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bsdkm x86_vecreg: nest counter, and other improvements. #10987

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bsdkm x86_vecreg: nest counter, and other improvements. #10987

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23 changes: 18 additions & 5 deletions bsdkm/x86_vecreg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@ struct wolfkmod_fpu_state_t {

typedef struct wolfkmod_fpu_state_t wolfkmod_fpu_state_t;

#define WOLFKMOD_FPU_MAX_NEST 128

/* The fpu_states array tracks thread id and nesting level of save/restore
* and push/pop vector registers macro calls. It is indexed by raw cpu id,
* and only accessed after the thread calls fpu_kern_enter(), and before
Expand Down Expand Up @@ -142,7 +144,7 @@ int wolfkmod_vecreg_save(int flags_unused)
wolfkmod_print_curthread("wolfkmod_vecreg_save");
#endif

if (fpu_states == NULL) {
if (__predict_false(fpu_states == NULL)) {
printf("error: wolfkmod_vecreg_save: fpu_states null\n");
return (EINVAL);
}
Expand All @@ -160,11 +162,21 @@ int wolfkmod_vecreg_save(int flags_unused)
/* kern fpu is active for this thread. check td_tid and
* increment nesting level. */
lwpid_t td_tid = wolfkmod_fpu_get_tid();
if (td_tid != curthread->td_tid) {
if (__predict_false(td_tid != curthread->td_tid)) {
printf("error: wolfkmod_vecreg_save: got tid = %d, expected %d\n",
td_tid, curthread->td_tid);
return (EINVAL);
}

if (__predict_false(fpu_states[PCPU_GET(cpuid)].nest >=
WOLFKMOD_FPU_MAX_NEST)) {
/* if this nesting depth is reached, something has gone really
* wrong (infinite loop, infinite recursion, etc). */
printf("error: wolfkmod_vecreg_save: excessive fpu nesting (%u)\n",
WOLFKMOD_FPU_MAX_NEST);
Comment on lines +175 to +176

@philljj philljj Jul 23, 2026

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I think it's fine. The point is we're over that high water mark which is very bad.

return (EINVAL);
}

fpu_states[PCPU_GET(cpuid)].nest++;
}
else {
Expand All @@ -177,7 +189,8 @@ int wolfkmod_vecreg_save(int flags_unused)
wolfkmod_fpu_kern_enter();
td_tid = wolfkmod_fpu_get_tid();

if (fpu_states[PCPU_GET(cpuid)].nest != 0 || td_tid != 0) {
if (__predict_false(fpu_states[PCPU_GET(cpuid)].nest != 0 ||
td_tid != 0)) {
printf("error: wolfkmod_fpu_kern_enter() with nest: %d, %d\n",
fpu_states[PCPU_GET(cpuid)].nest, td_tid);
return (EINVAL);
Expand All @@ -197,7 +210,7 @@ void wolfkmod_vecreg_restore(void)
wolfkmod_print_curthread("wolfkmod_vecreg_restore");
#endif

if (fpu_states == NULL) {
if (__predict_false(fpu_states == NULL)) {
printf("error: wolfkmod_vecreg_restore: fpu_states null\n");
return;
}
Expand All @@ -214,7 +227,7 @@ void wolfkmod_vecreg_restore(void)
if (curthread->td_pcb->pcb_flags & PCB_KERNFPU) {
/* kern fpu is active for this thread. check tid and nesting level. */
lwpid_t td_tid = wolfkmod_fpu_get_tid();
if (td_tid != curthread->td_tid) {
if (__predict_false(td_tid != curthread->td_tid)) {
printf("error: wolfkmod_vecreg_restore: got tid = %d, "
"expected %d\n", td_tid, curthread->td_tid);
return;
Expand Down
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