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x86/xen: stop assuming kernel memory loading order in PVH

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Do not assume that start_info will always be loaded at the highest
memory address, and instead check the position of all the loaded
elements in order to find the last loaded one, and thus a likely safe
place to use as early boot allocation memory space.

Reported by: markj, cperciva
Sponsored by: Citrix Systems R&D
Reviewed by: markj
Differential revision: https://reviews.freebsd.org/D35628
This commit is contained in:
Roger Pau Monné 2022-06-28 17:37:00 +02:00
parent 038405f32f
commit 77cb05db0c
1 changed files with 30 additions and 22 deletions
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52
sys/x86/xen/pv.c
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@ -68,6 +68,7 @@ __FBSDID("$FreeBSD$");
#include <machine/intr_machdep.h>
#include <machine/md_var.h>
#include <machine/metadata.h>
#include <machine/cpu.h>
#include <xen/xen-os.h>
#include <xen/hvm.h>
@ -143,10 +144,36 @@ hammer_time_xen(vm_paddr_t start_info_paddr)
}
/*
* The hvm_start_into structure is always appended after loading
* the kernel and modules.
* Select the higher address to use as physfree: either after
* start_info, after the kernel, after the memory map or after any of
* the modules. We assume enough memory to be available after the
* selected address for the needs of very early memory allocations.
*/
physfree = roundup2(start_info_paddr + PAGE_SIZE, PAGE_SIZE);
physfree = roundup2(start_info_paddr + sizeof(struct hvm_start_info),
PAGE_SIZE);
physfree = MAX(roundup2((vm_paddr_t)_end - KERNBASE, PAGE_SIZE),
physfree);
if (start_info->memmap_paddr != 0)
physfree = MAX(roundup2(start_info->memmap_paddr +
start_info->memmap_entries *
sizeof(struct hvm_memmap_table_entry), PAGE_SIZE),
physfree);
if (start_info->modlist_paddr != 0) {
unsigned int i;
if (start_info->nr_modules == 0) {
xc_printf(
"ERROR: modlist_paddr != 0 but nr_modules == 0\n");
HYPERVISOR_shutdown(SHUTDOWN_crash);
}
mod = (struct hvm_modlist_entry *)
(start_info->modlist_paddr + KERNBASE);
for (i = 0; i < start_info->nr_modules; i++)
physfree = MAX(roundup2(mod[i].paddr + mod[i].size,
PAGE_SIZE), physfree);
}
xatp.domid = DOMID_SELF;
xatp.idx = 0;
@ -168,25 +195,6 @@ hammer_time_xen(vm_paddr_t start_info_paddr)
bzero_early(kenv, PAGE_SIZE);
init_static_kenv(kenv, PAGE_SIZE);
if (start_info->modlist_paddr != 0) {
if (start_info->modlist_paddr >= physfree) {
xc_printf(
"ERROR: unexpected module list memory address\n");
HYPERVISOR_shutdown(SHUTDOWN_crash);
}
if (start_info->nr_modules == 0) {
xc_printf(
"ERROR: modlist_paddr != 0 but nr_modules == 0\n");
HYPERVISOR_shutdown(SHUTDOWN_crash);
}
mod = (struct hvm_modlist_entry *)
(start_info->modlist_paddr + KERNBASE);
if (mod[0].paddr >= physfree) {
xc_printf("ERROR: unexpected module memory address\n");
HYPERVISOR_shutdown(SHUTDOWN_crash);
}
}
/* Set the hooks for early functions that diverge from bare metal */
init_ops = xen_pvh_init_ops;
hvm_start_flags = start_info->flags;