linux-kernel - Re: [PATCH] binfmt_elf_fdpic: clean up debug warnings

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Message-ID: <202309270858.680FCD9A85@keescook>
Date:   Wed, 27 Sep 2023 08:59:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Ungerer <gerg@...nel.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, palmer@...osinc.com,
        ebiederm@...ssion.com, brauner@...nel.org, viro@...iv.linux.org.uk
Subject: Re: [PATCH] binfmt_elf_fdpic: clean up debug warnings

On Wed, Sep 27, 2023 at 11:29:33PM +1000, Greg Ungerer wrote:
> The binfmt_elf_fdpic loader has some debug trace that can be enabled at
> build time. The recent 64-bit additions cause some warnings if that
> debug is enabled, such as:
> 
>     fs/binfmt_elf_fdpic.c: In function ‘elf_fdpic_map_file’:
>     fs/binfmt_elf_fdpic.c:46:33: warning: format ‘%x’ expects argument of type ‘unsigned int’, but argument 3 has type ‘Elf64_Addr’ {aka ‘long long unsigned int’} [-Wformat=]
>        46 | #define kdebug(fmt, ...) printk("FDPIC "fmt"\n" ,##__VA_ARGS__ )
>           |                                 ^~~~~~~~
>     ./include/linux/printk.h:427:25: note: in definition of macro ‘printk_index_wrap’
>       427 |                 _p_func(_fmt, ##__VA_ARGS__);                           \
>           |                         ^~~~
> 
> Cast values to the largest possible type (which is equivilent to unsigned
> long long in this case) and use appropriate format specifiers to match.

It seems like these should all just be "unsigned long", yes?

-Kees

> 
> Fixes: b922bf04d2c1 ("binfmt_elf_fdpic: support 64-bit systems")
> Signed-off-by: Greg Ungerer <gerg@...nel.org>
> ---
>  fs/binfmt_elf_fdpic.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 43b2a2851ba3..97c3e8551aac 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -900,10 +900,12 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
>  	kdebug("- DYNAMIC[]: %lx", params->dynamic_addr);
>  	seg = loadmap->segs;
>  	for (loop = 0; loop < loadmap->nsegs; loop++, seg++)
> -		kdebug("- LOAD[%d] : %08x-%08x [va=%x ms=%x]",
> +		kdebug("- LOAD[%d] : %08llx-%08llx [va=%llx ms=%llx]",
>  		       loop,
> -		       seg->addr, seg->addr + seg->p_memsz - 1,
> -		       seg->p_vaddr, seg->p_memsz);
> +		       (unsigned long long) seg->addr,
> +		       (unsigned long long) seg->addr + seg->p_memsz - 1,
> +		       (unsigned long long) seg->p_vaddr,
> +		       (unsigned long long) seg->p_memsz);
>  
>  	return 0;
>  
> @@ -1082,9 +1084,10 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
>  		maddr = vm_mmap(file, maddr, phdr->p_memsz + disp, prot, flags,
>  				phdr->p_offset - disp);
>  
> -		kdebug("mmap[%d] <file> sz=%lx pr=%x fl=%x of=%lx --> %08lx",
> -		       loop, phdr->p_memsz + disp, prot, flags,
> -		       phdr->p_offset - disp, maddr);
> +		kdebug("mmap[%d] <file> sz=%llx pr=%x fl=%x of=%llx --> %08lx",
> +		       loop, (unsigned long long) phdr->p_memsz + disp,
> +		       prot, flags, (unsigned long long) phdr->p_offset - disp,
> +		       maddr);
>  
>  		if (IS_ERR_VALUE(maddr))
>  			return (int) maddr;
> @@ -1146,8 +1149,9 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
>  
>  #else
>  		if (excess > 0) {
> -			kdebug("clear[%d] ad=%lx sz=%lx",
> -			       loop, maddr + phdr->p_filesz, excess);
> +			kdebug("clear[%d] ad=%llx sz=%lx", loop,
> +			       (unsigned long long) maddr + phdr->p_filesz,
> +			       excess);
>  			if (clear_user((void *) maddr + phdr->p_filesz, excess))
>  				return -EFAULT;
>  		}
> -- 
> 2.25.1
> 

-- 
Kees Cook