOV_INSTRUMENT_dumpstack.o := n
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KCOV_INSTRUMENT_dumpstack_$(BITS).o := n
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KCOV_INSTRUMENT_unwind_orc.o := n
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KCOV_INSTRUMENT_unwind_frame.o := n
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KCOV_INSTRUMENT_unwind_guess.o := n
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CFLAGS_irq.o := -I $(src)/../include/asm/trace
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@ -11,6 +11,7 @@
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#include <linux/fs.h>
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#include <linux/hashtable.h>
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#include <linux/init.h>
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#include <linux/jiffies.h>
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#include <linux/kmsan-checks.h>
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#include <linux/mm.h>
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#include <linux/preempt.h>
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@ -1067,6 +1068,32 @@ u64 kcov_common_handle(void)
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}
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EXPORT_SYMBOL(kcov_common_handle);
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#ifdef CONFIG_KCOV_SELFTEST
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static void __init selftest(void)
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{
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unsigned long start;
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pr_err("running self test\n");
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/*
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* Test that interrupts don't produce spurious coverage.
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* The coverage callback filters out interrupt code, but only
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* after the handler updates preempt count. Some code periodically
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* leaks out of that section and leads to spurious coverage.
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* It's hard to call the actual interrupt handler directly,
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* so we just loop here for a bit waiting for a timer interrupt.
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* We set kcov_mode to enable tracing, but don't setup the area,
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* so any attempt to trace will crash. Note: we must not call any
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* potentially traced functions in this region.
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*/
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start = jiffies;
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current->kcov_mode = KCOV_MODE_TRACE_PC;
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while ((jiffies - start) * MSEC_PER_SEC / HZ < 300)
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;
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current->kcov_mode = 0;
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pr_err("done running self test\n");
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}
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#endif
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static int __init kcov_init(void)
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{
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int cpu;
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@ -1086,6 +1113,10 @@ static int __init kcov_init(void)
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*/
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debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
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#ifdef CONFIG_KCOV_SELFTEST
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selftest();
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#endif
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return 0;
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}
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@ -5,7 +5,7 @@
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# These are called from save_stack_trace() on slub debug path,
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# and produce insane amounts of uninteresting coverage.
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KCOV_INSTRUMENT_module.o := n
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KCOV_INSTRUMENT_main.o := n
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obj-y += main.o
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obj-y += strict_rwx.o
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@ -2173,6 +2173,14 @@ config KCOV_IRQ_AREA_SIZE
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soft interrupts. This specifies the size of those areas in the
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number of unsigned long words.
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config KCOV_SELFTEST
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bool "Perform short selftests on boot"
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depends on KCOV
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help
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Run short KCOV coverage collection selftests on boot.
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On test failure, causes the kernel to panic. Recommended to be
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enabled, ensuring critical functionality works as intended.
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menuconfig RUNTIME_TESTING_MENU
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bool "Runtime Testing"
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default y
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