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[PATCH v7 08/26] x86/insn-eval: Add a utility function to get register offsets

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The function get_reg_offset() returns the offset to the register the
argument specifies as indicated in an enumeration of type offset. Callers
of this function would need the definition of such enumeration. This is
not needed. Instead, add helper functions for this purpose. These functions
are useful in cases when, for instance, the caller needs to decide whether
the operand is a register or a memory location by looking at the rm part
of the ModRM byte. As of now, this is the only helper function that is
needed.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
 arch/x86/include/asm/insn-eval.h |  1 +
 arch/x86/lib/insn-eval.c         | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
index 5cab1b1..7e8c963 100644
--- a/arch/x86/include/asm/insn-eval.h
+++ b/arch/x86/include/asm/insn-eval.h
@@ -12,5 +12,6 @@
 #include <asm/ptrace.h>
 
 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);
 
 #endif /* _ASM_X86_INSN_EVAL_H */
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 182e2ae..8b16761 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -97,6 +97,21 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
 	return regoff[regno];
 }
 
+/**
+ * insn_get_reg_offset_modrm_rm() - Obtain register in r/m part of ModRM byte
+ * @insn:	Instruction structure containing the ModRM byte
+ * @regs:	Structure with register values as seen when entering kernel mode
+ *
+ * Return: The register indicated by the r/m part of the ModRM byte. The
+ * register is obtained as an offset from the base of pt_regs. In specific
+ * cases, the returned value can be -EDOM to indicate that the particular value
+ * of ModRM does not refer to a register and shall be ignored.
+ */
+int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
+{
+	return get_reg_offset(insn, regs, REG_TYPE_RM);
+}
+
 /*
  * return the address being referenced be instruction
  * for rm=3 returning the content of the rm reg
-- 
2.9.3

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[PATCH v7 00/26] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 26/26] selftests/x86: Add tests for instruction str and sldt Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 25/26] selftests/x86: Add tests for User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 13/26] x86/insn-eval: Add function to get default params of code segment Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 10/26] x86/insn-eval: Add utility functions to get segment selector Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 24/26] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 20/26] x86/cpufeature: Add User-Mode Instruction Prevention definitions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
    Re: [PATCH v7 20/26] x86/cpufeature: Add User-Mode Instruction  Prevention definitions Paolo Bonzini <pbonzini@redhat.com> - 2017-05-06 11:10 +0200
      Re: [PATCH v7 20/26] x86/cpufeature: Add User-Mode Instruction  Prevention definitions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-11 05:30 +0200
  [PATCH v7 12/26] x86/insn-eval: Add utility functions to get segment descriptor base address and limit Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 14/26] x86/insn-eval: Indicate a 32-bit displacement if ModRM.mod is 0 and ModRM.rm is 5 Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 16/26] x86/insn-eval: Support both signed 32-bit and 64-bit effective addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 03/26] x86/mpx: Use signed variables to compute effective addresses Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:20 +0200
  [PATCH v7 06/26] x86/mpx, x86/insn: Relocate insn util functions to a new insn-eval file Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 19/26] x86/insn-eval: Add wrapper function for 16-bit and 32-bit address encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 15/26] x86/insn-eval: Incorporate segment base and limit in linear address computation Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 05/26] x86/mpx: Do not use SIB.base if its value is 101b and ModRM.mod = 0 Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 09/26] x86/insn-eval: Add utility function to identify string instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 22/26] x86/umip: Force a page fault when unable to copy emulated result to user Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 04/26] x86/mpx: Do not use SIB.index if its value is 100b and ModRM.mod is not 11b Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 07/26] x86/insn-eval: Do not BUG on invalid register type Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 11/26] x86/insn-eval: Add utility function to get segment descriptor Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 17/26] x86/insn-eval: Handle 32-bit address encodings in virtual-8086 mode Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 08/26] x86/insn-eval: Add a utility function to get register offsets Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 18/26] x86/insn-eval: Add support to resolve 16-bit addressing encodings Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200
  [PATCH v7 21/26] x86: Add emulation code for UMIP instructions Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2017-05-05 20:30 +0200

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