From 9a46833c54fd320afd3836c0e51ade82e4bc6f96 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 29 Aug 2019 10:01:55 +0900 Subject: [PATCH] x86: xen: insn: Decode XEN_EMULATE_PREFIX correctly Add XEN_EMULATE_PREFIX prefix support to x86 insn decoder. This treats a special sequence of instructions of XEN_EMULATE_PREFIX as a prefix bytes in x86 insn decoder only if CONFIG_XEN_PVHVM=y. Note that this prefix is treated as just a dummy code. Reported-by: Josh Poimboeuf Signed-off-by: Masami Hiramatsu --- arch/x86/include/asm/xen/interface.h | 8 +++++-- arch/x86/lib/insn.c | 35 ++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/xen/interface.h b/arch/x86/include/asm/xen/interface.h index 62ca03ef5c65..fbee520b1f07 100644 --- a/arch/x86/include/asm/xen/interface.h +++ b/arch/x86/include/asm/xen/interface.h @@ -27,6 +27,8 @@ #ifndef _ASM_X86_XEN_INTERFACE_H #define _ASM_X86_XEN_INTERFACE_H +#include + /* * XEN_GUEST_HANDLE represents a guest pointer, when passed as a field * in a struct in memory. @@ -379,11 +381,13 @@ struct xen_pmu_arch { * Prefix forces emulation of some non-trapping instructions. * Currently only CPUID. */ +#define __XEN_EMULATE_PREFIX 0x0f,0x0b,0x78,0x65,0x6e +#define __XEN_EMULATE_PREFIX_STR __stringify(__XEN_EMULATE_PREFIX) #ifdef __ASSEMBLY__ -#define XEN_EMULATE_PREFIX .byte 0x0f,0x0b,0x78,0x65,0x6e ; +#define XEN_EMULATE_PREFIX .byte __XEN_EMULATE_PREFIX ; #define XEN_CPUID XEN_EMULATE_PREFIX cpuid #else -#define XEN_EMULATE_PREFIX ".byte 0x0f,0x0b,0x78,0x65,0x6e ; " +#define XEN_EMULATE_PREFIX ".byte " __XEN_EMULATE_PREFIX_STR " ; " #define XEN_CPUID XEN_EMULATE_PREFIX "cpuid" #endif diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 0b5862ba6a75..2401a6fc9509 100644 --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -7,6 +7,9 @@ #ifdef __KERNEL__ #include +#include +/* For special Xen prefix */ +#include #else #include #endif @@ -58,6 +61,34 @@ void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64) insn->addr_bytes = 4; } +#ifdef CONFIG_XEN_PVHVM +static const insn_byte_t xen_prefix[] = { XEN_EMULATE_PREFIX }; + +static int insn_xen_prefix(struct insn *insn, insn_byte_t b) +{ + struct insn_field *prefixes = &insn->prefixes; + int i = 0; + + while (i < ARRAY_SIZE(xen_prefix) && b == xen_prefix[i]) + b = peek_nbyte_next(insn_byte_t, insn, ++i); + + if (unlikely(i == ARRAY_SIZE(xen_prefix))) { + memcpy(prefixes->bytes, xen_prefix, 3); + prefixes->bytes[3] = xen_prefix[ARRAY_SIZE(xen_prefix) - 1]; + prefixes->nbytes = ARRAY_SIZE(xen_prefix); + insn->next_byte += prefixes->nbytes; + prefixes->got = 1; + + return 1; + } + +err_out: + return 0; +} +#else +#define insn_xen_prefix(insn,b) (0) +#endif + /** * insn_get_prefixes - scan x86 instruction prefix bytes * @insn: &struct insn containing instruction @@ -79,6 +110,10 @@ void insn_get_prefixes(struct insn *insn) nb = 0; lb = 0; b = peek_next(insn_byte_t, insn); + + if (insn_xen_prefix(insn, b)) + return; + attr = inat_get_opcode_attribute(b); while (inat_is_legacy_prefix(attr)) { /* Skip if same prefix */ -- 2.20.1