On Tue, 12 Jan 2021, Jinyang He wrote:
> 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.
>
> Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
> ---
> 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 bef8f8d..9e6f194 100644
> --- a/arch/mips/kernel/process.c
> +++ b/arch/mips/kernel/process.c
> @@ -205,6 +205,36 @@ 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.rs == 31)
> + return 1;
> + return 0;
> +#else
Without looking into it much, this is likely missing the point, because
while technically inteed JR and JR16 can be used with $ra in microMIPS
machine code (there's JRS too), in reality either JRC or JRADDIUSP will.
[Wading through e-mail recovered from mid-Jan linux-mips.org crash.]
Maciej
