Taskstats fix the structure members alignment issue
We broke the the alignment of members of taskstats to the 8 byte boundary
with the CSA patches. In the current kernel, the taskstats structure is
not suitable for use by 32 bit applications in a 64 bit kernel.
On x86_64
Offsets of taskstats' members (64 bit kernel, 64 bit application)
@taskstats'offsetof[@taskstats'indices] = (
0, # version
4, # ac_exitcode
8, # ac_flag
9, # ac_nice
16, # cpu_count
24, # cpu_delay_total
32, # blkio_count
40, # blkio_delay_total
48, # swapin_count
56, # swapin_delay_total
64, # cpu_run_real_total
72, # cpu_run_virtual_total
80, # ac_comm
112, # ac_sched
113, # ac_pad
116, # ac_uid
120, # ac_gid
124, # ac_pid
128, # ac_ppid
132, # ac_btime
136, # ac_etime
144, # ac_utime
152, # ac_stime
160, # ac_minflt
168, # ac_majflt
176, # coremem
184, # virtmem
192, # hiwater_rss
200, # hiwater_vm
208, # read_char
216, # write_char
224, # read_syscalls
232, # write_syscalls
240, # read_bytes
248, # write_bytes
256, # cancelled_write_bytes
);
Offsets of taskstats' members (64 bit kernel, 32 bit application)
@taskstats'offsetof[@taskstats'indices] = (
0, # version
4, # ac_exitcode
8, # ac_flag
9, # ac_nice
12, # cpu_count
20, # cpu_delay_total
28, # blkio_count
36, # blkio_delay_total
44, # swapin_count
52, # swapin_delay_total
60, # cpu_run_real_total
68, # cpu_run_virtual_total
76, # ac_comm
108, # ac_sched
109, # ac_pad
112, # ac_uid
116, # ac_gid
120, # ac_pid
124, # ac_ppid
128, # ac_btime
132, # ac_etime
140, # ac_utime
148, # ac_stime
156, # ac_minflt
164, # ac_majflt
172, # coremem
180, # virtmem
188, # hiwater_rss
196, # hiwater_vm
204, # read_char
212, # write_char
220, # read_syscalls
228, # write_syscalls
236, # read_bytes
244, # write_bytes
252, # cancelled_write_bytes
);
This is one way to solve the problem without re-arranging structure members
is to pack the structure. The patch adds an __attribute__((aligned(8))) to
the taskstats structure members so that 32 bit applications using taskstats
can work with a 64 bit kernel.
Using __attribute__((packed)) would break the 64 bit alignment of members.
The fix was tested on x86_64. After the fix, we got
Offsets of taskstats' members (64 bit kernel, 64 bit application)
@taskstats'offsetof[@taskstats'indices] = (
0, # version
4, # ac_exitcode
8, # ac_flag
9, # ac_nice
16, # cpu_count
24, # cpu_delay_total
32, # blkio_count
40, # blkio_delay_total
48, # swapin_count
56, # swapin_delay_total
64, # cpu_run_real_total
72, # cpu_run_virtual_total
80, # ac_comm
112, # ac_sched
113, # ac_pad
120, # ac_uid
124, # ac_gid
128, # ac_pid
132, # ac_ppid
136, # ac_btime
144, # ac_etime
152, # ac_utime
160, # ac_stime
168, # ac_minflt
176, # ac_majflt
184, # coremem
192, # virtmem
200, # hiwater_rss
208, # hiwater_vm
216, # read_char
224, # write_char
232, # read_syscalls
240, # write_syscalls
248, # read_bytes
256, # write_bytes
264, # cancelled_write_bytes
);
Offsets of taskstats' members (64 bit kernel, 32 bit application)
@taskstats'offsetof[@taskstats'indices] = (
0, # version
4, # ac_exitcode
8, # ac_flag
9, # ac_nice
16, # cpu_count
24, # cpu_delay_total
32, # blkio_count
40, # blkio_delay_total
48, # swapin_count
56, # swapin_delay_total
64, # cpu_run_real_total
72, # cpu_run_virtual_total
80, # ac_comm
112, # ac_sched
113, # ac_pad
120, # ac_uid
124, # ac_gid
128, # ac_pid
132, # ac_ppid
136, # ac_btime
144, # ac_etime
152, # ac_utime
160, # ac_stime
168, # ac_minflt
176, # ac_majflt
184, # coremem
192, # virtmem
200, # hiwater_rss
208, # hiwater_vm
216, # read_char
224, # write_char
232, # read_syscalls
240, # write_syscalls
248, # read_bytes
256, # write_bytes
264, # cancelled_write_bytes
);
Signed-off-by: 
Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Cc: Shailabh Nagar <nagar@watson.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: 
Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: 
Linus Torvalds <torvalds@linux-foundation.org>
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