KVM guest: Make pv trampoline code executable

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@suse.de>

diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index d0e784e0ff484f0053f807e081a4c89fec13dee6..52179033067262f8f107be29c16b1fba6b8d4cee 100644 (file)
--- 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 6a0175297b0d8e92495ce97e7274ecba72fcb790..dd8695f6cb6d2c6de9bca80b073f4f40013cdeef 100644 (file)
--- 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 d766d6ee33fe6889e5a96b3898f8c47b0050fc14..06ba83b036d3360bb8750b1a869dfcf9e09705d0 100644 (file)
--- 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