On Wed, Feb 26, 2014 at 11:32:56AM -0500, Vivek Goyal wrote: > We have been using sha256 for last 7-8 years in kexec-tools and nobody > asked for changing hash algorithm so far. > > So yes, somebody wanting to use a different algorithm is a possibility > but I don't think it is likely in near future. > > This patchset is already very big. I would rather make it work with > sha256 and down the line one can make it more generic if they feel > the need. This is not a user space API/ABI and one should be able to > change it without breaking any user space applications. > > So I really don't feel the need of making it more complicated, pull in > all the crypto API in purgaotry to support other kind of hash algorithms > in purgatory. Ok, makes sense. Right, if someone needs it, someone could add that support fairly easily. > No. One can modify purgatory object symbol entry64_regs dynamically from > outside and purpose of this code is to load values into registers. At > compile time value of entry64_regs is 0 so it kind of gives the impression > that we are just trying to zero registers. > > At kernel load time, we set values of some of those registers. Stack and > kernel entry point is one of those. Look at > arch/x86/kernel/kexec-bzimage.c > > regs64.rbx = 0; /* Bootstrap Processor */ > regs64.rsi = bootparam_load_addr; > regs64.rip = kernel_load_addr + 0x200; > regs64.rsp = (unsigned long)stack; > ret = kexec_purgatory_get_set_symbol(image, "entry64_regs", ®s64, > sizeof(regs64), 0); Ok, thanks for explaining. > Kdump kernel runs from reserved region of memory. But we also found on > x86, that it still needed first 640KB of memory to boot. So before jumping > to second kernel, we copy first 640KB in reserved region and let second > kernel use first 640KB. We call this concept as backup region as we are > backing up an area of memory so that second kernel does not overwrite it. > > For more details on backup region have a look at this paper. > > http://lse.sourceforge.net/kdump/documentation/ols2oo5-kdump-paper.pdf That's valuable info, can we put some of it in a comment in the code somewhere? > Yep. Right now these patches support 64bit kernel only and I put some > code for 32bit so that there are no compilation failures. > > Though 32bit is becoming less relevant with every passing day, still > supporting it on 32bit is a good idea. It can happen down the line tough. Ok. Thanks. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --
