On 10/24/2021 02:32 AM, Maciej W. Rozycki wrote:
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; +#elseWithout 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
You are right, I missed the point. I have refered to microMIPS64 Instruction Set. JRC and JRADDIUSP also can be used with $ra in microMIPS. I am not sure what compiler do at epilogue. But when we call $ra without saving $ra, it means return, I think. I will fix it later. Thanks, Jinyang.
