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pc, pc64: clear debug watchpoint registers on exec and exit

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when a process does an exec syscall, procsetup() is called and
we have to disable the debug watchpoint registers. just clearing
p->dr is not enougth as we are not going thru a procsave() and
procrestore() cycle which would disable and reload the saved
debug registers.

instead of clearing debug registers in procfork(), we should
clear the saved debug registers before a process goes to die
(pexit() calls sched() with up->state = Moribund) as the Proc
structure can get reused for kernel processes (kproc) which
never call procfork() and would therefore have debug registers
loaded.
This commit is contained in:
cinap_lenrek 2019-12-02 23:32:24 +01:00
parent a815273960
commit 5d59a44c21
2 changed files with 28 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

24
sys/src/9/pc/main.c
View file

@ -585,13 +585,18 @@ procsetup(Proc *p)
p->fpstate = FPinit;
fpoff();
cycles(&p->kentry);
p->pcycles = -p->kentry;
memset(p->gdt, 0, sizeof(p->gdt));
p->nldt = 0;
/* clear debug registers */
memset(p->dr, 0, sizeof(p->dr));
if(m->dr7 != 0){
m->dr7 = 0;
putdr7(0);
}
cycles(&p->kentry);
p->pcycles = -p->kentry;
}
void
@ -624,9 +629,6 @@ procfork(Proc *p)
memmove(p->fpsave, up->fpsave, sizeof(FPsave));
p->fpstate = FPinactive;
}
/* clear debug registers */
memset(p->dr, 0, sizeof(p->dr));
splx(s);
}
@ -659,15 +661,17 @@ procsave(Proc *p)
{
uvlong t;
cycles(&t);
p->kentry -= t;
p->pcycles += t;
/* we could just always putdr7(0) but accessing DR7 might be slow in a VM */
if(m->dr7 != 0){
m->dr7 = 0;
putdr7(0);
}
cycles(&t);
p->kentry -= t;
p->pcycles += t;
if(p->state == Moribund)
p->dr[7] = 0;
if(p->fpstate == FPactive){
if(p->state == Moribund)

18
sys/src/9/pc64/main.c
View file

@ -581,6 +581,14 @@ procsetup(Proc *p)
{
p->fpstate = FPinit;
_stts();
/* clear debug registers */
memset(p->dr, 0, sizeof(p->dr));
if(m->dr7 != 0){
m->dr7 = 0;
putdr7(0);
}
cycles(&p->kentry);
p->pcycles = -p->kentry;
}
@ -639,14 +647,16 @@ procsave(Proc *p)
{
uvlong t;
cycles(&t);
p->kentry -= t;
p->pcycles += t;
if(m->dr7 != 0){
m->dr7 = 0;
putdr7(0);
}
cycles(&t);
p->kentry -= t;
p->pcycles += t;
if(p->state == Moribund)
p->dr[7] = 0;
switch(p->fpstate & ~(FPnouser|FPkernel|FPindexm)){
case FPactive | FPpush: