From b18db0b80867931f4e3a844400a3c22a4fd2ff57 Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Tue, 29 Apr 2014 12:17:26 +0200 Subject: [PATCH] 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 --- 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 -- 2.7.4