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SubjectRe: [PATCH v4 2/5] LoongArch: Use la.pcrel instead of la.abs for exception handlers
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On 02/16/2023 07:18 PM, Youling Tang wrote:
>
> On 02/16/2023 04:03 PM, Youling Tang wrote:
>>
>>
>> On 02/16/2023 03:10 PM, Xi Ruoyao wrote:
>>> On Thu, 2023-02-16 at 14:59 +0800, Jinyang He wrote:
>>>> +.macro la.abs reg, sym
>>>> +766:
>>>> + nop
>>>> + nop
>>>> + nop
>>>> + nop
>>>
>>> In the "formal" version we can code
>>>
>>> lu12i.w reg, 0
>>> ori reg, reg, 0
>>> lu32i.d reg, 0
>>> lu52i.d reg, reg, 0
>>>
>>> here. Then we only need to fixup the immediate slot so we can avoid
>>> using parse_r.
>>>
>>>
>>>> + .pushsection ".laabs", "aw", %progbits
>>>> +768:
>>>> + .word 768b-766b
>>>> + parse_r regno, \reg
>>>> + .word regno
>>>> + .dword \sym
>>>> + .popsection
>>>> +.endm
>>
>> I will try to modify a version for testing, using the following
>> definition, when the RELOCATABLE is turned on, the "la.abs macro" is
>> used, otherwise the "la.abs pseudo instruction" is still used as before.
>>
>> #ifdef CONFIG_RELOCATABLE
>> .macro la.abs reg, sym
>> lu12i.w reg, 0
>> ori reg, reg, 0
>> lu32i.d reg, 0
>> lu52i.d reg, reg, 0
>> .endm
>> #endif
>
> On the basis of the v4 patch set, remove patch2, and then add the
> following patches, and the test is successful on qemu.
>
> If this method is more acceptable to everyone, I will send v5.
>
> diff --git a/arch/loongarch/include/asm/asmmacro.h
> b/arch/loongarch/include/asm/asmmacro.h
> index 328bb956f241..adb04ae6b208 100644
> --- a/arch/loongarch/include/asm/asmmacro.h
> +++ b/arch/loongarch/include/asm/asmmacro.h
> @@ -667,4 +667,19 @@
> nor \dst, \src, zero
> .endm
>
> +#ifdef CONFIG_RELOCATABLE
> +.macro la.abs reg, sym
> +766:
> + lu12i.w \reg, 0
> + ori \reg, \reg, 0
> + lu32i.d \reg, 0
> + lu52i.d \reg, \reg, 0
> + .pushsection ".laabs", "aw", %progbits
> +768:
> + .dword 768b-766b
> + .dword \sym
> + .popsection
> +.endm
> +#endif
> +
> #endif /* _ASM_ASMMACRO_H */
> diff --git a/arch/loongarch/kernel/relocate.c
> b/arch/loongarch/kernel/relocate.c
> index 7d19cc0d2185..7ad327a554f9 100644
> --- a/arch/loongarch/kernel/relocate.c
> +++ b/arch/loongarch/kernel/relocate.c
> @@ -12,6 +12,7 @@
> #include <linux/start_kernel.h>
> #include <asm/bootinfo.h>
> #include <asm/early_ioremap.h>
> +#include <asm/inst.h>
> #include <asm/sections.h>
>
> #define RELOCATED(x) ((void *)((long)x + reloc_offset))
> @@ -45,6 +46,32 @@ static inline __init void relocate_relative(void)
> }
> }
>
> +static inline void __init relocate_laabs(long offset)
> +{
> + extern void *__laabs_begin;
> + extern void *__laabs_end;
> + struct laabs {
> + long offset;
> + long symvalue;
> + } *p;
> +
> + for (p = (void *)&__laabs_begin; (void *)p < (void
> *)&__laabs_end; p++) {
> + long v = p->symvalue + reloc_offset;
> + union loongarch_instruction *insn = (void *)p -
> p->offset + offset;
> + u32 lu12iw, ori, lu32id, lu52id;
> +
> + lu12iw = (v >> 12) & 0xfffff;
> + ori = v & 0xfff;
> + lu32id = (v >> 32) & 0xfffff;
> + lu52id = v >> 52;
> +
> + insn[0].reg1i20_format.immediate = lu12iw;
> + insn[1].reg2i12_format.immediate = ori;
> + insn[2].reg1i20_format.immediate = lu32id;
> + insn[3].reg2i12_format.immediate = lu52id;
> + }
> +}
> +
> #ifdef CONFIG_RANDOMIZE_BASE
> static inline __init unsigned long rotate_xor(unsigned long hash,
> const void *area, size_t
> size)
> @@ -168,8 +195,10 @@ void *__init do_kaslr(void)
> update_reloc_offset(&reloc_offset, offset);
> }
>
> - if (reloc_offset)
> + if (reloc_offset) {
> relocate_relative();
> + relocate_laabs(offset);
> + }

Self review:

if (reloc_offset)
relocate_relative();

relocate_laabs(offset);

>
> return kernel_entry;
> }
> @@ -181,6 +210,8 @@ void __init relocate_kernel(void)
>
> if (reloc_offset)
> relocate_relative();
> +
> + relocate_laabs(0);
> }
>
> /*
> diff --git a/arch/loongarch/kernel/vmlinux.lds.S
> b/arch/loongarch/kernel/vmlinux.lds.S
> index aec0b6567d24..0e58c68bf427 100644
> --- a/arch/loongarch/kernel/vmlinux.lds.S
> +++ b/arch/loongarch/kernel/vmlinux.lds.S
> @@ -66,6 +66,13 @@ SECTIONS
> __alt_instructions_end = .;
> }
>
> + . = ALIGN(8);
> + .laabs : AT(ADDR(.laabs) - LOAD_OFFSET) {
> + __laabs_begin = .;
> + *(.laabs)
> + __laabs_end = .;
> + }
> +
> .got : ALIGN(16) { *(.got) }
>
>
> Youling.
>

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