Commit 7af1bd82 authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
Browse files

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: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-11-joro@8bytes.org
parent 172639d7

arch/x86/include/asm/insn-eval.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

arch/x86/lib/insn-eval.c

+23 −0
Original line number Diff line number Diff line
@@ -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))
@@ -807,6 +815,21 @@ 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.

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