From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: [PATCH v2] xen/x86: Remap text/data/bss with appropriate permissions
Date: Fri, 18 Mar 2016 19:49:48 +0000 [thread overview]
Message-ID: <1458330588-14901-1-git-send-email-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <56EACDC102000078000DDF03@prv-mh.provo.novell.com>
c/s cf39362 "x86: use 2M superpages for text/data/bss mappings" served two
purposes; to map the primary code and data with appropriate pagetable
permissions (rather than unilaterally RWX), and to reduce the TLB pressure.
The extra alignment exposed a SYSLinux issue, and was partly reverted by c/s
0b8a172 "x86: partially revert use of 2M mappings for hypervisor image".
This change reinstates the pagetable permission improvements while avoiding
the 2M alignment issue.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
v2:
Move the remapping earlier in the boot sequence. This is where
memguart_init() used to reside, which itself used map_pages_to_xen() on the
full virtual region.
---
xen/arch/x86/setup.c | 31 +++++++++++++++++++++++++++++++
xen/arch/x86/xen.lds.S | 16 ++++++++++++++++
2 files changed, 47 insertions(+)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 1876a28..ee65f55 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1205,6 +1205,37 @@ void __init noreturn __start_xen(unsigned long mbi_p)
~((1UL << L2_PAGETABLE_SHIFT) - 1);
destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + BOOTSTRAP_MAP_BASE);
+ /*
+ * If not using 2M mappings to gain suitable pagetable permissions
+ * directly from the relocation above, remap the code/data
+ * sections with decreased permissions.
+ */
+ if ( !using_2M_mapping() )
+ {
+ /* Mark .text as RX (avoiding the first 2M superpage). */
+ map_pages_to_xen(XEN_VIRT_START + MB(2),
+ PFN_DOWN(__pa(XEN_VIRT_START + MB(2))),
+ PFN_DOWN(__2M_text_end -
+ (const char *)(XEN_VIRT_START + MB(2))),
+ PAGE_HYPERVISOR_RX);
+
+ /* Mark .rodata as RO. */
+ map_pages_to_xen((unsigned long)&__2M_rodata_start,
+ PFN_DOWN(__pa(__2M_rodata_start)),
+ PFN_DOWN(__2M_rodata_end - __2M_rodata_start),
+ PAGE_HYPERVISOR_RO);
+
+ /* Mark .data and .bss as RW. */
+ map_pages_to_xen((unsigned long)&__2M_rwdata_start,
+ PFN_DOWN(__pa(__2M_rwdata_start)),
+ PFN_DOWN(__2M_rwdata_end - __2M_rwdata_start),
+ PAGE_HYPERVISOR_RW);
+
+ /* Drop the remaining mappings in the shattered superpage. */
+ destroy_xen_mappings((unsigned long)&__2M_rwdata_end,
+ ROUNDUP((unsigned long)&__2M_rwdata_end, MB(2)));
+ }
+
nr_pages = 0;
for ( i = 0; i < e820.nr_map; i++ )
if ( e820.map[i].type == E820_RAM )
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index e47771c..5eb825e 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -56,6 +56,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_text_end = .;
@@ -99,6 +101,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_rodata_end = .;
@@ -168,6 +172,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_init_end = .;
@@ -212,6 +218,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_rwdata_end = .;
@@ -270,6 +278,14 @@ ASSERT(IS_ALIGNED(__2M_init_start, MB(2)), "__2M_init_start misaligned")
ASSERT(IS_ALIGNED(__2M_init_end, MB(2)), "__2M_init_end misaligned")
ASSERT(IS_ALIGNED(__2M_rwdata_start, MB(2)), "__2M_rwdata_start misaligned")
ASSERT(IS_ALIGNED(__2M_rwdata_end, MB(2)), "__2M_rwdata_end misaligned")
+#else
+ASSERT(IS_ALIGNED(__2M_text_end, PAGE_SIZE), "__2M_text_end misaligned")
+ASSERT(IS_ALIGNED(__2M_rodata_start, PAGE_SIZE), "__2M_rodata_start misaligned")
+ASSERT(IS_ALIGNED(__2M_rodata_end, PAGE_SIZE), "__2M_rodata_end misaligned")
+ASSERT(IS_ALIGNED(__2M_init_start, PAGE_SIZE), "__2M_init_start misaligned")
+ASSERT(IS_ALIGNED(__2M_init_end, PAGE_SIZE), "__2M_init_end misaligned")
+ASSERT(IS_ALIGNED(__2M_rwdata_start, PAGE_SIZE), "__2M_rwdata_start misaligned")
+ASSERT(IS_ALIGNED(__2M_rwdata_end, PAGE_SIZE), "__2M_rwdata_end misaligned")
#endif
ASSERT(IS_ALIGNED(cpu0_stack, STACK_SIZE), "cpu0_stack misaligned")
--
2.1.4
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prev parent reply other threads:[~2016-03-18 19:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 12:43 [PATCH] xen/x86: Remap text/data/bss with appropriate permissions Andrew Cooper
2016-03-17 12:43 ` [PATCH] DO NOT APPLY - debug keys for inspecting Xen mappings Andrew Cooper
2016-03-17 14:31 ` [PATCH] xen/x86: Remap text/data/bss with appropriate permissions Jan Beulich
2016-03-17 14:44 ` Andrew Cooper
2016-03-17 15:32 ` Jan Beulich
2016-03-17 16:15 ` Andrew Cooper
2016-03-18 7:25 ` Jan Beulich
2016-03-18 19:49 ` Andrew Cooper [this message]
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