Re: [PATCH Makedumpfile 0/4] x86_64: Fix page_offset for randomized base enabled

[Dave Young <dyoung@redhat.com>]

Hi Pratyush,

On 10/24/16 at 10:18pm, Pratyush Anand wrote:
> Patch 1/4 fixes page_offset calculation, so that it is correctly calculated
> on KASLR enabled kernel as well.
> Patch 2/4 simplifies VA to PA translation. New code has been benchmarked
> against old code on a 4T system.
> Patch 3/4 and 4/4 is removal of (now) unnecessary code.
> 
> I think, we should find a way to kill find_vememmap() as well, so that
> VMEMMAP_START can be removed. I have very limited idea about x86, so unable
> to do that as of now.
> 
> Pratyush Anand (4):
>   x86_64: Calculate page_offset from pt_load
>   x86_64: translate all VA to PA using page table values
>   x86_64: kill is_vmalloc_addr_x86_64()
>   x86_64: kill some unused initialization
> 
>  arch/x86_64.c  | 84 ++++++++++++++++++++--------------------------------------
>  makedumpfile.h |  9 +++----
>  2 files changed, 32 insertions(+), 61 deletions(-)
> 

According to our test, with these patches the dumped vmcore is correct
which means simple crash test `bt` works. But the saved vmcore size is
larger than before.

I collected two --message-level 31 logs with/without your patches, the
kernel kaslr was disabled during my test so that we can focus on the
vmcore size issue, it looks like mem_map address was not collected
correctly.

[please ignore the patched log extra debug message I added] 

--- unpatched-makedumpfile.txt	2016-10-27 10:31:34.152962407 +0800
+++ patched-makedumpfile.txt	2016-10-27 10:28:44.213952179 +0800
@@ -1,4 +1,4 @@
-[127.0.0.1-2016-10-27-10:27:03]# /tmp/makedumpfile -l -d 31 --message-level 31 vmcore vmcore.m.1
+[127.0.0.1-2016-10-27-10:27:03]# /home/dyoung/git/makedumpfile/makedumpfile -l -d 31 --message-level 31 vmcore vmcore.m
 sadump: does not have partition header
 sadump: read dump device as unknown format
 sadump: unknown format
@@ -36,70 +36,76 @@
 
 Memory type  : SPARSEMEM_EX
 
+printing memmap .....
 mem_map (0)
-  mem_map    : ffffea0000000000
+  mem_map    : 0
   pfn_start  : 0
   pfn_end    : 8000
+printing memmap .....
 mem_map (1)
-  mem_map    : ffffea0000200000
+  mem_map    : 0
   pfn_start  : 8000
   pfn_end    : 10000
+printing memmap .....
 mem_map (2)
-  mem_map    : ffffea0000400000
+  mem_map    : 0
   pfn_start  : 10000
   pfn_end    : 18000
+printing memmap .....
 mem_map (3)
-  mem_map    : ffffea0000600000
+  mem_map    : 0
   pfn_start  : 18000
   pfn_end    : 20000
+printing memmap .....
 mem_map (4)
-  mem_map    : ffffea0000800000
+  mem_map    : 0
   pfn_start  : 20000
   pfn_end    : 28000
+printing memmap .....
 mem_map (5)
-  mem_map    : ffffea0000a00000
+  mem_map    : 0
   pfn_start  : 28000
   pfn_end    : 30000
+printing memmap .....
 mem_map (6)
-  mem_map    : ffffea0000c00000
+  mem_map    : 0
   pfn_start  : 30000
   pfn_end    : 38000
+printing memmap .....
 mem_map (7)
-  mem_map    : ffffea0000e00000
+  mem_map    : 0
   pfn_start  : 38000
   pfn_end    : 3ffda
 mmap() is available on the kernel.
 Checking for memory holes          : [100.0 %] |STEP [Checking for memory holes  ] : 0.000030 seconds
-Excluding unnecessary pages        : [100.0 %] \STEP [Excluding unnecessary pages] : 0.007547 seconds
-Checking for memory holes          : [100.0 %] -STEP [Checking for memory holes  ] : 0.000016 seconds
-Checking for memory holes          : [100.0 %] /STEP [Checking for memory holes  ] : 0.000009 seconds
-Excluding unnecessary pages        : [100.0 %] |STEP [Excluding unnecessary pages] : 0.006623 seconds
-Copying data                       : [100.0 %] \STEP [Copying data               ] : 0.184442 seconds
-Copying data                       : [100.0 %] -STEP [Copying data               ] : 0.000041 seconds
+Excluding unnecessary pages        : [100.0 %] \STEP [Excluding unnecessary pages] : 0.000007 seconds
+Checking for memory holes          : [100.0 %] -STEP [Checking for memory holes  ] : 0.000014 seconds
+Checking for memory holes          : [100.0 %] /STEP [Checking for memory holes  ] : 0.000008 seconds
+Excluding unnecessary pages        : [100.0 %] |STEP [Excluding unnecessary pages] : 0.000007 seconds
+Copying data                       : [100.0 %] /STEP [Copying data               ] : 1.421661 seconds
+Copying data                       : [100.0 %] |STEP [Copying data               ] : 0.000036 seconds
 
 Writing erase info...
-offset_eraseinfo: dd5c4e, size_eraseinfo: 0
+offset_eraseinfo: 888c149, size_eraseinfo: 0
 
 Original pages  : 0x0000000000030c7d
-  Excluded pages   : 0x000000000002cf58
-    Pages filled with zero  : 0x00000000000002be
-    Non-private cache pages : 0x0000000000006574
-    Private cache pages     : 0x0000000000000f27
-    User process data pages : 0x0000000000003481
-    Free pages              : 0x000000000002237e
+  Excluded pages   : 0x000000000001d534
+    Pages filled with zero  : 0x000000000001d534
+    Non-private cache pages : 0x0000000000000000
+    Private cache pages     : 0x0000000000000000
+    User process data pages : 0x0000000000000000
+    Free pages              : 0x0000000000000000
     Hwpoison pages          : 0x0000000000000000
-  Remaining pages  : 0x0000000000003d25
-  (The number of pages is reduced to 7%.)
+  Remaining pages  : 0x0000000000013749
+  (The number of pages is reduced to 39%.)
 Memory Hole     : 0x000000000000f35d
 --------------------------------------------------
 Total pages     : 0x000000000003ffda
 
-Cache hit: 29946, miss: 47, hit rate: 99.8%
+Cache hit: 196285, miss: 201, hit rate: 99.9%
 
 
-The dumpfile is saved to vmcore.m.1.
+The dumpfile is saved to vmcore.m.
 
 makedumpfile Completed.
-[root@dhcp-128-65 127.0.0.1-2016-10-27-10:27:03]# ls -lth vmcore.m*
--rw------- 1 root root  14M Oct 27 10:30 vmcore.m.1
--rw------- 1 root root 137M Oct 27 10:28 vmcore.m
+[root@dhcp-128-65 127.0.0.1-2016-10-27-10:27:03]# 

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