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    SubjectRe: [PATCH v8 05/28] x86/mpx: Use signed variables to compute effective addresses
    On Fri, Aug 18, 2017 at 05:27:46PM -0700, Ricardo Neri wrote:
    > Even though memory addresses are unsigned, the operands used to compute the
    > effective address do have a sign. This is true for ModRM.rm, SIB.base,
    > SIB.index as well as the displacement bytes. Thus, signed variables shall
    > be used when computing the effective address from these operands. Once the
    > signed effective address has been computed, it is casted to an unsigned
    > long to determine the linear address.
    >
    > Variables are renamed to better reflect the type of address being
    > computed.
    >
    > Cc: Borislav Petkov <bp@suse.de>
    > Cc: Andy Lutomirski <luto@kernel.org>
    > 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: Peter Zijlstra <peterz@infradead.org>
    > Cc: Nathan Howard <liverlint@gmail.com>
    > Cc: Adan Hawthorn <adanhawthorn@gmail.com>
    > Cc: Joe Perches <joe@perches.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/mm/mpx.c | 20 ++++++++++++++------
    > 1 file changed, 14 insertions(+), 6 deletions(-)

    I think you can simplify this function even more (diff ontop):

    diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
    index 9eec98022510..d0ec5c9b2a57 100644
    --- a/arch/x86/mm/mpx.c
    +++ b/arch/x86/mm/mpx.c
    @@ -139,7 +139,7 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
    static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
    {
    int addr_offset, base_offset, indx_offset;
    - unsigned long linear_addr;
    + unsigned long linear_addr = -1;
    long eff_addr, base, indx;
    insn_byte_t sib;

    @@ -150,18 +150,18 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
    if (X86_MODRM_MOD(insn->modrm.value) == 3) {
    addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
    if (addr_offset < 0)
    - goto out_err;
    + goto out;

    eff_addr = regs_get_register(regs, addr_offset);
    } else {
    if (insn->sib.nbytes) {
    base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
    if (base_offset < 0)
    - goto out_err;
    + goto out;

    indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
    if (indx_offset < 0)
    - goto out_err;
    + goto out;

    base = regs_get_register(regs, base_offset);
    indx = regs_get_register(regs, indx_offset);
    @@ -170,7 +170,7 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
    } else {
    addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
    if (addr_offset < 0)
    - goto out_err;
    + goto out;

    eff_addr = regs_get_register(regs, addr_offset);
    }
    @@ -180,9 +180,8 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)

    linear_addr = (unsigned long)eff_addr;

    +out:
    return (void __user *)linear_addr;
    -out_err:
    - return (void __user *)-1;
    }

    static int mpx_insn_decode(struct insn *insn,
    --
    Regards/Gruss,
    Boris.

    SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
    --

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