Our PV guest patching code assembles chunks of instructions on the fly when it
encounters more complicated instructions to hijack. These instructions need
to live in a section that we don't mark as non-executable, as otherwise we
fault when jumping there.
Right now we put it into the .bss section where it automatically gets marked
as non-executable. Add a check to the NX setting function to ensure that we
leave these particular pages executable.
Signed-off-by: Alexander Graf <agraf@xxxxxxx>
---
arch/powerpc/include/asm/sections.h | 11 +++++++++++
arch/powerpc/kernel/kvm.c | 2 +-
arch/powerpc/mm/hash_utils_64.c | 4 ++++
3 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index d0e784e..5217903 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -39,6 +39,17 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
(unsigned long)_stext < end;
}
+static inline int overlaps_kvm_tmp(unsigned long start, unsigned long end)
+{
+#ifdef CONFIG_KVM_GUEST
+ extern char kvm_tmp[];
+ return start < (unsigned long)kvm_tmp &&
+ (unsigned long)&kvm_tmp[1024 * 1024] < end;
+#else
+ return 0;
+#endif
+}
+
#undef dereference_function_descriptor
static inline void *dereference_function_descriptor(void *ptr)
{
diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 6a01752..dd8695f 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c
@@ -74,7 +74,7 @@
#define KVM_INST_MTSRIN 0x7c0001e4
static bool kvm_patching_worked = true;
-static char kvm_tmp[1024 * 1024];
+char kvm_tmp[1024 * 1024];
static int kvm_tmp_index;
static inline void kvm_patch_ins(u32 *inst, u32 new_inst)
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index d766d6e..06ba83b 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -207,6 +207,10 @@ int htab_bolt_mapping(unsigned long vstart, unsigned long vend,
if (overlaps_kernel_text(vaddr, vaddr + step))
tprot &= ~HPTE_R_N;
+ /* Make kvm guest trampolines executable */
+ if (overlaps_kvm_tmp(vaddr, vaddr + step))
+ tprot &= ~HPTE_R_N;
+
/*
* If relocatable, check if it overlaps interrupt vectors that
* are copied down to real 0. For relocatable kernel
--
1.8.1.4
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