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x86/insn: Add insn_get_modrm_reg_off()

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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
This commit is contained in:
Joerg Roedel 2020-09-07 15:15:11 +02:00 committed by Borislav Petkov
parent 172639d799
commit 7af1bd822d
2 changed files with 24 additions and 0 deletions
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1
arch/x86/include/asm/insn-eval.h
View file

@ -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,

23
arch/x86/lib/insn-eval.c
View file

@ -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.