From 130b78b2bf16d5d89091db38374faef896360cf9 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 5 Dec 2011 21:05:39 +0900 Subject: [PATCH] x86: Fix instruction decoder to handle grouped AVX instructions For reducing memory usage of attribute table, x86 instruction decoder puts "Group" attribute only on "no-last-prefix" attribute table (same as vex_p == 0 case). Thus, the decoder should look no-last-prefix table first, and then only if it is not a group, move on to "with-last-prefix" table (vex_p != 0). However, current implementation, inat_get_avx_attribute() looks with-last-prefix directly. So, when decoding a grouped AVX instruction, the decoder fails to find correct group because there is no "Group" attribute on the table. This ends up with the mis-decoding of instructions, as Ingo reported in http://thread.gmane.org/gmane.linux.kernel/1214103 This patch fixes it to check no-last-prefix table first even if that is an AVX instruction, and get an attribute from "with last-prefix" table only if that is not a group. Reported-by: Ingo Molnar Signed-off-by: Masami Hiramatsu Cc: "H. Peter Anvin" Cc: yrl.pp-manager.tt@hitachi.com Link: http://lkml.kernel.org/r/20111205120539.15475.91428.stgit@cloud Signed-off-by: Ingo Molnar --- arch/x86/lib/inat.c | 9 ++++++++- arch/x86/lib/insn.c | 4 +++- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/inat.c b/arch/x86/lib/inat.c index 46fc4ee..88ad5fb 100644 --- a/arch/x86/lib/inat.c +++ b/arch/x86/lib/inat.c @@ -82,9 +82,16 @@ insn_attr_t inat_get_avx_attribute(insn_byte_t opcode, insn_byte_t vex_m, const insn_attr_t *table; if (vex_m > X86_VEX_M_MAX || vex_p > INAT_LSTPFX_MAX) return 0; - table = inat_avx_tables[vex_m][vex_p]; + /* At first, this checks the master table */ + table = inat_avx_tables[vex_m][0]; if (!table) return 0; + if (!inat_is_group(table[opcode]) && vex_p) { + /* If this is not a group, get attribute directly */ + table = inat_avx_tables[vex_m][vex_p]; + if (!table) + return 0; + } return table[opcode]; } diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 374562e..5a1f9f3 100644 --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -202,7 +202,7 @@ void insn_get_opcode(struct insn *insn) m = insn_vex_m_bits(insn); p = insn_vex_p_bits(insn); insn->attr = inat_get_avx_attribute(op, m, p); - if (!inat_accept_vex(insn->attr)) + if (!inat_accept_vex(insn->attr) && !inat_is_group(insn->attr)) insn->attr = 0; /* This instruction is bad */ goto end; /* VEX has only 1 byte for opcode */ } @@ -249,6 +249,8 @@ void insn_get_modrm(struct insn *insn) pfx = insn_last_prefix(insn); insn->attr = inat_get_group_attribute(mod, pfx, insn->attr); + if (insn_is_avx(insn) && !inat_accept_vex(insn->attr)) + insn->attr = 0; /* This is bad */ } } -- 2.7.4