On 31.03.2017 08:40, Tommi Rantala wrote:
The only thing that I can think of would be a rogue ptr in the bios
table, but that seems unlikely. Tommi, can you put strace of x86info
-mp somewhere?
That will confirm/deny whether we're at least asking the kernel to do
sane things.
Indeed the bug happens when reading from /dev/mem:
https://pastebin.com/raw/ZEJGQP1X
# strace -f -y x86info -mp
[...]
open("/dev/mem", O_RDONLY) = 3</dev/mem>
lseek(3</dev/mem>, 1038, SEEK_SET) = 1038
read(3</dev/mem>, "\300\235", 2) = 2
lseek(3</dev/mem>, 646144, SEEK_SET) = 646144
read(3</dev/mem>,
"\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3</dev/mem>, 1043, SEEK_SET) = 1043
read(3</dev/mem>, "w\2", 2) = 2
lseek(3</dev/mem>, 645120, SEEK_SET) = 645120
read(3</dev/mem>,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3</dev/mem>, 654336, SEEK_SET) = 654336
read(3</dev/mem>,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3</dev/mem>, 983040, SEEK_SET) = 983040
read(3</dev/mem>,
"IFE$\245S\0\0\1\0\0\0\0\360y\0\0\360\220\260\30\237{=\23\10\17\0000\276\17\0"...,
65536) = 65536
lseek(3</dev/mem>, 917504, SEEK_SET) = 917504
read(3</dev/mem>,
"\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377\377"...,
65536) = 65536
lseek(3</dev/mem>, 524288, SEEK_SET) = 524288
read(3</dev/mem>, <unfinished ...>) = ?
+++ killed by SIGSEGV +++
That last read is done in mptable.c:347, trying to read GROPE_AREA1.
# ./x86info --debug
x86info v1.31pre
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 0
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 1
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 2
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 3
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 0
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 1
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 2
get_intel_topology:
Siblings: 2
Physical Processor ID: 0
Processor Core ID: 3
Found 8 identical CPUs
EBDA points to: 9dc0
EBDA segment ptr: 9dc00
Segmentation fault
If I comment out the GROPE_AREA1 read, the same kernel bug still happens
with the GROPE_AREA2 read.
Removing both GROPE_AREA1 and GROPE_AREA2 reads avoids the crash:
$ git diff
diff --git a/mptable.c b/mptable.c
index 480f19b..00fff35 100644
--- a/mptable.c
+++ b/mptable.c
@@ -342,6 +342,7 @@ static int apic_probe(unsigned long* paddr)
}
/* search additional memory */
+ /*
target = GROPE_AREA1;
seekEntry(target);
if (readEntry(buffer, GROPE_SIZE)) {
@@ -371,6 +372,7 @@ static int apic_probe(unsigned long* paddr)
return 6;
}
}
+ */
*paddr = (unsigned long)0;
return 0;
# ./x86info -mp
x86info v1.31pre
Found 8 identical CPUs
Extended Family: 0 Extended Model: 5 Family: 6 Model: 94 Stepping: 3
Type: 0 (Original OEM)
CPU Model (x86info's best guess): Unknown model.
Processor name string (BIOS programmed): Intel(R) Core(TM) i7-6820HQ CPU
@ 2.70GHz
Total processor threads: 8
This system has 1 quad-core processor with hyper-threading (2 threads
per core) running at an estimated 2.70GHz
#
-Tommi
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