lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 25 Oct 2021 10:11:35 +0800 From: Jinyang He <hejinyang@...ngson.cn> To: "Maciej W. Rozycki" <macro@...am.me.uk> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, Paul Burton <paulburton@...nel.org>, Jun-Ru Chang <jrjang@...ltek.com> Subject: Re: [PATCH 4/4] MIPS: Add is_jr_ra_ins() to end the loop early 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@...ngson.cn> >> --- >> 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 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.
Powered by blists - more mailing lists