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    SubjectRe: [v3 PATCH 04/10] x86/insn-kernel: Add a function to obtain register offset in ModRM
    On Wed, 25 Jan 2017 12:23:47 -0800
    Ricardo Neri <ricardo.neri-calderon@linux.intel.com> wrote:

    > The function insn_get_reg_offset requires a type to indicate whether
    > the returned offset is that given by by the ModRM or the SIB byte.
    > Callers of this function would need the definition of the type struct.
    > This is not needed. Instead, auxiliary functions can be defined for
    > this purpose.
    >
    > When the operand is a register, the emulation code for User-Mode
    > Instruction Prevention needs to know the offset of the register indicated
    > in the r/m part of the ModRM byte. Thus, start by adding an auxiliary
    > function for this purpose.

    Hmm, why wouldn't you just rename it to insn_get_reg_offset() and export it?

    Thank you,

    >
    > 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-kernel.h | 1 +
    > arch/x86/lib/insn-kernel.c | 5 +++++
    > 2 files changed, 6 insertions(+)
    >
    > diff --git a/arch/x86/include/asm/insn-kernel.h b/arch/x86/include/asm/insn-kernel.h
    > index aef416a..3f34649 100644
    > --- a/arch/x86/include/asm/insn-kernel.h
    > +++ b/arch/x86/include/asm/insn-kernel.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_reg_offset_rm(struct insn *insn, struct pt_regs *regs);
    >
    > #endif /* _ASM_X86_INSN_KERNEL_H */
    > diff --git a/arch/x86/lib/insn-kernel.c b/arch/x86/lib/insn-kernel.c
    > index 8072abe..267cab4 100644
    > --- a/arch/x86/lib/insn-kernel.c
    > +++ b/arch/x86/lib/insn-kernel.c
    > @@ -95,6 +95,11 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
    > return regoff[regno];
    > }
    >
    > +int insn_get_reg_offset_rm(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
    >


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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