![Anders Roxell](/assets/img/avatar_default.png)
Since __sanitizer_cov_trace_const_cmp4 is marked as notrace, the
function called from __sanitizer_cov_trace_const_cmp4 shouldn't be
traceable either. ftrace_graph_caller() gets called every time func
write_comp_data() gets called if it isn't marked 'notrace'. This is the
backtrace from gdb:
#0 ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
#1 0xffffff8010201920 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151
#2 0xffffff8010439714 in write_comp_data (type=5, arg1=0, arg2=0, ip=18446743524224276596) at ../kernel/kcov.c:116
#3 0xffffff8010439894 in __sanitizer_cov_trace_const_cmp4 (arg1=<optimized out>, arg2=<optimized out>) at ../kernel/kcov.c:188
#4 0xffffff8010201874 in prepare_ftrace_return (self_addr=18446743524226602768, parent=0xffffff801014b918, frame_pointer=18446743524223531344) at ./include/generated/atomic-instrumented.h:27
#5 0xffffff801020194c in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182
Rework so that write_comp_data() that are called from
__sanitizer_cov_trace_*_cmp*() are marked as 'notrace'.
Commit 903e8ff867
("kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace")
missed to mark write_comp_data() as 'notrace'. When that patch was
created gcc-7 was used. In lib/Kconfig.debug
config KCOV_ENABLE_COMPARISONS
depends on $(cc-option,-fsanitize-coverage=trace-cmp)
That code path isn't hit with gcc-7. However, it were that with gcc-8.
Link: http://lkml.kernel.org/r/20181206143011.23719-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
455 lines
11 KiB
C
455 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) "kcov: " fmt
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#define DISABLE_BRANCH_PROFILING
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#include <linux/atomic.h>
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#include <linux/compiler.h>
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#include <linux/errno.h>
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#include <linux/export.h>
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#include <linux/types.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/mm.h>
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#include <linux/preempt.h>
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#include <linux/printk.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/vmalloc.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/kcov.h>
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#include <asm/setup.h>
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/* Number of 64-bit words written per one comparison: */
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#define KCOV_WORDS_PER_CMP 4
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/*
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* kcov descriptor (one per opened debugfs file).
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* State transitions of the descriptor:
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* - initial state after open()
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* - then there must be a single ioctl(KCOV_INIT_TRACE) call
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* - then, mmap() call (several calls are allowed but not useful)
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* - then, ioctl(KCOV_ENABLE, arg), where arg is
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* KCOV_TRACE_PC - to trace only the PCs
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* or
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* KCOV_TRACE_CMP - to trace only the comparison operands
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* - then, ioctl(KCOV_DISABLE) to disable the task.
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* Enabling/disabling ioctls can be repeated (only one task a time allowed).
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*/
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struct kcov {
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/*
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* Reference counter. We keep one for:
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* - opened file descriptor
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* - task with enabled coverage (we can't unwire it from another task)
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*/
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atomic_t refcount;
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/* The lock protects mode, size, area and t. */
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spinlock_t lock;
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enum kcov_mode mode;
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/* Size of arena (in long's for KCOV_MODE_TRACE). */
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unsigned size;
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/* Coverage buffer shared with user space. */
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void *area;
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/* Task for which we collect coverage, or NULL. */
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struct task_struct *t;
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};
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static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
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{
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unsigned int mode;
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/*
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* We are interested in code coverage as a function of a syscall inputs,
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* so we ignore code executed in interrupts.
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*/
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if (!in_task())
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return false;
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mode = READ_ONCE(t->kcov_mode);
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/*
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* There is some code that runs in interrupts but for which
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* in_interrupt() returns false (e.g. preempt_schedule_irq()).
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* READ_ONCE()/barrier() effectively provides load-acquire wrt
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* interrupts, there are paired barrier()/WRITE_ONCE() in
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* kcov_ioctl_locked().
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*/
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barrier();
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return mode == needed_mode;
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}
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static notrace unsigned long canonicalize_ip(unsigned long ip)
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{
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#ifdef CONFIG_RANDOMIZE_BASE
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ip -= kaslr_offset();
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#endif
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return ip;
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}
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/*
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* Entry point from instrumented code.
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* This is called once per basic-block/edge.
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*/
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void notrace __sanitizer_cov_trace_pc(void)
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{
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struct task_struct *t;
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unsigned long *area;
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unsigned long ip = canonicalize_ip(_RET_IP_);
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unsigned long pos;
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t = current;
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if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
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return;
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area = t->kcov_area;
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/* The first 64-bit word is the number of subsequent PCs. */
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pos = READ_ONCE(area[0]) + 1;
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if (likely(pos < t->kcov_size)) {
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area[pos] = ip;
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WRITE_ONCE(area[0], pos);
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}
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
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#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
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static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
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{
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struct task_struct *t;
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u64 *area;
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u64 count, start_index, end_pos, max_pos;
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t = current;
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if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
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return;
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ip = canonicalize_ip(ip);
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/*
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* We write all comparison arguments and types as u64.
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* The buffer was allocated for t->kcov_size unsigned longs.
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*/
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area = (u64 *)t->kcov_area;
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max_pos = t->kcov_size * sizeof(unsigned long);
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count = READ_ONCE(area[0]);
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/* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
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start_index = 1 + count * KCOV_WORDS_PER_CMP;
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end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
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if (likely(end_pos <= max_pos)) {
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area[start_index] = type;
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area[start_index + 1] = arg1;
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area[start_index + 2] = arg2;
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area[start_index + 3] = ip;
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WRITE_ONCE(area[0], count + 1);
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}
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}
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void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
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void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
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void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
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void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
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void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
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_RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
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void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
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_RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
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void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
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_RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
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void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
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{
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write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
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_RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
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void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
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{
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u64 i;
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u64 count = cases[0];
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u64 size = cases[1];
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u64 type = KCOV_CMP_CONST;
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switch (size) {
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case 8:
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type |= KCOV_CMP_SIZE(0);
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break;
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case 16:
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type |= KCOV_CMP_SIZE(1);
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break;
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case 32:
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type |= KCOV_CMP_SIZE(2);
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break;
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case 64:
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type |= KCOV_CMP_SIZE(3);
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break;
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default:
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return;
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}
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for (i = 0; i < count; i++)
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write_comp_data(type, cases[i + 2], val, _RET_IP_);
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}
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EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
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#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
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static void kcov_get(struct kcov *kcov)
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{
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atomic_inc(&kcov->refcount);
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}
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static void kcov_put(struct kcov *kcov)
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{
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if (atomic_dec_and_test(&kcov->refcount)) {
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vfree(kcov->area);
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kfree(kcov);
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}
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}
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void kcov_task_init(struct task_struct *t)
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{
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WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
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barrier();
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t->kcov_size = 0;
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t->kcov_area = NULL;
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t->kcov = NULL;
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}
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void kcov_task_exit(struct task_struct *t)
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{
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struct kcov *kcov;
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kcov = t->kcov;
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if (kcov == NULL)
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return;
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spin_lock(&kcov->lock);
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if (WARN_ON(kcov->t != t)) {
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spin_unlock(&kcov->lock);
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return;
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}
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/* Just to not leave dangling references behind. */
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kcov_task_init(t);
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kcov->t = NULL;
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kcov->mode = KCOV_MODE_INIT;
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spin_unlock(&kcov->lock);
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kcov_put(kcov);
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}
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static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
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{
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int res = 0;
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void *area;
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struct kcov *kcov = vma->vm_file->private_data;
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unsigned long size, off;
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struct page *page;
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area = vmalloc_user(vma->vm_end - vma->vm_start);
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if (!area)
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return -ENOMEM;
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spin_lock(&kcov->lock);
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size = kcov->size * sizeof(unsigned long);
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if (kcov->mode != KCOV_MODE_INIT || vma->vm_pgoff != 0 ||
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vma->vm_end - vma->vm_start != size) {
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res = -EINVAL;
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goto exit;
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}
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if (!kcov->area) {
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kcov->area = area;
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vma->vm_flags |= VM_DONTEXPAND;
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spin_unlock(&kcov->lock);
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for (off = 0; off < size; off += PAGE_SIZE) {
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page = vmalloc_to_page(kcov->area + off);
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if (vm_insert_page(vma, vma->vm_start + off, page))
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WARN_ONCE(1, "vm_insert_page() failed");
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}
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return 0;
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}
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exit:
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spin_unlock(&kcov->lock);
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vfree(area);
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return res;
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}
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static int kcov_open(struct inode *inode, struct file *filep)
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{
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struct kcov *kcov;
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kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
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if (!kcov)
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return -ENOMEM;
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kcov->mode = KCOV_MODE_DISABLED;
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atomic_set(&kcov->refcount, 1);
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spin_lock_init(&kcov->lock);
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filep->private_data = kcov;
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return nonseekable_open(inode, filep);
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}
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static int kcov_close(struct inode *inode, struct file *filep)
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{
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kcov_put(filep->private_data);
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return 0;
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}
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/*
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* Fault in a lazily-faulted vmalloc area before it can be used by
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* __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
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* vmalloc fault handling path is instrumented.
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*/
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static void kcov_fault_in_area(struct kcov *kcov)
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{
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unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
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unsigned long *area = kcov->area;
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unsigned long offset;
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for (offset = 0; offset < kcov->size; offset += stride)
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READ_ONCE(area[offset]);
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}
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static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
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unsigned long arg)
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{
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struct task_struct *t;
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unsigned long size, unused;
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switch (cmd) {
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case KCOV_INIT_TRACE:
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/*
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* Enable kcov in trace mode and setup buffer size.
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* Must happen before anything else.
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*/
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if (kcov->mode != KCOV_MODE_DISABLED)
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return -EBUSY;
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/*
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* Size must be at least 2 to hold current position and one PC.
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* Later we allocate size * sizeof(unsigned long) memory,
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* that must not overflow.
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*/
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size = arg;
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if (size < 2 || size > INT_MAX / sizeof(unsigned long))
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return -EINVAL;
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kcov->size = size;
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kcov->mode = KCOV_MODE_INIT;
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return 0;
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case KCOV_ENABLE:
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/*
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* Enable coverage for the current task.
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* At this point user must have been enabled trace mode,
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* and mmapped the file. Coverage collection is disabled only
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* at task exit or voluntary by KCOV_DISABLE. After that it can
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* be enabled for another task.
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*/
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if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
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return -EINVAL;
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t = current;
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if (kcov->t != NULL || t->kcov != NULL)
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return -EBUSY;
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if (arg == KCOV_TRACE_PC)
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kcov->mode = KCOV_MODE_TRACE_PC;
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else if (arg == KCOV_TRACE_CMP)
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#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
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kcov->mode = KCOV_MODE_TRACE_CMP;
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#else
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return -ENOTSUPP;
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#endif
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else
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return -EINVAL;
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kcov_fault_in_area(kcov);
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/* Cache in task struct for performance. */
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t->kcov_size = kcov->size;
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t->kcov_area = kcov->area;
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/* See comment in check_kcov_mode(). */
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barrier();
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WRITE_ONCE(t->kcov_mode, kcov->mode);
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t->kcov = kcov;
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kcov->t = t;
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/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
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kcov_get(kcov);
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return 0;
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case KCOV_DISABLE:
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/* Disable coverage for the current task. */
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unused = arg;
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if (unused != 0 || current->kcov != kcov)
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return -EINVAL;
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t = current;
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if (WARN_ON(kcov->t != t))
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return -EINVAL;
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kcov_task_init(t);
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kcov->t = NULL;
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kcov->mode = KCOV_MODE_INIT;
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kcov_put(kcov);
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return 0;
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default:
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return -ENOTTY;
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}
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}
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static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
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{
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struct kcov *kcov;
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int res;
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kcov = filep->private_data;
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spin_lock(&kcov->lock);
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res = kcov_ioctl_locked(kcov, cmd, arg);
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spin_unlock(&kcov->lock);
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return res;
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}
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static const struct file_operations kcov_fops = {
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.open = kcov_open,
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.unlocked_ioctl = kcov_ioctl,
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.compat_ioctl = kcov_ioctl,
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.mmap = kcov_mmap,
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.release = kcov_close,
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};
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static int __init kcov_init(void)
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{
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/*
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* The kcov debugfs file won't ever get removed and thus,
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* there is no need to protect it against removal races. The
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* use of debugfs_create_file_unsafe() is actually safe here.
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*/
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if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) {
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pr_err("failed to create kcov in debugfs\n");
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return -ENOMEM;
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}
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return 0;
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}
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device_initcall(kcov_init);
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