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    Subject[PATCH v2 4/4] MIPS: Add is_jr_ra_ins() to end the loop early
    Date
    For those leaf functions, they are likely to have no stack operations.
    Add is_jr_ra_ins() to determine whether jr ra has been touched before
    the frame_size is found. Without this patch, the get frame_size operation
    may be out of range and get the frame_size from the next nested function.

    There is no POOL32A format in uapi/asm/inst.h, so some bits here use the
    format of r_format instead.
    e.g.
    ---------------------------------------------------------------------
    | format | 31:26 | 25:21 | 20:16 | 15:6 | 5:0 |
    -----------------+---------+-------+-------+------------+------------
    | pool32a_format | pool32a | rt | rs | jalrc | pool32axf |
    -----------------+---------+-------+-------+------------+------------
    | r_format | opcode | rs | rt | rd:5, re:5 | func |
    ---------------------------------------------------------------------

    Signed-off-by: Jinyang He <hejinyang@loongson.cn>
    ---
    v2:
    - microMIPS: ip->r_format.rs -> ip->r_format.rt

    arch/mips/kernel/process.c | 34 +++++++++++++++++++++++++++++++++-
    1 file changed, 33 insertions(+), 1 deletion(-)

    diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
    index adf29f7..592f02e 100644
    --- a/arch/mips/kernel/process.c
    +++ b/arch/mips/kernel/process.c
    @@ -186,6 +186,36 @@ struct mips_frame_info {
    #define J_TARGET(pc,target) \
    (((unsigned long)(pc) & 0xf0000000) | ((target) << 2))

    +static inline int is_jr_ra_ins(union mips_instruction *ip)
    +{
    +#ifdef CONFIG_CPU_MICROMIPS
    + /*
    + * jr16 ra
    + * jr ra
    + */
    + if (mm_insn_16bit(ip->word >> 16)) {
    + if (ip->mm16_r5_format.opcode == mm_pool16c_op &&
    + ip->mm16_r5_format.rt == mm_jr16_op &&
    + ip->mm16_r5_format.imm == 31)
    + return 1;
    + return 0;
    + }
    +
    + if (ip->r_format.opcode == mm_pool32a_op &&
    + ip->r_format.func == mm_pool32axf_op &&
    + ((ip->u_format.uimmediate >> 6) & GENMASK(9, 0)) == mm_jalr_op &&
    + ip->r_format.rt == 31)
    + return 1;
    + return 0;
    +#else
    + if (ip->r_format.opcode == spec_op &&
    + ip->r_format.func == jr_op &&
    + ip->r_format.rs == 31)
    + return 1;
    + return 0;
    +#endif
    +}
    +
    static inline int is_ra_save_ins(union mips_instruction *ip, int *poff)
    {
    #ifdef CONFIG_CPU_MICROMIPS
    @@ -398,7 +428,9 @@ static int get_frame_info(struct mips_frame_info *info)
    last_insn_size = 4;
    }

    - if (!info->frame_size) {
    + if (is_jr_ra_ins(ip)) {
    + break;
    + } else if (!info->frame_size) {
    is_sp_move_ins(&insn, &info->frame_size);
    continue;
    } else if (!saw_jump && is_jump_ins(ip)) {
    --
    2.1.0
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