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9528d32873
kcov_remote_start_usb_softirq() the begin of urb's completion callback.
HCDs marked HCD_BH will invoke this function from the softirq and
in_serving_softirq() will detect this properly.
Root-HUB (RH) requests will not be delayed to softirq but complete
immediately in IRQ context.
This will confuse kcov because in_serving_softirq() will report true if
the softirq is served after the hardirq and if the softirq got
interrupted by the hardirq in which currently runs.
This was addressed by simply disabling interrupts in
kcov_remote_start_usb_softirq() which avoided the interruption by the RH
while a regular completion callback was invoked.
This not only changes the behaviour while kconv is enabled but also
breaks PREEMPT_RT because now sleeping locks can no longer be acquired.
Revert the previous fix. Address the issue by invoking
kcov_remote_start_usb() only if the context is just "serving softirqs"
which is identified by checking in_serving_softirq() and in_hardirq()
must be false.
Fixes: f85d39dd7e ("kcov, usb: disable interrupts in kcov_remote_start_usb_softirq")
Cc: stable <stable@kernel.org>
Reported-by: Yunseong Kim <ysk@kzalloc.com>
Closes: https://lore.kernel.org/all/20250725201400.1078395-2-ysk@kzalloc.com/
Tested-by: Yunseong Kim <ysk@kzalloc.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250811082745.ycJqBXMs@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
113 lines
3.2 KiB
C
113 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_KCOV_H
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#define _LINUX_KCOV_H
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#include <linux/sched.h>
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#include <uapi/linux/kcov.h>
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struct task_struct;
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#ifdef CONFIG_KCOV
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enum kcov_mode {
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/* Coverage collection is not enabled yet. */
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KCOV_MODE_DISABLED = 0,
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/* KCOV was initialized, but tracing mode hasn't been chosen yet. */
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KCOV_MODE_INIT = 1,
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/*
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* Tracing coverage collection mode.
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* Covered PCs are collected in a per-task buffer.
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*/
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KCOV_MODE_TRACE_PC = 2,
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/* Collecting comparison operands mode. */
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KCOV_MODE_TRACE_CMP = 3,
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/* The process owns a KCOV remote reference. */
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KCOV_MODE_REMOTE = 4,
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};
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#define KCOV_IN_CTXSW (1 << 30)
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void kcov_task_init(struct task_struct *t);
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void kcov_task_exit(struct task_struct *t);
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#define kcov_prepare_switch(t) \
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do { \
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(t)->kcov_mode |= KCOV_IN_CTXSW; \
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} while (0)
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#define kcov_finish_switch(t) \
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do { \
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(t)->kcov_mode &= ~KCOV_IN_CTXSW; \
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} while (0)
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/* See Documentation/dev-tools/kcov.rst for usage details. */
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void kcov_remote_start(u64 handle);
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void kcov_remote_stop(void);
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u64 kcov_common_handle(void);
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static inline void kcov_remote_start_common(u64 id)
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{
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kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, id));
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}
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static inline void kcov_remote_start_usb(u64 id)
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{
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kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_USB, id));
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}
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/*
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* The softirq flavor of kcov_remote_*() functions is introduced as a temporary
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* work around for kcov's lack of nested remote coverage sections support in
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* task context. Adding support for nested sections is tracked in:
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* https://bugzilla.kernel.org/show_bug.cgi?id=210337
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*/
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static inline void kcov_remote_start_usb_softirq(u64 id)
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{
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if (in_serving_softirq() && !in_hardirq())
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kcov_remote_start_usb(id);
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}
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static inline void kcov_remote_stop_softirq(void)
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{
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if (in_serving_softirq() && !in_hardirq())
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kcov_remote_stop();
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}
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#ifdef CONFIG_64BIT
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typedef unsigned long kcov_u64;
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#else
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typedef unsigned long long kcov_u64;
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#endif
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void __sanitizer_cov_trace_pc(void);
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void __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2);
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void __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2);
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void __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2);
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void __sanitizer_cov_trace_cmp8(kcov_u64 arg1, kcov_u64 arg2);
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void __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2);
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void __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2);
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void __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2);
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void __sanitizer_cov_trace_const_cmp8(kcov_u64 arg1, kcov_u64 arg2);
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void __sanitizer_cov_trace_switch(kcov_u64 val, void *cases);
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#else
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static inline void kcov_task_init(struct task_struct *t) {}
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static inline void kcov_task_exit(struct task_struct *t) {}
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static inline void kcov_prepare_switch(struct task_struct *t) {}
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static inline void kcov_finish_switch(struct task_struct *t) {}
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static inline void kcov_remote_start(u64 handle) {}
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static inline void kcov_remote_stop(void) {}
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static inline u64 kcov_common_handle(void)
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{
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return 0;
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}
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static inline void kcov_remote_start_common(u64 id) {}
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static inline void kcov_remote_start_usb(u64 id) {}
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static inline void kcov_remote_start_usb_softirq(u64 id) {}
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static inline void kcov_remote_stop_softirq(void) {}
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#endif /* CONFIG_KCOV */
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#endif /* _LINUX_KCOV_H */
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