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Wed, 18 Mar 2026 09:27:09 -0700 (PDT) From: Jann Horn Date: Wed, 18 Mar 2026 17:26:58 +0100 Subject: [PATCH v2 1/4] sched: Ensure matching stack state for kcov disable/enable on switch Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260318-kcov-extrecord-v2-1-2522da6fcd3f@google.com> References: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> In-Reply-To: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> To: Dmitry Vyukov , Andrey Konovalov , Alexander Potapenko Cc: Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, llvm@lists.linux.dev, Jann Horn , Ingo Molnar , Peter Zijlstra X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1773851224; l=1827; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=YPl8dC+FWNYbig6FC8CWhTRlpJIuO11/DPHxoh5KsiM=; b=hiUxadU509ZAxL1hocvzwSwvDRdcyHk3+StHxZdd86Fp+GpZ8sfNB5SkrMjXjtjneFMJtxF9p H2PQmiAQWOaA5WPKypgYfFOvA7+Dj5DZOPpGlWaNRzQqx0U00Q8wSHu X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= Ensure that kcov is disabled and enabled with the same call stack. This will be relied on by subsequent patches for recording function entry/exit records via kcov. This patch should not affect compilation of normal kernels without KCOV (though it changes "inline" to "__always_inline"). To: Ingo Molnar To: Peter Zijlstra Signed-off-by: Jann Horn --- kernel/sched/core.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b7f77c165a6e..c470f0a669ec 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5072,8 +5072,10 @@ static inline void kmap_local_sched_in(void) * * prepare_task_switch sets up locking and calls architecture specific * hooks. + * + * Must be inlined for kcov_prepare_switch(). */ -static inline void +static __always_inline void prepare_task_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) __must_hold(__rq_lockp(rq)) @@ -5149,7 +5151,6 @@ static struct rq *finish_task_switch(struct task_stru= ct *prev) tick_nohz_task_switch(); finish_lock_switch(rq); finish_arch_post_lock_switch(); - kcov_finish_switch(current); /* * kmap_local_sched_out() is invoked with rq::lock held and * interrupts disabled. There is no requirement for that, but the @@ -5295,7 +5296,13 @@ context_switch(struct rq *rq, struct task_struct *pr= ev, switch_to(prev, next, prev); barrier(); =20 - return finish_task_switch(prev); + rq =3D finish_task_switch(prev); + /* + * This has to happen outside finish_task_switch() to ensure that + * entry/exit records are balanced. + */ + kcov_finish_switch(current); + return rq; } =20 /* --=20 2.53.0.851.ga537e3e6e9-goog From nobody Mon Apr 6 16:41:39 2026 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2D43F3FFABE for ; Wed, 18 Mar 2026 16:27:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.49 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773851240; cv=none; b=qTmGkwx8DRnbvKE09U4q03HKJlKI3ixhIoeyKQUyuzeRt5iuIEXqQVnwsAUkEvAAn46LlV3Ynzwrq3YQyv91TIcMkxfFK+IdoNbIwgQ9unYnfHacQYkTmYxLFHvQBSD05u7cKelkrss+xbE9L0gSbwIAE9+LShtZjGqId8FF1GM= ARC-Message-Signature: i=1; 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Wed, 18 Mar 2026 09:27:10 -0700 (PDT) Received: from localhost ([2a00:79e0:288a:8:c66d:1e51:595a:925]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-43b5184961csm9805144f8f.6.2026.03.18.09.27.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 09:27:10 -0700 (PDT) From: Jann Horn Date: Wed, 18 Mar 2026 17:26:59 +0100 Subject: [PATCH v2 2/4] kcov: wire up compiler instrumentation for CONFIG_KCOV_EXT_RECORDS Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260318-kcov-extrecord-v2-2-2522da6fcd3f@google.com> References: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> In-Reply-To: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> To: Dmitry Vyukov , Andrey Konovalov , Alexander Potapenko Cc: Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, llvm@lists.linux.dev, Jann Horn , Josh Poimboeuf , Peter Zijlstra X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1773851224; l=5575; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=/5iKMb3ycj7sI45IkWou/fRJrMIENtP9YU3ZYrOJJ2E=; b=Pvlz50le1Rl6k4pchGWj+xOX1hDMosBffmKuAV4aHVkb4OKCez0m7tlYUJsGdHDNeLmsLo+rH gLx2i4q5CnICKzlmfIv0hpQoOCa0p9MHRul4gkWlLugTxFO0sx8iu52 X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= This is the first half of CONFIG_KCOV_EXT_RECORDS. Set the appropriate compiler flags to call separate hooks for function entry/exit, and provide these hooks, but don't make it visible in the KCOV UAPI yet. With -fsanitize-coverage=3Dtrace-pc-entry-exit, the compiler behavior chang= es as follows: - The __sanitizer_cov_trace_pc() call on function entry is replaced with a call to __sanitizer_cov_trace_pc_entry(); so for now, __sanitizer_cov_trace_pc_entry() must be treated the same way as __sanitizer_cov_trace_pc(). - On function exit, an extra call to __sanitizer_cov_trace_pc_exit() happens; since function exit produced no coverage in the old UAPI, __sanitizer_cov_trace_pc_exit() should do nothing for now. This feature was added to LLVM in commit: https://github.com/llvm/llvm-project/commit/dc5c6d008f487eea8f5d646011f9b3d= ca6caebd7 Cc: Josh Poimboeuf Cc: Peter Zijlstra Reviewed-by: Dmitry Vyukov Signed-off-by: Jann Horn --- include/linux/kcov.h | 2 ++ kernel/kcov.c | 34 +++++++++++++++++++++++++++------- lib/Kconfig.debug | 12 ++++++++++++ scripts/Makefile.kcov | 2 ++ tools/objtool/check.c | 2 ++ 5 files changed, 45 insertions(+), 7 deletions(-) diff --git a/include/linux/kcov.h b/include/linux/kcov.h index 0143358874b0..e5502d674029 100644 --- a/include/linux/kcov.h +++ b/include/linux/kcov.h @@ -81,6 +81,8 @@ typedef unsigned long long kcov_u64; #endif =20 void __sanitizer_cov_trace_pc(void); +void __sanitizer_cov_trace_pc_entry(void); +void __sanitizer_cov_trace_pc_exit(void); void __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2); void __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2); void __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2); diff --git a/kernel/kcov.c b/kernel/kcov.c index 0b369e88c7c9..86b681c7865c 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -202,15 +202,10 @@ static notrace unsigned long canonicalize_ip(unsigned= long ip) return ip; } =20 -/* - * Entry point from instrumented code. - * This is called once per basic-block/edge. - */ -void notrace __sanitizer_cov_trace_pc(void) +static __always_inline void notrace kcov_add_pc_record(unsigned long recor= d) { struct task_struct *t; unsigned long *area; - unsigned long ip =3D canonicalize_ip(_RET_IP_); unsigned long pos; =20 t =3D current; @@ -230,11 +225,36 @@ void notrace __sanitizer_cov_trace_pc(void) */ WRITE_ONCE(area[0], pos); barrier(); - area[pos] =3D ip; + area[pos] =3D record; } } + +/* + * Entry point from instrumented code. + * This is called once per basic-block/edge. + */ +void notrace __sanitizer_cov_trace_pc(void) +{ + kcov_add_pc_record(canonicalize_ip(_RET_IP_)); +} EXPORT_SYMBOL(__sanitizer_cov_trace_pc); =20 +#ifdef CONFIG_KCOV_EXT_RECORDS +void notrace __sanitizer_cov_trace_pc_entry(void) +{ + unsigned long record =3D canonicalize_ip(_RET_IP_); + + /* + * This hook replaces __sanitizer_cov_trace_pc() for the function entry + * basic block; it should still emit a record even in classic kcov mode. + */ + kcov_add_pc_record(record); +} +void notrace __sanitizer_cov_trace_pc_exit(void) +{ +} +#endif + #ifdef CONFIG_KCOV_ENABLE_COMPARISONS static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip) { diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 93f356d2b3d9..58686a99c40a 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2215,6 +2215,18 @@ config KCOV =20 For more details, see Documentation/dev-tools/kcov.rst. =20 +config KCOV_EXT_RECORDS + bool "Support extended KCOV records with function entry/exit records" + depends on KCOV + depends on 64BIT + depends on $(cc-option,-fsanitize-coverage=3Dtrace-pc-entry-exit) + help + Extended KCOV records allow distinguishing between multiple types of + records: Normal edge coverage, function entry, and function exit. + + This will likely cause a small additional slowdown compared to normal + KCOV. + config KCOV_ENABLE_COMPARISONS bool "Enable comparison operands collection by KCOV" depends on KCOV diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov index 78305a84ba9d..aa0be904268f 100644 --- a/scripts/Makefile.kcov +++ b/scripts/Makefile.kcov @@ -1,10 +1,12 @@ # SPDX-License-Identifier: GPL-2.0-only kcov-flags-y +=3D -fsanitize-coverage=3Dtrace-pc +kcov-flags-$(CONFIG_KCOV_EXT_RECORDS) +=3D -fsanitize-coverage=3Dtrace-pc= -entry-exit kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS) +=3D -fsanitize-coverage=3Dtr= ace-cmp =20 kcov-rflags-y +=3D -Cpasses=3Dsancov-module kcov-rflags-y +=3D -Cllvm-args=3D-sanitizer-coverage-level=3D3 kcov-rflags-y +=3D -Cllvm-args=3D-sanitizer-coverage-trace-pc +kcov-rflags-$(CONFIG_KCOV_EXT_RECORDS) +=3D -Cllvm-args=3D-sanitizer-cove= rage-trace-pc-entry-exit kcov-rflags-$(CONFIG_KCOV_ENABLE_COMPARISONS) +=3D -Cllvm-args=3D-sanitize= r-coverage-trace-compares =20 export CFLAGS_KCOV :=3D $(kcov-flags-y) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index a30379e4ff97..ae3127227621 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1251,6 +1251,8 @@ static const char *uaccess_safe_builtin[] =3D { "write_comp_data", "check_kcov_mode", "__sanitizer_cov_trace_pc", + "__sanitizer_cov_trace_pc_entry", + "__sanitizer_cov_trace_pc_exit", "__sanitizer_cov_trace_const_cmp1", "__sanitizer_cov_trace_const_cmp2", "__sanitizer_cov_trace_const_cmp4", --=20 2.53.0.851.ga537e3e6e9-goog From nobody Mon Apr 6 16:41:39 2026 Received: from mail-wm1-f44.google.com (mail-wm1-f44.google.com [209.85.128.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 688DA3F2117 for ; 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Wed, 18 Mar 2026 09:27:11 -0700 (PDT) Received: from localhost ([2a00:79e0:288a:8:c66d:1e51:595a:925]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-43b51899617sm9479049f8f.31.2026.03.18.09.27.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 09:27:11 -0700 (PDT) From: Jann Horn Date: Wed, 18 Mar 2026 17:27:00 +0100 Subject: [PATCH v2 3/4] kcov: refactor mode check out of check_kcov_mode() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260318-kcov-extrecord-v2-3-2522da6fcd3f@google.com> References: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> In-Reply-To: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> To: Dmitry Vyukov , Andrey Konovalov , Alexander Potapenko Cc: Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, llvm@lists.linux.dev, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1773851224; l=4314; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=GMMooYTgIpzRxthzUDxwLp4xKLUvtXfQIrOtNj3xG6o=; b=ubeizWU7XosiwCUKAEAZUXL1Q5MjoVYWTgMWVezx+AP3JNdQUC7UZ2ZhqtSoXWoWtZVUY+Iq1 IX5YDd6rFdVAEaAA4kXAvWENoyBRDOrwWqpuLocf+KNg0Hfew97r04r X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= The following patch will need to check t->kcov_mode in different ways at different check_kcov_mode() call sites. In preparation for that, move the mode check up the call hierarchy. Signed-off-by: Jann Horn --- kernel/kcov.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/kernel/kcov.c b/kernel/kcov.c index 86b681c7865c..7edb39e18bfe 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -171,10 +171,8 @@ static __always_inline bool in_softirq_really(void) return in_serving_softirq() && !in_hardirq() && !in_nmi(); } =20 -static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct tas= k_struct *t) +static notrace bool check_kcov_context(struct task_struct *t) { - unsigned int mode; - /* * We are interested in code coverage as a function of a syscall inputs, * so we ignore code executed in interrupts, unless we are in a remote @@ -182,7 +180,6 @@ static notrace bool check_kcov_mode(enum kcov_mode need= ed_mode, struct task_stru */ if (!in_task() && !(in_softirq_really() && t->kcov_softirq)) return false; - mode =3D READ_ONCE(t->kcov_mode); /* * There is some code that runs in interrupts but for which * in_interrupt() returns false (e.g. preempt_schedule_irq()). @@ -191,7 +188,7 @@ static notrace bool check_kcov_mode(enum kcov_mode need= ed_mode, struct task_stru * kcov_start(). */ barrier(); - return mode =3D=3D needed_mode; + return true; } =20 static notrace unsigned long canonicalize_ip(unsigned long ip) @@ -202,14 +199,12 @@ static notrace unsigned long canonicalize_ip(unsigned= long ip) return ip; } =20 -static __always_inline void notrace kcov_add_pc_record(unsigned long recor= d) +static __always_inline void notrace kcov_add_pc_record(struct task_struct = *t, unsigned long record) { - struct task_struct *t; unsigned long *area; unsigned long pos; =20 - t =3D current; - if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t)) + if (!check_kcov_context(t)) return; =20 area =3D t->kcov_area; @@ -217,7 +212,7 @@ static __always_inline void notrace kcov_add_pc_record(= unsigned long record) pos =3D READ_ONCE(area[0]) + 1; if (likely(pos < t->kcov_size)) { /* Previously we write pc before updating pos. However, some - * early interrupt code could bypass check_kcov_mode() check + * early interrupt code could bypass check_kcov_context() check * and invoke __sanitizer_cov_trace_pc(). If such interrupt is * raised between writing pc and updating pos, the pc could be * overitten by the recursive __sanitizer_cov_trace_pc(). @@ -235,20 +230,28 @@ static __always_inline void notrace kcov_add_pc_recor= d(unsigned long record) */ void notrace __sanitizer_cov_trace_pc(void) { - kcov_add_pc_record(canonicalize_ip(_RET_IP_)); + struct task_struct *cur =3D current; + + if (READ_ONCE(cur->kcov_mode) !=3D KCOV_MODE_TRACE_PC) + return; + kcov_add_pc_record(cur, canonicalize_ip(_RET_IP_)); } EXPORT_SYMBOL(__sanitizer_cov_trace_pc); =20 #ifdef CONFIG_KCOV_EXT_RECORDS void notrace __sanitizer_cov_trace_pc_entry(void) { + struct task_struct *cur =3D current; unsigned long record =3D canonicalize_ip(_RET_IP_); + unsigned int kcov_mode =3D READ_ONCE(cur->kcov_mode); =20 /* * This hook replaces __sanitizer_cov_trace_pc() for the function entry * basic block; it should still emit a record even in classic kcov mode. */ - kcov_add_pc_record(record); + if (kcov_mode !=3D KCOV_MODE_TRACE_PC) + return; 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Wed, 18 Mar 2026 09:27:14 -0700 (PDT) Received: from localhost ([2a00:79e0:288a:8:c66d:1e51:595a:925]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-486f4b9bb2esm20905255e9.20.2026.03.18.09.27.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 09:27:13 -0700 (PDT) From: Jann Horn Date: Wed, 18 Mar 2026 17:27:01 +0100 Subject: [PATCH v2 4/4] kcov: introduce extended PC coverage collection mode Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260318-kcov-extrecord-v2-4-2522da6fcd3f@google.com> References: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> In-Reply-To: <20260318-kcov-extrecord-v2-0-2522da6fcd3f@google.com> To: Dmitry Vyukov , Andrey Konovalov , Alexander Potapenko Cc: Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, llvm@lists.linux.dev, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1773851224; l=5681; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=52RZwge2HiHzFPyKFZk5GPDAZYf3/NA1Sia8icDS9Tc=; b=tLZgiv8MkBfdhi/W3flmRalK3OU9W4IRmqGFBLRSj8kDcwSh7Nei0AFtOSJwz3H/1nqGUg3dn dDZNtgFXJmxB6aSRsbo3EwV8RxFRYsCND/pdn97snaexZB7ADSu8WBA X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= This is the second half of CONFIG_KCOV_EXT_RECORDS. Introduce a new KCOV mode KCOV_TRACE_PC_EXT which replaces the upper 8 bits of recorded instruction pointers with metadata. For now, userspace can use this metadata to distinguish three types of records: - function entry - function exit - normal basic block inside the function Internally, this new mode is represented as a variant of KCOV_MODE_TRACE_PC, distinguished with the flag KCOV_EXT_FORMAT. Store this flag as part of the mode in task_struct::kcov_mode and in kcov::mode to avoid having to pass it around separately everywhere. Signed-off-by: Jann Horn --- include/linux/kcov.h | 7 +++++++ include/uapi/linux/kcov.h | 12 ++++++++++++ kernel/kcov.c | 39 ++++++++++++++++++++++++++++++++++----- 3 files changed, 53 insertions(+), 5 deletions(-) diff --git a/include/linux/kcov.h b/include/linux/kcov.h index e5502d674029..455302b1cd1c 100644 --- a/include/linux/kcov.h +++ b/include/linux/kcov.h @@ -25,8 +25,15 @@ enum kcov_mode { KCOV_MODE_REMOTE =3D 4, }; =20 +/* + * Modifier for KCOV_MODE_TRACE_PC to record function entry/exit marked wi= th + * metadata bits. + */ +#define KCOV_EXT_FORMAT (1 << 29) #define KCOV_IN_CTXSW (1 << 30) =20 +#define KCOV_MODE_TRACE_PC_EXT (KCOV_MODE_TRACE_PC | KCOV_EXT_FORMAT) + void kcov_task_init(struct task_struct *t); void kcov_task_exit(struct task_struct *t); =20 diff --git a/include/uapi/linux/kcov.h b/include/uapi/linux/kcov.h index ed95dba9fa37..8d8a233bd61f 100644 --- a/include/uapi/linux/kcov.h +++ b/include/uapi/linux/kcov.h @@ -35,8 +35,20 @@ enum { KCOV_TRACE_PC =3D 0, /* Collecting comparison operands mode. */ KCOV_TRACE_CMP =3D 1, + /* + * Extended PC coverage collection mode. + * In this mode, the top byte of the PC is replaced with flag bits + * (KCOV_RECORDFLAG_*). + */ + KCOV_TRACE_PC_EXT =3D 2, }; =20 +#define KCOV_RECORD_IP_MASK 0x00ffffffffffffff +#define KCOV_RECORDFLAG_TYPEMASK 0xf000000000000000 +#define KCOV_RECORDFLAG_TYPE_NORMAL 0xf000000000000000 +#define KCOV_RECORDFLAG_TYPE_ENTRY 0x0000000000000000 +#define KCOV_RECORDFLAG_TYPE_EXIT 0x1000000000000000 + /* * The format for the types of collected comparisons. * diff --git a/kernel/kcov.c b/kernel/kcov.c index 7edb39e18bfe..3cd4ee4cc310 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -55,7 +55,12 @@ struct kcov { refcount_t refcount; /* The lock protects mode, size, area and t. */ spinlock_t lock; - enum kcov_mode mode __guarded_by(&lock); + /* + * Mode, consists of: + * - enum kcov_mode + * - flag KCOV_EXT_FORMAT + */ + unsigned int mode __guarded_by(&lock); /* Size of arena (in long's). */ unsigned int size __guarded_by(&lock); /* Coverage buffer shared with user space. */ @@ -232,8 +237,14 @@ void notrace __sanitizer_cov_trace_pc(void) { struct task_struct *cur =3D current; =20 - if (READ_ONCE(cur->kcov_mode) !=3D KCOV_MODE_TRACE_PC) + if ((READ_ONCE(cur->kcov_mode) & ~KCOV_EXT_FORMAT) !=3D KCOV_MODE_TRACE_P= C) return; + /* + * No bitops are needed here for setting the record type because + * KCOV_RECORDFLAG_TYPE_NORMAL has the high bits set. + * This relies on userspace not caring about the rest of the top byte + * for KCOV_RECORDFLAG_TYPE_NORMAL records. + */ kcov_add_pc_record(cur, canonicalize_ip(_RET_IP_)); } EXPORT_SYMBOL(__sanitizer_cov_trace_pc); @@ -249,12 +260,28 @@ void notrace __sanitizer_cov_trace_pc_entry(void) * This hook replaces __sanitizer_cov_trace_pc() for the function entry * basic block; it should still emit a record even in classic kcov mode. */ - if (kcov_mode !=3D KCOV_MODE_TRACE_PC) + if ((kcov_mode & ~KCOV_EXT_FORMAT) !=3D KCOV_MODE_TRACE_PC) return; + if ((kcov_mode & KCOV_EXT_FORMAT) !=3D 0) + record =3D (record & KCOV_RECORD_IP_MASK) | KCOV_RECORDFLAG_TYPE_ENTRY; kcov_add_pc_record(cur, record); } void notrace __sanitizer_cov_trace_pc_exit(void) { + struct task_struct *cur =3D current; + unsigned long record; + + /* + * This hook is not called at the beginning of a basic block; the basic + * block from which the hook was invoked is already covered by a + * preceding hook call. + * So unlike __sanitizer_cov_trace_pc_entry(), this PC should only be + * reported in extended mode, where function exit events are recorded. + */ + if (READ_ONCE(cur->kcov_mode) !=3D KCOV_MODE_TRACE_PC_EXT) + return; + record =3D (canonicalize_ip(_RET_IP_) & KCOV_RECORD_IP_MASK) | KCOV_RECOR= DFLAG_TYPE_EXIT; + kcov_add_pc_record(cur, record); } #endif =20 @@ -377,7 +404,7 @@ EXPORT_SYMBOL(__sanitizer_cov_trace_switch); #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */ =20 static void kcov_start(struct task_struct *t, struct kcov *kcov, - unsigned int size, void *area, enum kcov_mode mode, + unsigned int size, void *area, unsigned int mode, int sequence) { kcov_debug("t =3D %px, size =3D %u, area =3D %px\n", t, size, area); @@ -577,6 +604,8 @@ static int kcov_get_mode(unsigned long arg) #else return -ENOTSUPP; #endif + else if (arg =3D=3D KCOV_TRACE_PC_EXT) + return IS_ENABLED(CONFIG_KCOV_EXT_RECORDS) ? KCOV_MODE_TRACE_PC_EXT : -E= NOTSUPP; else return -EINVAL; } @@ -1089,7 +1118,7 @@ void kcov_remote_stop(void) * and kcov_remote_stop(), hence the sequence check. */ if (sequence =3D=3D kcov->sequence && kcov->remote) - kcov_move_area(kcov->mode, kcov->area, kcov->size, area); + kcov_move_area(kcov->mode & ~KCOV_EXT_FORMAT, kcov->area, kcov->size, ar= ea); spin_unlock(&kcov->lock); =20 if (in_task()) { --=20 2.53.0.851.ga537e3e6e9-goog