[PATCH v5 09/75] x86/insn: Add insn_get_modrm_reg_off()

Joerg Roedel
2020-07-24T16:10:18Z

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>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/include/asm/insn-eval.h | 1 +
arch/x86/lib/insn-eval.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index 392b4fe377f9..f748f57f1491 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -17,6 +17,7 @@

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);
+int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs);
unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx);
int insn_get_code_seg_params(struct pt_regs *regs);
int insn_fetch_from_user(struct pt_regs *regs,
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index f52046f90dd3..a8ac5c5e94f0 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,
};
@@ -441,6 +442,13 @@ 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))
@@ -809,6 +817,21 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
return get_reg_offset(insn, regs, REG_TYPE_RM);
}

+/**
+ * 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.
--
2.27.0