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SubjectRe: [PATCH 11/11] kexec: Support for Kexec on panic using new system call
On Fri, Feb 28, 2014 at 06:28:57PM +0100, Borislav Petkov wrote:

[..]
> > +/* Memory to backup during crash kdump */
> > +#define KEXEC_BACKUP_SRC_START (0UL)
> > +#define KEXEC_BACKUP_SRC_END (655360UL) /* 640K */
>
> I guess
>
> #define KEXEC_BACKUP_SRC_END (640 * 1024UL)
>
> should be more clear.

Will Change.

[..]
> > +/* Alignment required for elf header segment */
> > +#define ELF_CORE_HEADER_ALIGN 4096
> > +
> > +/* This primarily reprsents number of split ranges due to exclusion */
> > +#define CRASH_MAX_RANGES 16
> > +
> > +struct crash_mem_range {
> > + unsigned long long start, end;
>
> u64?

Ok, that's shorter. Can use that.

[..]
> > +
> > +/* Used while prepareing memory map entries for second kernel */
>
> s/prepareing/preparing/

Yep typo. Will fix.

[..]
> > +static int get_gart_ranges_callback(u64 start, u64 end, void *arg)
> > +{
> > + struct crash_elf_data *ced = arg;
> > +
> > + ced->gart_start = start;
> > + ced->gart_end = end;
> > +
> > + /* Not expecting more than 1 gart aperture */
> > + return 1;
> > +}
> > +
> > +
> > +/* Gather all the required information to prepare elf headers for ram regions */
> > +static int fill_up_ced(struct crash_elf_data *ced, struct kimage *image)
>
> All other functions have nice, spelled out names but not this one :)
>
> Why not fill_up_crash_elf_data()?

Will change it.

>
> > +{
> > + unsigned int nr_ranges = 0;
> > +
> > + ced->image = image;
> > +
> > + walk_system_ram_range(0, -1, &nr_ranges,
> > + get_nr_ram_ranges_callback);
> > +
> > + ced->max_nr_ranges = nr_ranges;
> > +
> > + /*
> > + * We don't create ELF headers for GART aperture as an attempt
> > + * to dump this memory in second kernel leads to hang/crash.
> > + * If gart aperture is present, one needs to exclude that region
> > + * and that could lead to need of extra phdr.
> > + */
> > +
>
> superfluous newline.

Will remove.

[..]
> > +int load_crashdump_segments(struct kimage *image)
> > +{
> > + unsigned long src_start, src_sz;
> > + unsigned long elf_addr, elf_sz;
> > + int ret;
> > +
> > + /*
> > + * Determine and load a segment for backup area. First 640K RAM
> > + * region is backup source
> > + */
> > +
> > + ret = walk_system_ram_res(KEXEC_BACKUP_SRC_START, KEXEC_BACKUP_SRC_END,
> > + image, determine_backup_region);
> > +
> > + /* Zero or postive return values are ok */
> > + if (ret < 0)
> > + return ret;
> > +
> > + src_start = image->arch.backup_src_start;
> > + src_sz = image->arch.backup_src_sz;
> > +
> > + /* Add backup segment. */
> > + if (src_sz) {
> > + ret = kexec_add_buffer(image, __va(src_start), src_sz, src_sz,
> > + PAGE_SIZE, 0, -1, 0,
> > + &image->arch.backup_load_addr);
> > + if (ret)
> > + return ret;
> > + }
> > +
> > + /* Prepare elf headers and add a segment */
> > + ret = prepare_elf_headers(image, &elf_addr, &elf_sz);
> > + if (ret)
> > + return ret;
> > +
> > + image->arch.elf_headers = elf_addr;
> > + image->arch.elf_headers_sz = elf_sz;
> > +
> > + ret = kexec_add_buffer(image, (char *)elf_addr, elf_sz, elf_sz,
>
> For some reason, my compiler complains here:
>
> arch/x86/kernel/crash.c: In function ‘load_crashdump_segments’:
> arch/x86/kernel/crash.c:704:6: warning: ‘elf_sz’ may be used uninitialized in this function [-Wuninitialized]
> arch/x86/kernel/crash.c:704:24: warning: ‘elf_addr’ may be used uninitialized in this function [-Wuninitialized]
>
> It is likely bogus, though.

Hmm..., I did not see these warnings with my setup. elf_addr and elf_sz
will be initialized by prepare_elf_headers(). Not sure why compiler is
complaining.

[..]
> > + pr_debug("Final command line is:%s\n", cmdline_ptr);
>
> one space after ":"

Ok. will do.

>
> The rest looks ok to me, but that doesn't mean a whole lot considering
> my very limited kexec knowledge.

Thanks for review. We need many eyes on this patch set. I will make
changes and post another version for review.

Thanks
Vivek
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