On 12.02.21 13:54, Dmitry Vyukov wrote:
>
> I think we could make KCOV_IN_CTXSW sign bit and then express the check as:
>
> void foo2(unsigned mode) {
> if (((int)(mode & 0x8000000a)) > 0)
> foo();
> }
>
> 0000000000000020 <foo2>:
> 20: 81 e7 0a 00 00 80 and $0x8000000a,%edi
> 26: 7f 08 jg 30 <foo2+0x10>
> 28: c3 retq
>
So ((int)(mode & (KCOV_IN_CTXSW | needed_mode))) > 0?
>
>
>
>> }
>>
>> static notrace unsigned long canonicalize_ip(unsigned long ip)
>> @@ -191,18 +192,26 @@ void notrace __sanitizer_cov_trace_pc(void)
>> struct task_struct *t;
>> unsigned long *area;
>> unsigned long ip = canonicalize_ip(_RET_IP_);
>> - unsigned long pos;
>> + unsigned long pos, idx;
>>
>> t = current;
>> - if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
>> + if (!check_kcov_mode(KCOV_MODE_TRACE_PC | KCOV_MODE_UNIQUE_PC, t))
>> return;
>>
>> area = t->kcov_area;
>> - /* The first 64-bit word is the number of subsequent PCs. */
>> - pos = READ_ONCE(area[0]) + 1;
>> - if (likely(pos < t->kcov_size)) {
>> - area[pos] = ip;
>> - WRITE_ONCE(area[0], pos);
>> + if (likely(t->kcov_mode == KCOV_MODE_TRACE_PC)) {
>
> Does this introduce an additional real of t->kcov_mode?
> If yes, please reuse the value read in check_kcov_mode.
Okay. How do I get that value from check_kcov_mode() to the caller?
Shall I add an additional parameter to check_kcov_mode()?
>
>
>> + /* The first 64-bit word is the number of subsequent PCs. */
>> + pos = READ_ONCE(area[0]) + 1;
>> + if (likely(pos < t->kcov_size)) {
>> + area[pos] = ip;
>> + WRITE_ONCE(area[0], pos);
>> + }
>> + } else {
>> + idx = (ip - canonicalize_ip((unsigned long)&_stext)) / 4;
>> + pos = idx % BITS_PER_LONG;
>> + idx /= BITS_PER_LONG;
>> + if (likely(idx < t->kcov_size))
>> + WRITE_ONCE(area[idx], READ_ONCE(area[idx]) | 1L <<
>> pos);
>> }
>> }
>> EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
>> @@ -474,6 +483,7 @@ static int kcov_mmap(struct file *filep, struct
>> vm_area_struct *vma)
>> goto exit;
>> }
>> if (!kcov->area) {
>> + kcov_debug("mmap(): Allocating 0x%lx bytes\n", size);
>> kcov->area = area;
>> vma->vm_flags |= VM_DONTEXPAND;
>> spin_unlock_irqrestore(&kcov->lock, flags);
>> @@ -515,6 +525,8 @@ static int kcov_get_mode(unsigned long arg)
>> {
>> if (arg == KCOV_TRACE_PC)
>> return KCOV_MODE_TRACE_PC;
>> + else if (arg == KCOV_UNIQUE_PC)
>> + return KCOV_MODE_UNIQUE_PC;
>
> As far as I understand, users can first do KCOV_INIT_UNIQUE and then
> enable KCOV_TRACE_PC, or vice versa.
> It looks somewhat strange. Is it intentional?
I'll fix that.
It's not possible to
> specify buffer size for KCOV_INIT_UNIQUE, so most likely the buffer
> will be either too large or too small for a trace.
No, the buffer will be calculated by KCOV_INIT_UNIQUE based on the size
of the text segment.
- Alex
--
Alexander Lochmann PGP key: 0xBC3EF6FD
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