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From: Peter Wemm <peter@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Cc: 
Subject: PERFORCE change 140994 for review
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http://perforce.freebsd.org/chv.cgi?CH=140994

Change 140994 by peter@peter_daintree on 2008/05/01 17:37:28

	Update.  Use the correct fields.  Look for pcpu_size in the kernel
	to adapt to any layout changes.  (Let the consumer deal with variance
	rather than guaranteeing that libkvm breaks first)

Affected files ...

.. //depot/projects/hammer/lib/libkvm/kvm_amd64.c#24 edit

Differences ...

==== //depot/projects/hammer/lib/libkvm/kvm_amd64.c#24 (text+ko) ====

@@ -76,7 +76,8 @@
 	size_t		mmapsize;
 	pml4_entry_t	*PML4;
 	int		mp_maxcpus;
-	struct pcpu	*pcpu;
+	int		pcpu_recsize;
+	char		*pcpu;
 };
 
 /*
@@ -375,9 +376,23 @@
 		/* UP system; symbol doesn't exist */
 		vmst->mp_maxcpus = 1;
 	}
-	vm->pcpu = _kvm_malloc(kd, sizeof(struct pcpu) * vm->mp_maxcpus);
+	/*
+	 * The __pcpu array may have different inter-record padding or may
+	 * grow additional fields.  We have to adapt the best we can.
+	 */
+	nlist[0].n_name = "pcpu_size";
+	nlist[1].n_name = 0;
+	if (kvm_nlist(kd, nlist) == 0) {
+		if (kvm_read(kd, nlist[0].n_value, &vm->pcpu_recsize,
+		    sizeof(vm->pcpu_recsize)) != sizeof(vm->pcpu_recsize)) {
+			_kvm_err(kd, kd->program, "cannot read pcpu_size");
+	} else {
+		/* Older kernel's dont have it. Hope for the best. */
+		vmst->pcpu_recsize = sizeof(struct pcpu);
+	}
+	vm->pcpu = _kvm_malloc(kd, vm->pcpu_recsize * vm->mp_maxcpus);
 
-	nlist[0].n_name = "pcpu";
+	nlist[0].n_name = "__pcpu";
 	nlist[1].n_name = 0;
 
 	if (kvm_nlist(kd, nlist) != 0) {
@@ -385,8 +400,8 @@
 		return (-1);
 	}
 	if (kvm_read(kd, nlist[0].n_value, vm->pcpu,
-	    sizeof(struct pcpu) * vm->mp_maxcpus) !=
-	    sizeof(struct pcpu) * vm->mp_maxcpus) {
+	    vm->pcpu_recsize * vm->mp_maxcpus) !=
+	    vm->pcpu_recsize * vm->mp_maxcpus) {
 		_kvm_err(kd, kd->program, "cannot read pcpu chunk");
 		return (-1);
 	}
@@ -407,8 +422,8 @@
 			return (NULL);
 	}
 
-	if (cpu < 0 ||  cpu > vm->vm_maxcpus)
+	if (cpu < 0 || cpu > vm->vm_maxcpus)
 		_kvm_err(kd, kd->program, "
 		return (NULL);	/* EDOOFUS actually */
-	return (&vm->pcpu[cpu]);
+	return ((struct pcpu *)&vm->pcpu[cpu * vm->pcpu_recsize]);
 }