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] xen/x86: Remap text/data/bss with appropriate permissions
Date: Thu, 17 Mar 2016 12:43:15 +0000 [thread overview]
Message-ID: <1458218596-23847-1-git-send-email-andrew.cooper3@citrix.com> (raw)
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>
---
xen/arch/x86/setup.c | 24 ++++++++++++++++++++++++
xen/arch/x86/xen.lds.S | 16 ++++++++++++++++
2 files changed, 40 insertions(+)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index c5c332d..e278a7b 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -529,9 +529,33 @@ static void noinline init_done(void)
}
else
{
+ /* 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);
+
+ /* Free and reuse .init. */
destroy_xen_mappings((unsigned long)&__init_begin,
(unsigned long)&__init_end);
init_xenheap_pages(__pa(__init_begin), __pa(__init_end));
+
+ /* 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)));
}
printk("Freed %ldkB init memory.\n", (long)(__init_end-__init_begin)>>10);
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 961f48f..ab8ba74 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -55,6 +55,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_text_end = .;
@@ -98,6 +100,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_rodata_end = .;
@@ -167,6 +171,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_init_end = .;
@@ -211,6 +217,8 @@ SECTIONS
#ifdef EFI
. = ALIGN(MB(2));
+#else
+ . = ALIGN(PAGE_SIZE);
#endif
__2M_rwdata_end = .;
@@ -269,6 +277,14 @@ 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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next reply other threads:[~2016-03-17 12:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 12:43 Andrew Cooper [this message]
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 ` [PATCH v2] " Andrew Cooper
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