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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 <mingo@elte.hu> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: yrl.pp-manager.tt@hitachi.com Link: http://lkml.kernel.org/r/20111205120539.15475.91428.stgit@cloud Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1056c3e916
commit
130b78b2bf
2 changed files with 11 additions and 2 deletions
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@ -82,9 +82,16 @@ insn_attr_t inat_get_avx_attribute(insn_byte_t opcode, insn_byte_t vex_m,
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const insn_attr_t *table;
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if (vex_m > X86_VEX_M_MAX || vex_p > INAT_LSTPFX_MAX)
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return 0;
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table = inat_avx_tables[vex_m][vex_p];
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/* At first, this checks the master table */
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table = inat_avx_tables[vex_m][0];
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if (!table)
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return 0;
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if (!inat_is_group(table[opcode]) && vex_p) {
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/* If this is not a group, get attribute directly */
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table = inat_avx_tables[vex_m][vex_p];
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if (!table)
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return 0;
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}
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return table[opcode];
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}
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@ -202,7 +202,7 @@ void insn_get_opcode(struct insn *insn)
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m = insn_vex_m_bits(insn);
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p = insn_vex_p_bits(insn);
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insn->attr = inat_get_avx_attribute(op, m, p);
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if (!inat_accept_vex(insn->attr))
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if (!inat_accept_vex(insn->attr) && !inat_is_group(insn->attr))
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insn->attr = 0; /* This instruction is bad */
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goto end; /* VEX has only 1 byte for opcode */
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}
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@ -249,6 +249,8 @@ void insn_get_modrm(struct insn *insn)
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pfx = insn_last_prefix(insn);
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insn->attr = inat_get_group_attribute(mod, pfx,
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insn->attr);
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if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
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insn->attr = 0; /* This is bad */
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}
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}
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