[tip: x86/misc] x86/insn-eval: Introduce insn_get_modrm_reg_ptr()

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/misc branch of tip:

Commit-ID:     d5ec1877df6da6a14bbc353aff50689528930dd2
Gitweb:        https://git.kernel.org/tip/d5ec1877df6da6a14bbc353aff50689528930dd2
Author:        Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
AuthorDate:    Tue, 30 Nov 2021 21:49:31 +03:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Tue, 30 Nov 2021 14:53:04 -08:00

x86/insn-eval: Introduce insn_get_modrm_reg_ptr()

The helper returns a pointer to the register indicated by
ModRM byte.

It's going to replace vc_insn_get_reg() in the SEV MMIO
implementation. TDX MMIO implementation will also use it.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Tested-by: Joerg Roedel <jroedel@xxxxxxx>
Acked-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Link: https://lkml.kernel.org/r/20211130184933.31005-3-kirill.shutemov@xxxxxxxxxxxxxxx
---
 arch/x86/include/asm/insn-eval.h |  1 +
 arch/x86/lib/insn-eval.c         | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index 4ec3613..33ae404 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -19,6 +19,7 @@ bool insn_has_rep_prefix(struct insn *insn);
 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_modrm_reg_ptr(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_get_effective_ip(struct pt_regs *regs, unsigned long *ip);
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 1c51e8a..8df6236 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -849,6 +849,26 @@ int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs)
 }
 
 /**
+ * insn_get_modrm_reg_ptr() - Obtain register pointer based on 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 a pointer within pt_regs.
+ */
+unsigned long *insn_get_modrm_reg_ptr(struct insn *insn, struct pt_regs *regs)
+{
+	int offset;
+
+	offset = insn_get_modrm_reg_off(insn, regs);
+	if (offset < 0)
+		return NULL;
+	return (void *)regs + offset;
+}
+
+/**
  * 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