sg_set_page not usable for .bss?

From: Jan Engelhardt
Date: Mon Dec 01 2008 - 17:40:32 EST

On Monday 2008-12-01 23:02, John Haxby wrote:
>>>+ sg_init_table(sg, 2);
>>>+ sg_set_buf(&sg[0], data, n);
>>>+ strcpy(digest_password, sysrq_password);
>>>+ i = strlen(digest_password);
>>>+ sg_set_buf(&sg[1], digest_password, i);
>> Could we directly use sysrq_password instead of copying it to
>> digest_password first?
> No :-) Eventually I discovered the reason my code wasn't working
> boils down to the definition of sg_set_buf:
> sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf))
> which doesn't work for sysrq_password. I don't know why I'll
> double check.

Well, sysrq_password is in the .bss section, where as digest_password
is on the heap due to being kmalloc'ed. Maybe that makes a difference?
Someone more versed with the virtual memory layer might know.

>+static char sysrq_password[64];
>+ digest_password = kmalloc(sizeof(sysrq_password), GFP_KERNEL);
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