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Adapt the OpenBSD hvt tender to the new vmm(4) #600

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Merged
merged 3 commits into from
Sep 23, 2025
Merged

Adapt the OpenBSD hvt tender to the new vmm(4) #600

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f61ebf1
Adapt the OpenBSD hvt tender to the new vmm(4)
omegametabroccolo Jul 27, 2025
6d22f10
Declare host_prot in case we do have VMM_IOC_MPROTECT_EPT
omegametabroccolo Jul 27, 2025
8e6deda
Still be compatible with OpenBSD 7.7
hannesm Sep 23, 2025
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16 changes: 11 additions & 5 deletions tenders/hvt/hvt_openbsd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,9 @@ struct hvt *hvt_init(size_t mem_size)
struct hvt_b *hvb;
struct vm_create_params *vcp;
struct vm_mem_range *vmr;
#if OpenBSD <= 202504
void *p;
#endif

if(geteuid() != 0) {
errno = EPERM;
Expand Down Expand Up @@ -121,6 +123,7 @@ struct hvt *hvt_init(size_t mem_size)
vcp->vcp_memranges[0].vmr_size = mem_size;

vmr = &vcp->vcp_memranges[0];
#ifdef OpenBSD <= 202504
p = mmap(NULL, vmr->vmr_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON, -1, 0);
if (p == MAP_FAILED)
Expand All @@ -129,10 +132,15 @@ struct hvt *hvt_init(size_t mem_size)
vmr->vmr_va = (vaddr_t)p;
hvt->mem = p;
hvt->mem_size = mem_size;
#endif

if (ioctl(hvb->vmd_fd, VMM_IOC_CREATE, vcp) < 0)
err(1, "create vmm ioctl failed - exiting");

#ifdef OpenBSD > 202504
hvt->mem = (uint8_t *)vmr->vmr_va;
hvt->mem_size = mem_size;
#endif
hvb->vcp_id = vcp->vcp_id;
hvb->vcpu_id = 0; // the first and only cpu is at 0

Expand Down Expand Up @@ -175,7 +183,6 @@ int hvt_guest_mprotect(void *t_arg, uint64_t addr_start, uint64_t addr_end,
int prot)
{
struct hvt *hvt = t_arg;
int host_prot, ret;

assert(addr_start <= hvt->mem_size);
assert(addr_end <= hvt->mem_size);
Expand All @@ -186,20 +193,19 @@ int hvt_guest_mprotect(void *t_arg, uint64_t addr_start, uint64_t addr_end,
size_t size = addr_end - addr_start;
assert(size > 0 && size <= hvt->mem_size);

#if defined(VMM_IOC_MPROTECT_EPT)
/*
* Host-side page protections:
*
* Ensure that guest-executable pages are not also executable, but are
* readable in the host.
*/
host_prot = prot;
int host_prot = prot;
host_prot &= ~(PROT_EXEC);
host_prot |= PROT_READ;
if(mprotect(vaddr_start, size, host_prot) == -1)
return -1;

ret = 0;
#if defined(VMM_IOC_MPROTECT_EPT)
/*
* Guest-side page protections:
*/
Expand All @@ -223,5 +229,5 @@ int hvt_guest_mprotect(void *t_arg, uint64_t addr_start, uint64_t addr_end,
err(1, "mprotect ept vmm ioctl failed - exiting");
}
#endif
return ret;
return 0;
}