Commit 7e40f2ab authored by Balbir Singh's avatar Balbir Singh Committed by Linus Torvalds

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: default avatarBalbir 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fc83815c
......@@ -31,7 +31,7 @@
*/
#define TASKSTATS_VERSION 3
#define TASKSTATS_VERSION 4
#define TS_COMM_LEN 32 /* should be >= TASK_COMM_LEN
* in linux/sched.h */
......@@ -66,7 +66,7 @@ struct taskstats {
/* Delay waiting for cpu, while runnable
* count, delay_total NOT updated atomically
*/
__u64 cpu_count;
__u64 cpu_count __attribute__((aligned(8)));
__u64 cpu_delay_total;
/* Following four fields atomically updated using task->delays->lock */
......@@ -101,14 +101,17 @@ struct taskstats {
/* Basic Accounting Fields start */
char ac_comm[TS_COMM_LEN]; /* Command name */
__u8 ac_sched; /* Scheduling discipline */
__u8 ac_sched __attribute__((aligned(8)));
/* Scheduling discipline */
__u8 ac_pad[3];
__u32 ac_uid; /* User ID */
__u32 ac_uid __attribute__((aligned(8)));
/* User ID */
__u32 ac_gid; /* Group ID */
__u32 ac_pid; /* Process ID */
__u32 ac_ppid; /* Parent process ID */
__u32 ac_btime; /* Begin time [sec since 1970] */
__u64 ac_etime; /* Elapsed time [usec] */
__u64 ac_etime __attribute__((aligned(8)));
/* Elapsed time [usec] */
__u64 ac_utime; /* User CPU time [usec] */
__u64 ac_stime; /* SYstem CPU time [usec] */
__u64 ac_minflt; /* Minor Page Fault Count */
......
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