Re: git: 41ee91c64f47 - main - newfs_msdos: fix build on non-FreeBSD systems

> On Jun 4, 2024, at 8:21 AM, Shawn Webb <shawn.webb@hardenedbsd.org> wrote:
> 
> On Tue, Jun 04, 2024 at 06:28:19AM +0000, Stefan Eßer wrote:
>> The branch main has been updated by se:
>> 
>> URL: https://cgit.FreeBSD.org/src/commit/?id=41ee91c64f47faaa8131df3cd8a63bdb60fa486a
>> 
>> commit 41ee91c64f47faaa8131df3cd8a63bdb60fa486a
>> Author:     Stefan Eßer <se@FreeBSD.org>
>> AuthorDate: 2024-06-04 06:26:09 +0000
>> Commit:     Stefan Eßer <se@FreeBSD.org>
>> CommitDate: 2024-06-04 06:26:09 +0000
>> 
>>    newfs_msdos: fix build on non-FreeBSD systems
>> 
>>    Disable data area alignment if the build environment does not define
>>    PAGE_SIZE (e.g., when building on Linux or macOS).
>> 
>>    Reported by:    jrtc27
>>    MFC after:      1 week
>> ---
>> sbin/newfs_msdos/mkfs_msdos.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>> 
>> diff --git a/sbin/newfs_msdos/mkfs_msdos.c b/sbin/newfs_msdos/mkfs_msdos.c
>> index 423fbbcadcc5..1bca560a59e1 100644
>> --- a/sbin/newfs_msdos/mkfs_msdos.c
>> +++ b/sbin/newfs_msdos/mkfs_msdos.c
>> @@ -571,7 +571,11 @@ mkfs_msdos(const char *fname, const char *dtype, const struct msdos_options *op)
>> 	    if (o.align)
>> 		alignto = bpb.bpbSecPerClust;
>> 	    else
>> +#ifdef	PAGE_SIZE
>> 		alignto = PAGE_SIZE / bpb.bpbBytesPerSec;
>> +#else
>> +	        alignto = 1;
>> +#endif
> 
> Imagine the following:
> 
> 1. someone builds FreeBSD on Linux or macOS
> 2. that build is deployed
> 3. FreeBSD is rebuilt on that deployment
> 
> Could the value of alignto be different on step 1 versus step 3?

Hi Shawn,
	Assuming the tool is built for the host, yes it would run into the issues you’re describing. If it’s targeting FreeBSD though or an OS that allows direct access to PAGE_SIZE, e.g., NetBSD, it will use whatever the OS defines for PAGE_SIZE in the appropriate headers.
Cheers,
-Enji