linux-kernel - Re: [question] insert ko failed because count_plts return 0 when CONFIG_RANDOMIZE

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Date:   Thu, 25 Mar 2021 06:21:59 +0000
From:   "chenjun (AM)" <chenjun102@...wei.com>
To:     Ard Biesheuvel <ardb@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        "Xiangrui (Euler)" <rui.xiang@...wei.com>,
        liuyanshi <liuyanshi@...wei.com>,
        wuzengkun <wuzengkun@...ilicon.com>
Subject: Re: [question] insert ko failed because count_plts return 0 when
 CONFIG_RANDOMIZE_BASE is not set

在 2021/3/24 16:29, Ard Biesheuvel 写道:
> On Wed, 24 Mar 2021 at 08:27, chenjun (AM) <chenjun102@...wei.com> wrote:
>>
>> Hi
>>
>> I make a Image for arm64 (without CONFIG_RANDOMIZE_BASE). And a ko (13M)
>> can not be inserted.
>>
> 
> How many large modules have you loaded already? The module region is
> only 128 MB, so if your modules are huge, you may run out of space.
> 
> Please check the kernel VA address and the load address of the module,
> and check whether they are more than 128 MB apart.
>

Thanks Ard

I will check it.

One more question, why is CONFIG_ARM64_MODULE_PLTS depended on 
CONFIG_RANDOMIZE_BASE?

> 
>> WARNING: CPU: 2 PID: 1998 at arch/arm64/kernel/module-plts.c:39
>> module_emit_plt_entry+0x100/0x118
>> ...
>> Call trace:
>> module_emit_plt_entry+0x100/0x118
>> apply_relocate_add+0x34c/0x570
>> ...
>>
>> I think the problem is that:
>> in apply_relocate_add:
>>                    case R_AARCH64_CALL26:
>>                        ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
>>                                                 AARCH64_INSN_IMM_26);
>>
>>                        if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
>>                            ovf == -ERANGE) {
>>                                val = module_emit_plt_entry(me, sechdrs,
>> loc, &rel[i], sym); realoc_insn_imm return -ERANGE (because the ko is
>> too big?)
>>
>> in module_emit_plt_entry:
>> WARN_ON(pltsec->plt_num_entries > pltsec->plt_max_entries)
>> pltsec->plt_max_entries is 0 if CONFIG_RANDOMIZE_BASE is not be set.
>>
>> a257e02 arm64/kernel: don't ban ADRP to work around Cortex-A53 erratum
>> #843419
>>     static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int
>> num,
>> -                              Elf64_Word dstidx)
>> +                              Elf64_Word dstidx, Elf_Shdr *dstsec)
>>     {
>> ...
>>                    switch (ELF64_R_TYPE(rela[i].r_info)) {
>>                    case R_AARCH64_JUMP26:
>>                    case R_AARCH64_CALL26:
>> +                       if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
>> +                               break;
>> +
>>
>> Why we need break if !IS_ENABLED(CONFIG_RANDOMIZE_BASE)? or any
>> restrictions on ko?
>>
>> I comment out this part of the code. the ko could be inserted, and seems
>> to work well. So is it a accepted way? or any solution for my case?
>>
>> --
>> Regards
>> Chen Jun
>>
> 


-- 
Regards
Chen Jun