From caf520b2c61a35cdb196e850443038d367c10238 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Wed, 14 Dec 2016 11:05:18 +0000 Subject: [PATCH] x86/emul: Simplfy L{ES,DS,SS,FS,GS} handling %ss, %fs and %gs can be calculated by directly masking the opcode. %es and %ds cant, but the calculation isn't hard. Use seg rather than dst.val for storing the calculated segment, which is appropriately typed. Drop the sel local variable entirely and use dst.val instead. The mode_64bit() check can be repositioned and simplified to drop the ext check. Replace opencoding of X86EMUL_OKAY. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- xen/arch/x86/x86_emulate/x86_emulate.c | 32 +++++++++----------------- 1 file changed, 11 insertions(+), 21 deletions(-) diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 6313b57bf8..f69decee10 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -3398,24 +3398,20 @@ x86_emulate( _regs.eip = dst.val; break; - case 0xc4: /* les */ { - unsigned long sel; - dst.val = x86_seg_es; - les: /* dst.val identifies the segment */ - generate_exception_if(mode_64bit() && !ext, EXC_UD); + case 0xc4: /* les */ + case 0xc5: /* lds */ + generate_exception_if(mode_64bit(), EXC_UD); + seg = (b & 1) * 3; /* es = 0, ds = 3 */ + les: generate_exception_if(src.type != OP_MEM, EXC_UD); if ( (rc = read_ulong(src.mem.seg, src.mem.off + src.bytes, - &sel, 2, ctxt, ops)) != 0 ) + &dst.val, 2, ctxt, ops)) != X86EMUL_OKAY ) goto done; - if ( (rc = load_seg(dst.val, sel, 0, NULL, ctxt, ops)) != 0 ) + ASSERT(is_x86_user_segment(seg)); + if ( (rc = load_seg(seg, dst.val, 0, NULL, ctxt, ops)) != X86EMUL_OKAY ) goto done; dst.val = src.val; break; - } - - case 0xc5: /* lds */ - dst.val = x86_seg_ds; - goto les; case 0xc8: /* enter imm16,imm8 */ { uint8_t depth = imm2 & 31; @@ -5274,21 +5270,15 @@ x86_emulate( break; case X86EMUL_OPC(0x0f, 0xb2): /* lss */ - dst.val = x86_seg_ss; + case X86EMUL_OPC(0x0f, 0xb4): /* lfs */ + case X86EMUL_OPC(0x0f, 0xb5): /* lgs */ + seg = b & 7; goto les; case X86EMUL_OPC(0x0f, 0xb3): btr: /* btr */ emulate_2op_SrcV_nobyte("btr", src, dst, _regs.eflags); break; - case X86EMUL_OPC(0x0f, 0xb4): /* lfs */ - dst.val = x86_seg_fs; - goto les; - - case X86EMUL_OPC(0x0f, 0xb5): /* lgs */ - dst.val = x86_seg_gs; - goto les; - case X86EMUL_OPC(0x0f, 0xb6): /* movzx rm8,r{16,32,64} */ /* Recompute DstReg as we may have decoded AH/BH/CH/DH. */ dst.reg = decode_register(modrm_reg, &_regs, 0); -- 2.30.2