On 08/02/2017 08:00 PM, Atsushi Kumagai wrote:
> Hello,
>
>> On Mon, Jul 31, 2017 at 06:35:30AM -0700, Eric DeVolder wrote:
>>> When a page is excluded by any of the existing dump levels,
>>> that page may still be written to the ELF dump file, depending
>>> upon the PFN_EXCLUDED mechanism.
>>>
>>> The PFN_EXCLUDED mechanism looks for N consecutive "not
>>> dumpable" pages, and if found, the current ELF segment is
>>> closed out and a new ELF segment started, at the next dumpable
>>> page. Otherwise, if the PFN_EXCLUDED criteria is not meet (that
>>> is, there is a mix of dumpable and not dumpable pages, but not
>>> N consecutive not dumpable pages) all pages are written to the
>>> dump file.
>>>
>>> This patch implements a mechanism for those "not dumpable" pages
>>> that are written to the ELF dump file to fill those pages with
>>> constant data, rather than the original data. In other words,
>>> the dump file still contains the page, but its data is wiped.
>>>
>>> The motivation for doing this is to protect real user (customer)
>>> data from "leaking" through to a dump file when that data was
>>> intended to be omitted.
>>>
>>> Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
>>> ---
>>> makedumpfile.8 | 8 ++++++++
>>> makedumpfile.c | 32 +++++++++++++++++++++++++-------
>>> makedumpfile.h | 2 ++
>>> 3 files changed, 35 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/makedumpfile.8 b/makedumpfile.8
>>> index f94f2d7..64af0cf 100644
>>> --- a/makedumpfile.8
>>> +++ b/makedumpfile.8
>>> @@ -621,6 +621,14 @@ order from left to right. \fIVMCORE\fRs are assembled into a single
>>> # makedumpfile \-x vmlinux \-\-diskset=vmcore1 \-\-diskset=vmcore2 dumpfile
>>>
>>> .TP
>>> +\fB\-\-fill-excluded-pages FILL_VALUE\fR
>>
>> I am OK with --fill-excluded-pages to change default value but it is not needed
>> in my opinion. However, I think that we should have --no-fill-excluded-pages
>> variant. Just in case if somebody wish to disable default behavior
>
> Umm, I can't think of any cases where a user expects "not dumpable pages" to
> remain while he specifies a dump level to exclude those pages.
> That's why I suggested that this feature should be default.
I have changed the patch to do this behavior; I have eliminated the
option altogether. If I have misunderstood, please indicate as such.
>
> BTW, could you tell me the benefits of making FILL_VALUE changeable ?
The motivation for this was debugging; perhaps not very useful given
this is post-mortem debugging...
I've posted v2 of the patch.
Thanks,
eric
>
>>> +For the ELF dump file format, excluded pages may be written into the dump
>>> +file, but the page contents are wiped. This option allows the wipe value
>>> +to be changed from the default 0x5041474557495045UL "PAGEWIPE", or on
>>> +32-bit systems "WIPE".
>>
>> 0xDEAD9A6E == DEADPAGE where P == 9 (do you have better figure for P?) and G == 6
>>
>> This seems better for me because you do not need to convert it to ASCII
>> to see what it is. And fills exactly 32-bits.
>
> I'll leave it up to you :-)
>
> Thanks,
> Atsushi Kumagai
>
>>> +
>>> +
>>> +.TP
>>> \fB\-D\fR
>>> Print debugging message.
>>>
>>> diff --git a/makedumpfile.c b/makedumpfile.c
>>> index f85003a..cee0ab0 100644
>>> --- a/makedumpfile.c
>>> +++ b/makedumpfile.c
>>> @@ -7139,7 +7139,7 @@ out:
>>>
>>> int
>>> write_elf_load_segment(struct cache_data *cd_page, unsigned long long paddr,
>>> - off_t off_memory, long long size)
>>> + off_t off_memory, long long size, struct cycle *cycle)
>>> {
>>> long page_size = info->page_size;
>>> long long bufsz_write;
>>> @@ -7163,10 +7163,23 @@ write_elf_load_segment(struct cache_data *cd_page, unsigned long long paddr,
>>> else
>>> bufsz_write = size;
>>>
>>> - if (read(info->fd_memory, buf, bufsz_write) != bufsz_write) {
>>> - ERRMSG("Can't read the dump memory(%s). %s\n",
>>> - info->name_memory, strerror(errno));
>>> - return FALSE;
>>> + if (!is_dumpable(info->bitmap2, paddr_to_pfn(paddr), cycle)) {
>>> + unsigned k;
>>> + unsigned long *p = (unsigned long *)buf;
>>> + for (k = 0; k < info->page_size; k += sizeof(unsigned long)) {
>>> + *p++ = info->fill_excluded_pages_value;
>>> + }
>>> + if (lseek(info->fd_memory, bufsz_write, SEEK_CUR) < 0) {
>>> + ERRMSG("Can't seek the dump memory(%s). %s\n",
>>> + info->name_memory, strerror(errno));
>>> + return FALSE;
>>> + }
>>> + } else {
>>> + if (read(info->fd_memory, buf, bufsz_write) != bufsz_write) {
>>> + ERRMSG("Can't read the dump memory(%s). %s\n",
>>> + info->name_memory, strerror(errno));
>>> + return FALSE;
>>> + }
>>> }
>>> filter_data_buffer((unsigned char *)buf, paddr, bufsz_write);
>>> paddr += bufsz_write;
>>> @@ -7431,7 +7444,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
>>> */
>>> if (load.p_filesz)
>>> if (!write_elf_load_segment(cd_page, paddr,
>>> - off_memory, load.p_filesz))
>>> + off_memory, load.p_filesz, &cycle))
>>> return FALSE;
>>>
>>> load.p_paddr += load.p_memsz;
>>> @@ -7473,7 +7486,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
>>> */
>>> if (load.p_filesz)
>>> if (!write_elf_load_segment(cd_page, paddr,
>>> - off_memory, load.p_filesz))
>>> + off_memory, load.p_filesz, &cycle))
>>> return FALSE;
>>>
>>> off_seg_load += load.p_filesz;
>>> @@ -11057,6 +11070,7 @@ static struct option longopts[] = {
>>> {"splitblock-size", required_argument, NULL, OPT_SPLITBLOCK_SIZE},
>>> {"work-dir", required_argument, NULL, OPT_WORKING_DIR},
>>> {"num-threads", required_argument, NULL, OPT_NUM_THREADS},
>>> + {"fill-excluded-pages", required_argument, NULL, OPT_FILL_EXCLUDED_PAGES},
>>> {0, 0, 0, 0}
>>> };
>>>
>>> @@ -11083,6 +11097,7 @@ main(int argc, char *argv[])
>>> info->fd_dumpfile = -1;
>>> info->fd_bitmap = -1;
>>> info->kaslr_offset = 0;
>>> + info->fill_excluded_pages_value = 0x5041474557495045UL;
>>> initialize_tables();
>>>
>>> /*
>>> @@ -11218,6 +11233,9 @@ main(int argc, char *argv[])
>>> case OPT_NUM_THREADS:
>>> info->num_threads = MAX(atoi(optarg), 0);
>>> break;
>>> + case OPT_FILL_EXCLUDED_PAGES:
>>> + info->fill_excluded_pages_value = strtoul(optarg, NULL, 0);
>>> + break;
>>> case '?':
>>> MSG("Commandline parameter is invalid.\n");
>>> MSG("Try `makedumpfile --help' for more information.\n");
>>> diff --git a/makedumpfile.h b/makedumpfile.h
>>> index 8a05794..9ccd06d 100644
>>> --- a/makedumpfile.h
>>> +++ b/makedumpfile.h
>>> @@ -1266,6 +1266,7 @@ struct DumpInfo {
>>> int vmemmap_cnt;
>>> struct ppc64_vmemmap *vmemmap_list;
>>> unsigned long kaslr_offset;
>>> + unsigned long fill_excluded_pages_value; /* fill value for excluded pages */
>>>
>>> /*
>>> * page table info for ppc64
>>> @@ -2275,6 +2276,7 @@ struct elf_prstatus {
>>> #define OPT_WORKING_DIR OPT_START+15
>>> #define OPT_NUM_THREADS OPT_START+16
>>> #define OPT_PARTIAL_DMESG OPT_START+17
>>> +#define OPT_FILL_EXCLUDED_PAGES OPT_START+18
>>
>> Oh, no please fix alignment somehow here. Separate patch?
>> And I think that just in case it should be:
>>
>> #define OPT_FILL_EXCLUDED_PAGES (OPT_START+18)
>>
>> And probably this applies to others. Next patch?
>>
>> Daniel
>
>
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>
