Re: [Xen-devel] [PATCH 2/7] x86/alt: Clean up struct alt_instr and its users

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Feb 12, 2018 at 11:23:02AM +0000, Andrew Cooper wrote:
>  * Rename some fields for consistency and clarity, and use standard types.
>  * Don't opencode the use of ALT_{ORIG,REPL}_PTR().

And change u8 etc.

> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/arch/x86/alternative.c        | 24 ++++++++++++------------
>  xen/include/asm-x86/alternative.h | 12 ++++++------
>  2 files changed, 18 insertions(+), 18 deletions(-)
> 
> diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
> index 5c8b6f6..f8ddab5 100644
> --- a/xen/arch/x86/alternative.c
> +++ b/xen/arch/x86/alternative.c
> @@ -163,8 +163,6 @@ void init_or_livepatch apply_alternatives(const struct 
> alt_instr *start,
>                                            const struct alt_instr *end)
>  {
>      const struct alt_instr *a;
> -    u8 *instr, *replacement;
> -    u8 insnbuf[MAX_PATCH_LEN];
>  
>      printk(KERN_INFO "alt table %p -> %p\n", start, end);
>  
> @@ -179,23 +177,25 @@ void init_or_livepatch apply_alternatives(const struct 
> alt_instr *start,
>       */
>      for ( a = start; a < end; a++ )
>      {
> -        instr = (u8 *)&a->instr_offset + a->instr_offset;
> -        replacement = (u8 *)&a->repl_offset + a->repl_offset;
> -        BUG_ON(a->replacementlen > a->instrlen);
> -        BUG_ON(a->instrlen > sizeof(insnbuf));
> +        uint8_t *orig = ALT_ORIG_PTR(a);
> +        uint8_t *repl = ALT_REPL_PTR(a);
> +        uint8_t buf[MAX_PATCH_LEN];
> +
> +        BUG_ON(a->repl_len > a->orig_len);
> +        BUG_ON(a->orig_len > sizeof(buf));
>          BUG_ON(a->cpuid >= NCAPINTS * 32);
> +
>          if ( !boot_cpu_has(a->cpuid) )
>              continue;
>  
> -        memcpy(insnbuf, replacement, a->replacementlen);
> +        memcpy(buf, repl, a->repl_len);
>  
>          /* 0xe8/0xe9 are relative branches; fix the offset. */
> -        if ( a->replacementlen >= 5 && (*insnbuf & 0xfe) == 0xe8 )
> -            *(s32 *)(insnbuf + 1) += replacement - instr;
> +        if ( a->repl_len >= 5 && (*buf & 0xfe) == 0xe8 )
> +            *(s32 *)(buf + 1) += repl - orig;

Mind changing s32 to int32_t?

In any case:

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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