From: Masami Hiramatsu mhiramat@kernel.org
commit 4d65adfcd1196818659d3bd9b42dccab291e1751 upstream
Decode Xen and KVM's emulate-prefix signature by x86 insn decoder. It is called "prefix" but actually not x86 instruction prefix, so this adds insn.emulate_prefix_size field instead of reusing insn.prefixes.
If x86 decoder finds a special sequence of instructions of XEN_EMULATE_PREFIX and 'ud2a; .ascii "kvm"', it just counts the length, set insn.emulate_prefix_size and fold it with the next instruction. In other words, the signature and the next instruction is treated as a single instruction.
Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Josh Poimboeuf jpoimboe@redhat.com Cc: Juergen Gross jgross@suse.com Cc: x86@kernel.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Ingo Molnar mingo@kernel.org Cc: Stefano Stabellini sstabellini@kernel.org Cc: Andrew Cooper andrew.cooper3@citrix.com Cc: Borislav Petkov bp@alien8.de Cc: xen-devel@lists.xenproject.org Cc: Randy Dunlap rdunlap@infradead.org Link: https://lkml.kernel.org/r/156777564986.25081.4964537658500952557.stgit@devno... [mheyne: resolved contextual conflict in tools/objtools/sync-check.sh] Signed-off-by: Maximilian Heyne mheyne@amazon.de Cc: stable@vger.kernel.org # 5.4.x --- arch/x86/include/asm/insn.h | 6 ++++ arch/x86/lib/insn.c | 34 +++++++++++++++++++++ tools/arch/x86/include/asm/emulate_prefix.h | 14 +++++++++ tools/arch/x86/include/asm/insn.h | 6 ++++ tools/arch/x86/lib/insn.c | 34 +++++++++++++++++++++ tools/objtool/sync-check.sh | 3 +- tools/perf/check-headers.sh | 3 +- 7 files changed, 98 insertions(+), 2 deletions(-) create mode 100644 tools/arch/x86/include/asm/emulate_prefix.h
diff --git a/arch/x86/include/asm/insn.h b/arch/x86/include/asm/insn.h index a51ffeea6d87..a8c3d284fa46 100644 --- a/arch/x86/include/asm/insn.h +++ b/arch/x86/include/asm/insn.h @@ -45,6 +45,7 @@ struct insn { struct insn_field immediate2; /* for 64bit imm or seg16 */ };
+ int emulate_prefix_size; insn_attr_t attr; unsigned char opnd_bytes; unsigned char addr_bytes; @@ -128,6 +129,11 @@ static inline int insn_is_evex(struct insn *insn) return (insn->vex_prefix.nbytes == 4); }
+static inline int insn_has_emulate_prefix(struct insn *insn) +{ + return !!insn->emulate_prefix_size; +} + /* Ensure this instruction is decoded completely */ static inline int insn_complete(struct insn *insn) { diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 0b5862ba6a75..404279563891 100644 --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -13,6 +13,8 @@ #include <asm/inat.h> #include <asm/insn.h>
+#include <asm/emulate_prefix.h> + /* Verify next sizeof(t) bytes can be on the same instruction */ #define validate_next(t, insn, n) \ ((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr) @@ -58,6 +60,36 @@ void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64) insn->addr_bytes = 4; }
+static const insn_byte_t xen_prefix[] = { __XEN_EMULATE_PREFIX }; +static const insn_byte_t kvm_prefix[] = { __KVM_EMULATE_PREFIX }; + +static int __insn_get_emulate_prefix(struct insn *insn, + const insn_byte_t *prefix, size_t len) +{ + size_t i; + + for (i = 0; i < len; i++) { + if (peek_nbyte_next(insn_byte_t, insn, i) != prefix[i]) + goto err_out; + } + + insn->emulate_prefix_size = len; + insn->next_byte += len; + + return 1; + +err_out: + return 0; +} + +static void insn_get_emulate_prefix(struct insn *insn) +{ + if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix))) + return; + + __insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix)); +} + /** * insn_get_prefixes - scan x86 instruction prefix bytes * @insn: &struct insn containing instruction @@ -76,6 +108,8 @@ void insn_get_prefixes(struct insn *insn) if (prefixes->got) return;
+ insn_get_emulate_prefix(insn); + nb = 0; lb = 0; b = peek_next(insn_byte_t, insn); diff --git a/tools/arch/x86/include/asm/emulate_prefix.h b/tools/arch/x86/include/asm/emulate_prefix.h new file mode 100644 index 000000000000..70f5b98a5286 --- /dev/null +++ b/tools/arch/x86/include/asm/emulate_prefix.h @@ -0,0 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_EMULATE_PREFIX_H +#define _ASM_X86_EMULATE_PREFIX_H + +/* + * Virt escape sequences to trigger instruction emulation; + * ideally these would decode to 'whole' instruction and not destroy + * the instruction stream; sadly this is not true for the 'kvm' one :/ + */ + +#define __XEN_EMULATE_PREFIX 0x0f,0x0b,0x78,0x65,0x6e /* ud2 ; .ascii "xen" */ +#define __KVM_EMULATE_PREFIX 0x0f,0x0b,0x6b,0x76,0x6d /* ud2 ; .ascii "kvm" */ + +#endif diff --git a/tools/arch/x86/include/asm/insn.h b/tools/arch/x86/include/asm/insn.h index d7f0ae8f3c44..52c6262e6bfd 100644 --- a/tools/arch/x86/include/asm/insn.h +++ b/tools/arch/x86/include/asm/insn.h @@ -45,6 +45,7 @@ struct insn { struct insn_field immediate2; /* for 64bit imm or seg16 */ };
+ int emulate_prefix_size; insn_attr_t attr; unsigned char opnd_bytes; unsigned char addr_bytes; @@ -128,6 +129,11 @@ static inline int insn_is_evex(struct insn *insn) return (insn->vex_prefix.nbytes == 4); }
+static inline int insn_has_emulate_prefix(struct insn *insn) +{ + return !!insn->emulate_prefix_size; +} + /* Ensure this instruction is decoded completely */ static inline int insn_complete(struct insn *insn) { diff --git a/tools/arch/x86/lib/insn.c b/tools/arch/x86/lib/insn.c index 79e048f1d902..0151dfc6da61 100644 --- a/tools/arch/x86/lib/insn.c +++ b/tools/arch/x86/lib/insn.c @@ -13,6 +13,8 @@ #include "../include/asm/inat.h" #include "../include/asm/insn.h"
+#include "../include/asm/emulate_prefix.h" + /* Verify next sizeof(t) bytes can be on the same instruction */ #define validate_next(t, insn, n) \ ((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr) @@ -58,6 +60,36 @@ void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64) insn->addr_bytes = 4; }
+static const insn_byte_t xen_prefix[] = { __XEN_EMULATE_PREFIX }; +static const insn_byte_t kvm_prefix[] = { __KVM_EMULATE_PREFIX }; + +static int __insn_get_emulate_prefix(struct insn *insn, + const insn_byte_t *prefix, size_t len) +{ + size_t i; + + for (i = 0; i < len; i++) { + if (peek_nbyte_next(insn_byte_t, insn, i) != prefix[i]) + goto err_out; + } + + insn->emulate_prefix_size = len; + insn->next_byte += len; + + return 1; + +err_out: + return 0; +} + +static void insn_get_emulate_prefix(struct insn *insn) +{ + if (__insn_get_emulate_prefix(insn, xen_prefix, sizeof(xen_prefix))) + return; + + __insn_get_emulate_prefix(insn, kvm_prefix, sizeof(kvm_prefix)); +} + /** * insn_get_prefixes - scan x86 instruction prefix bytes * @insn: &struct insn containing instruction @@ -76,6 +108,8 @@ void insn_get_prefixes(struct insn *insn) if (prefixes->got) return;
+ insn_get_emulate_prefix(insn); + nb = 0; lb = 0; b = peek_next(insn_byte_t, insn); diff --git a/tools/objtool/sync-check.sh b/tools/objtool/sync-check.sh index c3ae1e8ae119..2a1261bfbb62 100755 --- a/tools/objtool/sync-check.sh +++ b/tools/objtool/sync-check.sh @@ -4,6 +4,7 @@ FILES=' arch/x86/include/asm/inat_types.h arch/x86/include/asm/orc_types.h +arch/x86/include/asm/emulate_prefix.h arch/x86/lib/x86-opcode-map.txt arch/x86/tools/gen-insn-attr-x86.awk ' @@ -46,4 +47,4 @@ done check arch/x86/include/asm/inat.h '-I "^#include ["<](asm/)*inat_types.h[">]"' check arch/x86/include/asm/insn.h '-I "^#include ["<](asm/)*inat.h[">]"' check arch/x86/lib/inat.c '-I "^#include ["<](../include/)*asm/insn.h[">]"' -check arch/x86/lib/insn.c '-I "^#include ["<](../include/)*asm/in(at|sn).h[">]"' +check arch/x86/lib/insn.c '-I "^#include ["<](../include/)*asm/in(at|sn).h[">]" -I "^#include ["<](../include/)*asm/emulate_prefix.h[">]"' diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh index cea13cb987d0..499235a41162 100755 --- a/tools/perf/check-headers.sh +++ b/tools/perf/check-headers.sh @@ -28,6 +28,7 @@ arch/x86/include/asm/disabled-features.h arch/x86/include/asm/required-features.h arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/inat_types.h +arch/x86/include/asm/emulate_prefix.h arch/x86/include/uapi/asm/prctl.h arch/x86/lib/x86-opcode-map.txt arch/x86/tools/gen-insn-attr-x86.awk @@ -116,7 +117,7 @@ check lib/ctype.c '-I "^EXPORT_SYMBOL" -I "^#include <linux/export.h>" -B check arch/x86/include/asm/inat.h '-I "^#include ["<](asm/)*inat_types.h[">]"' check arch/x86/include/asm/insn.h '-I "^#include ["<](asm/)*inat.h[">]"' check arch/x86/lib/inat.c '-I "^#include ["<](../include/)*asm/insn.h[">]"' -check arch/x86/lib/insn.c '-I "^#include ["<](../include/)*asm/in(at|sn).h[">]"' +check arch/x86/lib/insn.c '-I "^#include ["<](../include/)*asm/in(at|sn).h[">]" -I "^#include ["<](../include/)*asm/emulate_prefix.h[">]"'
# diff non-symmetric files check_2 tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl