On 07/10/2014, Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> wrote:
> Even though I just sent a new patch...
>
> On 10/06/2014 11:23 PM, David Miller wrote:
>> From: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
>> Date: Mon, 06 Oct 2014 11:06:27 -0500
>>
>>> sparc64 defines COMMAND_LINE_SIZE to be 2048, but the boot string is
>>> hard-coded to be 256 bytes long.
>>>
>>> based on a patch by Bob Picco
>>>
>>> Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
>>
>> I think we might be limited by the size of barg_out[] in the SILO
>> bootloader, which is 1024 bytes.
>>
>> SILO massages the command line into barg_out[] then does:
>>
>> if (architecture == sun4u)
>> kernel_params = (char *)((hdrs->bootstr_info_ptr_low - 0x400000) +
>> (image_base - 0x4000));
>> ...
>> if (kernel_params) {
>> extern char barg_out[];
>> int len = *(unsigned int *)kernel_params;
>>
>> strncpy (kernel_params + 8, barg_out, len);
>> kernel_params [8 + len - 1] = 0;
>> *(unsigned int *)(kernel_params + 4) = 1;
>> }
>>
>> So it blindly copies however many bytes you tell it to in that
>> bootstr_info area :-/
>
> strncpy will still stop at the first null character, so the only way it
> will copy more than 1024 bytes would be if it has already overflowed
> barg_out in constructing the command line. Writing the final null
> terminator into kernel_params is not a problem.
>
Just a note from the strncpy manpage:
"If the length of src is less than n, strncpy() writes additional null
bytes to dest to ensure that a total of n bytes are written."
So strncpy always writes len bytes, regardless of the presence of a null char.
(Unless silo strncpy is different ?)
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