This function returns the default values of the address and operand sizes as specified in the segment descriptor. This information is determined from the D and L bits. Hence, it can be used for both IA-32e 64-bit and 32-bit legacy modes. For virtual-8086 mode, the default address and operand sizes are always 2 bytes. The D bit is only meaningful for code segments. Thus, these functions always use the code segment selector contained in regs. Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Adam Buchbinder <adam.buchbinder@xxxxxxxxx> Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx> Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx> Cc: Qiaowei Ren <qiaowei.ren@xxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Thomas Garnier <thgarnie@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Ravi V. Shankar <ravi.v.shankar@xxxxxxxxx> Cc: x86@xxxxxxxxxx Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> --- arch/x86/include/asm/insn-eval.h | 6 ++++ arch/x86/lib/insn-eval.c | 65 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 7f3c7fe..9ed1c88 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -11,9 +11,15 @@ #include <linux/err.h> #include <asm/ptrace.h> +struct insn_code_seg_defaults { + unsigned char address_bytes; + unsigned char operand_bytes; +}; + void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs); int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs); unsigned long insn_get_seg_base(struct pt_regs *regs, struct insn *insn, int regoff); +struct insn_code_seg_defaults insn_get_code_seg_defaults(struct pt_regs *regs); #endif /* _ASM_X86_INSN_EVAL_H */ diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index c77ed80..693e5a8 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -603,6 +603,71 @@ static unsigned long get_seg_limit(struct pt_regs *regs, struct insn *insn, } /** + * insn_get_code_seg_defaults() - Obtain code segment default parameters + * @regs: Structure with register values as seen when entering kernel mode + * + * Obtain the default parameters of the code segment: address and operand sizes. + * The code segment is obtained from the selector contained in the CS register + * in regs. In protected mode, the default address is determined by inspecting + * the L and D bits of the segment descriptor. In virtual-8086 mode, the default + * is always two bytes for both address and operand sizes. + * + * Return: A populated insn_code_seg_defaults structure on success. The + * structure contains only zeros on failure. + */ +struct insn_code_seg_defaults insn_get_code_seg_defaults(struct pt_regs *regs) +{ + struct desc_struct *desc; + struct insn_code_seg_defaults defs; + unsigned short sel; + /* + * The most significant byte of AR_TYPE_MASK determines whether a + * segment contains data or code. + */ + unsigned int type_mask = AR_TYPE_MASK & (1 << 11); + + memset(&defs, 0, sizeof(defs)); + + if (v8086_mode(regs)) { + defs.address_bytes = 2; + defs.operand_bytes = 2; + return defs; + } + + sel = (unsigned short)regs->cs; + + desc = get_desc(sel); + if (!desc) + return defs; + + /* if data segment, return */ + if (!(desc->b & type_mask)) + return defs; + + switch ((desc->l << 1) | desc->d) { + case 0: /* Legacy mode. CS.L=0, CS.D=0 */ + defs.address_bytes = 2; + defs.operand_bytes = 2; + break; + case 1: /* Legacy mode. CS.L=0, CS.D=1 */ + defs.address_bytes = 4; + defs.operand_bytes = 4; + break; + case 2: /* IA-32e 64-bit mode. CS.L=1, CS.D=0 */ + defs.address_bytes = 8; + defs.operand_bytes = 4; + break; + case 3: /* Invalid setting. CS.L=1, CS.D=1 */ + /* fall through */ + default: + defs.address_bytes = 0; + defs.operand_bytes = 0; + } + + return defs; +} + +/** * insn_get_reg_offset_modrm_rm() - Obtain register in r/m part of ModRM byte * @insn: Instruction structure containing the ModRM byte * @regs: Structure with register values as seen when entering kernel mode -- 2.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-msdos" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html