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From c3ff11b11c21777a9b1c616607705f3a7340b391 Mon Sep 17 00:00:00 2001
From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Tue, 2 Apr 2024 16:19:36 +0200
Subject: [PATCH 64/67] x86/livepatch: Relax permissions on rodata too
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
This reinstates the capability to patch .rodata in load/unload hooks, which
was lost when we stopped using CR0.WP=0 to patch.
This turns out to be rather less of a large TODO than I thought at the time.
Fixes: 8676092a0f16 ("x86/livepatch: Fix livepatch application when CET is active")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
master commit: b083b1c393dc8961acf0959b1d2e0ad459985ae3
master date: 2024-03-07 14:24:42 +0000
---
xen/arch/x86/livepatch.c | 4 ++--
xen/common/virtual_region.c | 12 ++++++++++++
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index ee539f001b..4f76127e1f 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -62,7 +62,7 @@ int arch_livepatch_safety_check(void)
int noinline arch_livepatch_quiesce(void)
{
/*
- * Relax perms on .text to be RWX, so we can modify them.
+ * Relax perms on .text/.rodata, so we can modify them.
*
* This relaxes perms globally, but all other CPUs are waiting on us.
*/
@@ -75,7 +75,7 @@ int noinline arch_livepatch_quiesce(void)
void noinline arch_livepatch_revive(void)
{
/*
- * Reinstate perms on .text to be RX. This also cleans out the dirty
+ * Reinstate perms on .text/.rodata. This also cleans out the dirty
* bits, which matters when CET Shstk is active.
*
* The other CPUs waiting for us could in principle have re-walked while
diff --git a/xen/common/virtual_region.c b/xen/common/virtual_region.c
index 9c566f8ec9..aefc08e75f 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -91,9 +91,15 @@ void relax_virtual_region_perms(void)
rcu_read_lock(&rcu_virtual_region_lock);
list_for_each_entry_rcu( region, &virtual_region_list, list )
+ {
modify_xen_mappings_lite((unsigned long)region->text_start,
PAGE_ALIGN((unsigned long)region->text_end),
PAGE_HYPERVISOR_RWX);
+ if ( region->rodata_start )
+ modify_xen_mappings_lite((unsigned long)region->rodata_start,
+ PAGE_ALIGN((unsigned long)region->rodata_end),
+ PAGE_HYPERVISOR_RW);
+ }
rcu_read_unlock(&rcu_virtual_region_lock);
}
@@ -103,9 +109,15 @@ void tighten_virtual_region_perms(void)
rcu_read_lock(&rcu_virtual_region_lock);
list_for_each_entry_rcu( region, &virtual_region_list, list )
+ {
modify_xen_mappings_lite((unsigned long)region->text_start,
PAGE_ALIGN((unsigned long)region->text_end),
PAGE_HYPERVISOR_RX);
+ if ( region->rodata_start )
+ modify_xen_mappings_lite((unsigned long)region->rodata_start,
+ PAGE_ALIGN((unsigned long)region->rodata_end),
+ PAGE_HYPERVISOR_RO);
+ }
rcu_read_unlock(&rcu_virtual_region_lock);
}
#endif /* CONFIG_X86 */
--
2.44.0
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