[PATCH v2] riscv: optimize ELF relocation function in riscv

[Conor Dooley]

Hey Amma,

On Fri, May 12, 2023 at 04:51:53PM +0800, Amma Lee wrote:
> The patch can optimize the running times of "insmod" command by modify ELF
> relocation function.
> When install the riscv ELF driver which contains multiple
> symbol table items to be relocated, kernel takes a lot of time to
> execute the relocation. For example, we install a 3+MB driver need 180+s.
> We focus on the riscv kernel handle R_RISCV_HI20 and R_RISCV_LO12 type
> items relocation function and find that there are two for-loops in this
> function. If we modify the begin number in the second for-loops iteration,
> we could save significant time for installation. We install the 3+MB
> driver could just need 2s.
> 
> Signed-off-by: Amma Lee <lixiaoyun at binary-semi.com>

> Reviewed-by: Conor Dooley <conor at kernel.org>

I did not provide this tag. Do not add tags that you were not explicitly
given by people.

Also, you didn't actually even implement all of the things I pointed out
either :(

> 
> ---
>  arch/riscv/kernel/module.c | 53 ++++++++++++++++++++++++++++++----------------
>  1 file changed, 35 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index 55507b0..1683c1d 100755
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -385,9 +385,17 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  
>  		if (type == R_RISCV_PCREL_LO12_I || type == R_RISCV_PCREL_LO12_S) {
>  			unsigned int j;
> -			/*Modify the j for-loops begin number from last iterates end value*/
> +
> +			/*
> +			* In the second for-loops, each traversal for j is
                        ^^
Comment in passing here, we align the *s in comments.

> +			* starts from 0 to the symbol table item index which
> +			* is detected. By the tool "readelf", we find that all
> +			* the symbol table items about R_RISCV_PCREL_HI20 type
> +			* are incrementally added in order. It means that we
> +			* could interate the j with the previous loop end
> +			* value(j_idx) as the begin number in the next loop;
> +			*/
>  			for (j = j_idx; j < sechdrs[relsec].sh_size / sizeof(*rel); j++) {
> -			/* Modify end */
>  				unsigned long hi20_loc =
>  					sechdrs[sechdrs[relsec].sh_info].sh_addr
>  					+ rel[j].r_offset;
> @@ -420,22 +428,30 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  					break;
>  				}
>  			}
> +
>  			if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
> -				if(j_idx == 0){
> +				if (j_idx == 0) {
>  					pr_err(
>  						"%s: Can not find HI20 relocation information\n",
>  						me->name);
>  					return -EINVAL;
>  				}
> -				
> -				

^^ and this is one of the checkpatch complaints I mentioned last time,
no double blank lines please.

Also, this version of the patch doesn't actually apply for me to
v6.4-rc1 anymore, but the file has not been modified in upstream since
29/01. Not too sure what you have used as the base for this as a result
:/

Thanks,
Conor.
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