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From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: Wei.Chen@arm.com, Henry.Wang@arm.com, Penny.Zheng@arm.com,
	Bertrand.Marquis@arm.com, Julien Grall <jgrall@amazon.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it
Date: Sun, 25 Apr 2021 21:13:11 +0100	[thread overview]
Message-ID: <20210425201318.15447-9-julien@xen.org> (raw)
In-Reply-To: <20210425201318.15447-1-julien@xen.org>

From: Julien Grall <jgrall@amazon.com>

Only the first 2GB of the virtual address space is shared between all
the page-tables on Arm32.

There is a long outstanding TODO in xen_pt_update() stating that the
function is can only work with shared mapping. Nobody has ever called
the function with private mapping, however as we add more callers
there is a risk to mess things up.

Introduce a new define to mark the ened of the shared mappings and use
it in xen_pt_update() to verify if the address is correct.

Note that on Arm64, all the mappings are shared. Some compiler may
complain about an always true check, so the new define is not introduced
for arm64 and the code is protected with an #ifdef.

Signed-off-by: Julien Grall <jgrall@amazon.com>

---
    Changes in v2:
        - New patch
---
 xen/arch/arm/mm.c            | 11 +++++++++--
 xen/include/asm-arm/config.h |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 8fac24d80086..5c17cafff847 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1275,11 +1275,18 @@ static int xen_pt_update(unsigned long virt,
      * For arm32, page-tables are different on each CPUs. Yet, they share
      * some common mappings. It is assumed that only common mappings
      * will be modified with this function.
-     *
-     * XXX: Add a check.
      */
     const mfn_t root = virt_to_mfn(THIS_CPU_PGTABLE);
 
+#ifdef SHARED_VIRT_END
+    if ( virt > SHARED_VIRT_END ||
+         (SHARED_VIRT_END - virt) < nr_mfns )
+    {
+        mm_printk("Trying to map outside of the shared area.\n");
+        return -EINVAL;
+    }
+#endif
+
     /*
      * The hardware was configured to forbid mapping both writeable and
      * executable.
diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h
index c7b77912013e..85d4a510ce8a 100644
--- a/xen/include/asm-arm/config.h
+++ b/xen/include/asm-arm/config.h
@@ -137,6 +137,10 @@
 
 #define XENHEAP_VIRT_START     _AT(vaddr_t,0x40000000)
 #define XENHEAP_VIRT_END       _AT(vaddr_t,0x7fffffff)
+
+/* The first 2GB is always shared between all the page-tables. */
+#define SHARED_VIRT_END        _AT(vaddr_t, 0x7fffffff)
+
 #define DOMHEAP_VIRT_START     _AT(vaddr_t,0x80000000)
 #define DOMHEAP_VIRT_END       _AT(vaddr_t,0xffffffff)
 
-- 
2.17.1



  parent reply	other threads:[~2021-04-25 20:13 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-25 20:13 [PATCH RFCv2 00/15] xen/arm: mm: Remove open-coding mappings Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 01/15] xen/arm: lpae: Rename LPAE_ENTRIES_MASK_GS to LPAE_ENTRY_MASK_GS Julien Grall
2021-05-11 22:12   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 02/15] xen/arm: lpae: Use the generic helpers to defined the Xen PT helpers Julien Grall
2021-05-11 22:26   ` Stefano Stabellini
2021-05-12 14:26     ` Julien Grall
2021-05-12 21:30       ` Stefano Stabellini
2021-05-12 22:16         ` Julien Grall
2021-05-13 22:44           ` Stefano Stabellini
2021-07-03 17:32             ` Julien Grall
2021-07-13 20:53               ` Stefano Stabellini
2021-07-14 17:40                 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 03/15] xen/arm: p2m: Replace level_{orders, masks} arrays with LEVEL_{ORDER, MASK} Julien Grall
2021-05-11 22:33   ` Stefano Stabellini
2021-05-12 14:39     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 04/15] xen/arm: mm: Allow other mapping size in xen_pt_update_entry() Julien Grall
2021-05-11 22:42   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 05/15] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted Julien Grall
2021-05-11 22:51   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 06/15] xen/arm: mm: Don't open-code Xen PT update in remove_early_mappings() Julien Grall
2021-05-11 22:58   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 07/15] xen/arm: mm: Re-implement early_fdt_map() using map_pages_to_xen() Julien Grall
2021-05-12 21:41   ` Stefano Stabellini
2021-05-12 22:18     ` Julien Grall
2021-04-25 20:13 ` Julien Grall [this message]
2021-05-12 22:00   ` [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it Stefano Stabellini
2021-05-12 22:23     ` Julien Grall
2021-05-13 22:32       ` Stefano Stabellini
2021-05-13 22:59         ` Julien Grall
2021-05-14  1:04           ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 09/15] xen/arm32: mm: Re-implement setup_xenheap_mappings() using map_pages_to_xen() Julien Grall
2021-05-12 22:07   ` Stefano Stabellini
2021-05-13 17:55     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap Julien Grall
2021-05-12 22:44   ` Stefano Stabellini
2021-05-13 18:09     ` Julien Grall
2021-05-13 22:27       ` Stefano Stabellini
2021-05-15  8:48         ` Julien Grall
2021-05-18  0:37           ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 11/15] xen/arm: mm: Allow page-table allocation from the boot allocator Julien Grall
2021-05-13 22:58   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 12/15] xen/arm: add Persistent Map (PMAP) infrastructure Julien Grall
2021-04-26  9:41   ` Xia, Hongyan
2021-07-03 17:57     ` Julien Grall
2021-04-28 21:47   ` Wei Liu
2021-05-14 23:25   ` Stefano Stabellini
2021-05-15  8:54     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 13/15] xen/arm: mm: Use the PMAP helpers in xen_{,un}map_table() Julien Grall
2021-05-14 23:35   ` Stefano Stabellini
2021-05-15  9:03     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 14/15] xen/arm: mm: Rework setup_xenheap_mappings() Julien Grall
2021-05-14 23:51   ` Stefano Stabellini
2021-05-15  9:21     ` Julien Grall
2021-05-18  0:50       ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 15/15] xen/arm: mm: Re-implement setup_frame_table_mappings() with map_pages_to_xen() Julien Grall
2021-05-15  0:02   ` Stefano Stabellini
2021-05-15  9:25     ` Julien Grall
2021-05-18  0:51       ` Stefano Stabellini

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