Re: [PATCH v3 2/2] x86: Parse CONFIG_CMDLINE in compressed kernel

[Borislav Petkov]

On Thu, May 05, 2022 at 01:32:24PM +0300, Baskov Evgeniy wrote:

Same note on the subject format as for your previous patch.

> CONFIG_CMDLINE, CONFIG_CMDLINE_BOOL, and CONFIG_CMDLINE_OVERRIDE were
> ignored during options lookup in compressed kernel.
> 
> Parse CONFIG_CMDLINE-related options correctly in compressed kernel
> code.
> 
> cmd_line_ptr_init is explicitly placed in .data section since it is
> used and expected to be equal to zero before .bss section is cleared.

What I'm missing in this commit message is the use case which you have
in your 0/2 mail.

Also, to the tone of your commit messages, from
Documentation/process/submitting-patches.rst:

 "Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
  instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
  to do frotz", as if you are giving orders to the codebase to change
  its behaviour."

Also, do not talk about what your patch does - that should hopefully be
visible in the diff itself. Rather, talk about *why* you're doing what
you're doing.

> Signed-off-by: Baskov Evgeniy <baskov@xxxxxxxxx>
> 
> diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c
> index f1add5d85da9..261f53ad395a 100644
> --- a/arch/x86/boot/compressed/cmdline.c
> +++ b/arch/x86/boot/compressed/cmdline.c
> @@ -1,6 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include "misc.h"
>  
> +#define COMMAND_LINE_SIZE 2048
> +
>  static unsigned long fs;
>  static inline void set_fs(unsigned long seg)
>  {
> @@ -12,12 +14,32 @@ static inline char rdfs8(addr_t addr)
>  	return *((char *)(fs + addr));
>  }
>  #include "../cmdline.c"
> +
> +#ifdef CONFIG_CMDLINE_BOOL
> +static char builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
> +static bool builtin_cmdline_init __section(".data");
> +#endif
> +
>  unsigned long get_cmd_line_ptr(void)
>  {
>  	unsigned long cmd_line_ptr = boot_params->hdr.cmd_line_ptr;
> -
>  	cmd_line_ptr |= (u64)boot_params->ext_cmd_line_ptr << 32;
>  
> +#ifdef CONFIG_CMDLINE_BOOL
> +	if (!builtin_cmdline_init) {
> +		if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
> +			strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
> +			strlcat(builtin_cmdline,
> +				(char *)cmd_line_ptr,
> +				COMMAND_LINE_SIZE);
> +		}
> +
> +		builtin_cmdline_init = 1;
> +	}
> +
> +	cmd_line_ptr = (unsigned long)builtin_cmdline;
> +#endif

I had asked this already but let me try again: instead of copying this
from kernel proper, why don't you add a common helper which you call
from both locations?

And it is not like this is going to be a huge function so you can stick
it into a shared header in arch/x86/include/asm/shared/ and it'll get
inlined into both locations...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette