From 1f65958d9c21fd3b461f6b645e7884866313c1f3 Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Mon, 25 May 2015 01:47:23 +0200 Subject: target-s390x: fix MMU index computation The cpu_mmu_index function wrongly looks at PSW P bit to determine the MMU index, while this bit actually only control the use of priviledge instructions. The addressing mode is detected by looking at the PSW ASC bits instead. This used to work more or less correctly up to kernel 3.6 as the kernel was running in primary space and userland in secondary space. Since kernel 3.7 the default is to run the kernel in home space and userland in primary space. While the current QEMU code seems to work it open some security issues, like accessing the lowcore memory in R/W mode from a userspace process once it has been accessed by the kernel (it is then cached by the QEMU TLB). At the same time change the MMU_USER_IDX value so that it matches the value used in recent kernels. Signed-off-by: Aurelien Jarno Signed-off-by: Alexander Graf --- target-s390x/cpu.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'target-s390x') diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h index 3140f75..adb9a84 100644 --- a/target-s390x/cpu.h +++ b/target-s390x/cpu.h @@ -48,7 +48,7 @@ #define MMU_MODE1_SUFFIX _secondary #define MMU_MODE2_SUFFIX _home -#define MMU_USER_IDX 1 +#define MMU_USER_IDX 0 #define MAX_EXT_QUEUE 16 #define MAX_IO_QUEUE 16 @@ -304,11 +304,18 @@ static inline CPU_DoubleU *get_freg(CPUS390XState *cs, int nr) static inline int cpu_mmu_index (CPUS390XState *env) { - if (env->psw.mask & PSW_MASK_PSTATE) { + switch (env->psw.mask & PSW_MASK_ASC) { + case PSW_ASC_PRIMARY: + return 0; + case PSW_ASC_SECONDARY: return 1; + case PSW_ASC_HOME: + return 2; + case PSW_ASC_ACCREG: + /* Fallthrough: access register mode is not yet supported */ + default: + abort(); } - - return 0; } static inline void cpu_get_tb_cpu_state(CPUS390XState* env, target_ulong *pc, -- cgit v1.1