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    Subject[PATCH 4.9 094/125] MIPS: Send SIGILL for linked branches in `__compute_return_epc_for_insn
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Maciej W. Rozycki <macro@imgtec.com>

    commit fef40be6da856afead4177aaa9d869a66fb3381f upstream.

    Fix commit 319824eabc3f ("MIPS: kernel: branch: Do not emulate the
    branch likelies on MIPS R6") and also send SIGILL rather than returning
    -SIGILL for BLTZAL, BLTZALL, BGEZAL and BGEZALL instruction encodings no
    longer supported in R6, except where emulated. Returning -SIGILL is
    never correct as the API defines this function's result upon error to be
    -EFAULT and a signal actually issued.

    Fixes: 319824eabc3f ("MIPS: kernel: branch: Do not emulate the branch likelies on MIPS R6")
    Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
    Cc: James Hogan <james.hogan@imgtec.com>
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/16398/
    Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/mips/kernel/branch.c | 12 ++++--------
    1 file changed, 4 insertions(+), 8 deletions(-)

    --- a/arch/mips/kernel/branch.c
    +++ b/arch/mips/kernel/branch.c
    @@ -473,10 +473,8 @@ int __compute_return_epc_for_insn(struct
    case bltzal_op:
    case bltzall_op:
    if (NO_R6EMU && (insn.i_format.rs ||
    - insn.i_format.rt == bltzall_op)) {
    - ret = -SIGILL;
    - break;
    - }
    + insn.i_format.rt == bltzall_op))
    + goto sigill_r2r6;
    regs->regs[31] = epc + 8;
    /*
    * OK we are here either because we hit a NAL
    @@ -507,10 +505,8 @@ int __compute_return_epc_for_insn(struct
    case bgezal_op:
    case bgezall_op:
    if (NO_R6EMU && (insn.i_format.rs ||
    - insn.i_format.rt == bgezall_op)) {
    - ret = -SIGILL;
    - break;
    - }
    + insn.i_format.rt == bgezall_op))
    + goto sigill_r2r6;
    regs->regs[31] = epc + 8;
    /*
    * OK we are here either because we hit a BAL

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