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libkvm/kvm_amd64: account for relocatable kernels

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amd64 kernels don't have to be loaded at 2M physical anymore, they can
be anywhere in the lower 4G of the physical address space. The kernel
now provides its physical address in an ELF section in the dump, so
account for it.

Reviewed by: markj
Approved by: imp (mentor)
Pull Request: https://github.com/freebsd/freebsd-src/pull/1706
This commit is contained in:
Ahmad Khalifa 2025-05-21 23:41:15 +03:00
parent 2941822561
commit 308659acbf
1 changed files with 37 additions and 9 deletions
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46
lib/libkvm/kvm_amd64.c
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@ -109,8 +109,9 @@ _amd64_initvtop(kvm_t *kd)
{
struct kvm_nlist nl[2];
amd64_physaddr_t pa;
kvaddr_t kernbase;
kvaddr_t kernbase, kernphys;
amd64_pml4e_t *PML4;
int found = 0;
kd->vmst = (struct vmstate *)_kvm_malloc(kd, sizeof(*kd->vmst));
if (kd->vmst == NULL) {
@ -123,16 +124,43 @@ _amd64_initvtop(kvm_t *kd)
if (_kvm_read_core_phdrs(kd, &kd->vmst->phnum,
&kd->vmst->phdr) == -1)
return (-1);
for (size_t i = 0; i < kd->vmst->phnum; i++) {
if (kd->vmst->phdr[i].p_type == PT_DUMP_DELTA) {
/* Account for the 2M hole at KERNBASE. */
kernphys = kd->vmst->phdr[i].p_paddr -
kd->vmst->phdr[i].p_align;
kernbase = kd->vmst->phdr[i].p_vaddr;
found = 1;
break;
}
}
}
nl[0].n_name = "kernbase";
nl[1].n_name = 0;
if (found == 0) {
nl[0].n_name = "kernbase";
nl[1].n_name = 0;
if (kvm_nlist2(kd, nl) != 0) {
_kvm_err(kd, kd->program, "bad namelist - no kernbase");
return (-1);
if (kvm_nlist2(kd, nl) != 0) {
_kvm_err(kd, kd->program, "bad namelist - no kernbase");
return (-1);
}
nl[0].n_name = "kernphys";
nl[1].n_name = 0;
/* XXX
* Relocatable kernels can still be loaded at 2M.
*/
if (kvm_nlist2(kd, nl) != 1) {
_kvm_err(kd, kd->program, "cannot determine kernphys");
return (-1);
}
kernphys = 0;
kernbase = nl[0].n_value;
}
kernbase = nl[0].n_value;
nl[0].n_name = "KPML4phys";
nl[1].n_name = 0;
@ -141,8 +169,8 @@ _amd64_initvtop(kvm_t *kd)
_kvm_err(kd, kd->program, "bad namelist - no KPML4phys");
return (-1);
}
if (kvm_read2(kd, (nl[0].n_value - kernbase), &pa, sizeof(pa)) !=
sizeof(pa)) {
if (kvm_read2(kd, (nl[0].n_value - kernbase + kernphys), &pa,
sizeof(pa)) != sizeof(pa)) {
_kvm_err(kd, kd->program, "cannot read KPML4phys");
return (-1);
}