> -----Original Message----- > From: Magnus Damm [mailto:[EMAIL PROTECTED] > Sent: 2006年11月22日 12:53 > To: [EMAIL PROTECTED] > Cc: Magnus Damm; fastboot@lists.osdl.org; Horms; [EMAIL PROTECTED]; Zou, > Nanhai > Subject: Re: [PATCH 005/013] kexec-tools: Make use of > crash_create_elf64_headers() (x86_64) > > Hi Vivek and Nan hai, > > On 11/22/06, Vivek Goyal <[EMAIL PROTECTED]> wrote: > > On Tue, Nov 21, 2006 at 02:56:23PM +0900, Magnus Damm wrote: > > [..] > > > >> > > > >> +static struct crash_elf_info elf_info = > > > >> +{ > > > >> + class: ELFCLASS64, > > > >> + data: ELFDATA2LSB, > > > >> + machine: EM_X86_64, > > > >> + alignment: 1024, > > > > > > > >This alignment thing is confusing me. Can you give some more details > > > >please? > > > > > > Well, I only put it in because the original code had some alignment code: > > > > > > @@ -734,7 +615,6 @@ int load_crashdump_segments(struct kexec > > > void *tmp; > > > unsigned long sz, elfcorehdr; > > > int nr_ranges, align = 1024, i; > > > - long int nr_cpus = 0; > > > struct memory_range *mem_range, *memmap_p; > > > > > > if (get_kernel_paddr(info)) > > > @@ -764,20 +644,9 @@ int load_crashdump_segments(struct kexec > > > return -1; > > > > > > /* Create elf header segment and store crash image data. */ > > > - nr_cpus = sysconf(_SC_NPROCESSORS_CONF); > > > - if (nr_cpus < 0) { > > > - fprintf(stderr,"kexec_load (elf header segment)" > > > - " failed: %s\n", strerror(errno)); > > > - return -1; > > > - } > > > - sz = sizeof(Elf64_Ehdr) + nr_cpus * sizeof(Elf64_Phdr) + > > > - nr_ranges * sizeof(Elf64_Phdr); > > > - sz = (sz + align - 1) & ~(align -1); > > > - tmp = xmalloc(sz); > > > - memset(tmp, 0, sz); > > > - > > > - /* Prepare ELF64 core heaers. */ > > > - if (prepare_crash_memory_elf64_headers(info, tmp, sz) < 0) > > > + if (crash_create_elf64_headers(info, &elf_info, > > > + crash_memory_range, nr_ranges, > > > + &tmp, &sz) < 0) > > > return -1; > > > > > > Have a look at the align variable above? It is set to 1024. So I just > > > broke out the alignment number and put it into the elf_info structure > > > to make it per-arch. > > > > > > I don't know why the number of bytes allocated are rounded to an even > > > 1024. It is probably because the data that follows the headers should > > > be aligned. Word-size aligment I understand, but 1024 I don't. 1024 > > > was probably a handy value that happened to work regardless of 32 or > > > 64 bit elf format... > > > > > > > > > Ok. Now I remember. I had put this alignment to make sure elf header > > segment is atleast 1K aligned. And the reason behind that is when we > > prepare the memmap= options to pass to second kernel, we can pass the > > memory only with a granularity of KB and not less than that. > > > > So I need to remove the elf core header segment from the list of memory > > regions which second kernel can use. I used delete_memmap() function to > > do that and create a new list. If segments/memory regions I am handling > > are at least 1K aligned, it becomes easier to handle them. Otherwise > > its chaos. > > That explains the alignment. Thank you! Always aligning to 1K makes sense > then. > > Nan hai, you align to EFI_PAGE_SIZE instead of 1K on ia64. Do you have > any special reason for doing so? > > Right now I assume it is a "copy-and-paste-o" so my patches use > 1K-alignment instead. > ELF spec says, loadable process segments should be aligned to page size. But for core dump data, I guess 1k might be ok. But why not align them to page size? Thanks Zou Nan hai
> > So I guess, its fine to continue with this alignment thing. Though > > a small comment might help to future code writers. > > I see this as an improvement or clarification for the existing code. > So I'll cook up a separate patch with the comment next week when I'm > back from a few days vacation. > > Thanks! > > / magnus
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