Messages in this thread | | | Date | Tue, 2 May 2006 10:56:09 +0900 | From | "Magnus Damm" <> | Subject | Re: [Fastboot] [PATCH] kexec: Avoid overwriting the current pgd (i386) |
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On 5/2/06, Eric W. Biederman <ebiederm@xmission.com> wrote: > Vivek Goyal <vgoyal@in.ibm.com> writes: > > On Mon, May 01, 2006 at 06:49:16PM +0900, Magnus Damm wrote: > >> --- 0001/include/linux/kexec.h > >> +++ work/include/linux/kexec.h 2006-05-01 11:13:14.000000000 +0900 > >> @@ -69,6 +69,17 @@ struct kimage { > >> unsigned long start; > >> struct page *control_code_page; > >> > >> + /* page_table_a[] holds enough pages to create a new page table > >> + * that maps the control page twice.. > >> + */ > >> + > >> +#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE) > >> + struct page *page_table_a[3]; /* (2 * pte) + pgd */ > >> +#endif > >> +#if defined(CONFIG_X86_32) && defined(CONFIG_X86_PAE) > >> + struct page *page_table_a[5]; /* (2 * pte) + (2 * pmd) + pgd */ > >> +#endif > >> + > > > > Would it make a cleaner interface if these array of pointers are maintained > > in arch dependent code as global variables instead of putting in arch > > independent code. Existing code does something simlar. This becomes further > > ugly when another array comes into the picture for x86_64 in next patch. > > (page_table_b) > > Well global variables don't quite work in the normal case. > > However it probably makes most sense to maintain the needed variables > in a structure on the control page. Which will keep them out of harms way, > and won't require patches to the generic code.
I agree with both of you that the #ifdefs in struct kimage should be avoided, but I wonder if adding variables in a structure on the control page is the easiest and cleanest way.
I think that defining a structure for each architecture in include/asm/kexec.h that is included in struct kimage is the best way to go. Then each architecture can have whatever data it wants there, and we both avoid #ifdefs in struct kimage _and_ we stay away from overly complicated code that just allocates, frees and parses architecture-dependent data.
Thanks for the input,
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