x86/insn: Add insn_get_modrm_reg_off()
Add a function to the instruction decoder which returns the pt_regs
offset of the register specified in the reg field of the modrm byte.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-11-joro@8bytes.org
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 2323c85..f20942c 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -20,6 +20,7 @@
enum reg_type {
REG_TYPE_RM = 0,
+ REG_TYPE_REG,
REG_TYPE_INDEX,
REG_TYPE_BASE,
};
@@ -439,6 +440,13 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
regno += 8;
break;
+ case REG_TYPE_REG:
+ regno = X86_MODRM_REG(insn->modrm.value);
+
+ if (X86_REX_R(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
case REG_TYPE_INDEX:
regno = X86_SIB_INDEX(insn->sib.value);
if (X86_REX_X(insn->rex_prefix.value))
@@ -808,6 +816,21 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
}
/**
+ * insn_get_modrm_reg_off() - Obtain register in reg part of the ModRM byte
+ * @insn: Instruction containing the ModRM byte
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * Returns:
+ *
+ * The register indicated by the reg part of the ModRM byte. The
+ * register is obtained as an offset from the base of pt_regs.
+ */
+int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs)
+{
+ return get_reg_offset(insn, regs, REG_TYPE_REG);
+}
+
+/**
* get_seg_base_limit() - obtain base address and limit of a segment
* @insn: Instruction. Must be valid.
* @regs: Register values as seen when entering kernel mode