[Xen-devel] [PATCH v2 5/4] xen: arm: ensure that the boot code is <4K in size

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

This avoids having to deal with the 1:1 boot mapping crossing a
section or page boundary.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/arch/arm/arm32/head.S |    3 +++
 xen/arch/arm/arm64/head.S |    3 +++
 xen/arch/arm/xen.lds.S    |    6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index caf7934..b4c3973 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -458,6 +458,9 @@ fail:   PRINT("- Boot failed -\r\n")
 1:      wfe
         b     1b
 
+.globl _end_boot
+_end_boot:
+
 /* Copy Xen to new location and switch TTBR
  * r1:r0       ttbr
  * r2          source address
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index f28b74a..a52e2e4 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -487,6 +487,9 @@ fail:   PRINT("- Boot failed -\r\n")
 1:      wfe
         b     1b
 
+.globl _end_boot
+_end_boot:
+
 /* Copy Xen to new location and switch TTBR
  * x0    ttbr
  * x1    source address
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index be55dad..079e085 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -178,3 +178,9 @@ SECTIONS
   .stab.indexstr 0 : { *(.stab.indexstr) }
   .comment 0 : { *(.comment) }
 }
+
+/*
+ * We require that Xen is loaded at a 4K boundary, so this ensures that any
+ * code running on the boot time identity map cannot cross a section boundary.
+ */
+ASSERT( _end_boot - start <= PAGE_SIZE, "Boot code is larger than 4K")
-- 
1.7.10.4




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