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libkvm: Fix kvm_getloadavg() on modern kernel vmcores

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Fix kvm_getloadavg() to work correctly on vmcores for modern kernel
versions.  The kernels no longer include the `_fscale` symbol causing
the kvm_nlist() invocation to fail.  The code seemed to already assume
that `_fscale` could be missing but the early kvm_nlist() result check
has caused the function to fail if any symbol were missing.  Modify
it to only treat `_averunnable` as obligatory, and handle missing
`_fscale` gracefully.

Sponsored by:   The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D32884
This commit is contained in:
Michał Górny 2021-11-07 22:11:52 +01:00 committed by John Baldwin
parent e9aeb50797
commit 8099a35446
1 changed files with 4 additions and 5 deletions
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9
lib/libkvm/kvm_getloadavg.c
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@ -62,7 +62,6 @@ int
kvm_getloadavg(kvm_t *kd, double loadavg[], int nelem) kvm_getloadavg(kvm_t *kd, double loadavg[], int nelem)
{ {
struct loadavg loadinfo; struct loadavg loadinfo;
struct nlist *p;
int fscale, i; int fscale, i;
if (ISALIVE(kd)) if (ISALIVE(kd))
@ -74,10 +73,9 @@ kvm_getloadavg(kvm_t *kd, double loadavg[], int nelem)
return (-1); return (-1);
} }
if (kvm_nlist(kd, nl) != 0) { if (kvm_nlist(kd, nl) != 0 && nl[X_AVERUNNABLE].n_type == 0) {
for (p = nl; p->n_type != 0; ++p);
_kvm_err(kd, kd->program, _kvm_err(kd, kd->program,
"%s: no such symbol", p->n_name); "%s: no such symbol", nl[X_AVERUNNABLE].n_name);
return (-1); return (-1);
} }
@ -92,7 +90,8 @@ kvm_getloadavg(kvm_t *kd, double loadavg[], int nelem)
* Old kernels have fscale separately; if not found assume * Old kernels have fscale separately; if not found assume
* running new format. * running new format.
*/ */
if (!KREAD(kd, nl[X_FSCALE].n_value, &fscale)) if (nl[X_FSCALE].n_type != 0 &&
!KREAD(kd, nl[X_FSCALE].n_value, &fscale))
loadinfo.fscale = fscale; loadinfo.fscale = fscale;
nelem = MIN(nelem, (int)(sizeof(loadinfo.ldavg) / sizeof(fixpt_t))); nelem = MIN(nelem, (int)(sizeof(loadinfo.ldavg) / sizeof(fixpt_t)));