On 5/30/2019 5:03 PM, Dave Anderson wrote:
>
>
> ----- Original Message -----
>> Hi Dave,
>>
>> I don't know why this difference arises, but with certain kernel configurations,
>> the source file and line information of the schedule() function becomes the
>> following, not "/kernel/sched/core.c".
>>
>> crash> sym schedule
>> ffffffffab0d3666 (T) schedule
>> /share/src/linux-5.0.1/./arch/x86/include/asm/current.h: 15
>
> Yeah, presumably happens because your kernel doesn't have the ftrace nop compiled
> into the beginning of each function. When it does, the first address in the
> schedule function would be in kernel/sched/core.c:
>
> crash> sym schedule
> ffffffffa22b5dc0 (T) schedule /usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c: 3503
> crash> dis -l schedule
> /usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c: 3503
> 0xffffffffa22b5dc0 <schedule>: nopl 0x0(%rax,%rax,1) [FTRACE NOP]
> /usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/./arch/x86/include/asm/current.h: 15
> 0xffffffffa22b5dc5 <schedule+5>: push %rbx
> 0xffffffffa22b5dc6 <schedule+6>: mov %gs:0x15f00,%rbx
> /usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c: 3506
> 0xffffffffa22b5dcf <schedule+15>: mov 0x10(%rbx),%rax
> 0xffffffffa22b5dd3 <schedule+19>: test %rax,%rax
> 0xffffffffa22b5dd6 <schedule+22>: je 0xffffffffa22b5de2 <schedule+34>
> ...
Ah, I see. Thanks! I think it is CONFIG_DYNAMIC_FTRACE,
which the config does not have.
$ grep FTRACE config-5.0.1
CONFIG_HAVE_KPROBES_ON_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y
CONFIG_FTRACE=y
# CONFIG_FTRACE_SYSCALLS is not set
# CONFIG_FTRACE_STARTUP_TEST is not set
Thanks,
Kazu
>
> If ftrace is not enabled, then it would show asm/current.h because the first instruction
> in schedule() is the evaluation of "current":
>
> asmlinkage __visible void __sched schedule(void)
> {
> struct task_struct *tsk = current;
>
> which is #define'd in asm/current.h:
>
> #define get_current() (current_thread_info()->task)
> #define current get_current()
>
> Anyway, I'll take a look and test the patch tomorrow.
>
> Thanks,
> Dave
>
>>
>> This causes the "sys -c" option not to print the information of system calls,
>> and makes it very slow.
>>
>> crash> sys -c | sh -c 'time cat'
>> NUM SYSTEM CALL FILE AND LINE NUMBER
>> 0 __x64_sys_read
>> 1 __x64_sys_write
>> 2 __x64_sys_open
>> ...
>> 333 __x64_sys_io_pgetevents
>> 334 __x64_sys_rseq
>>
>> real 2m32.669s
>> user 0m0.002s
>> sys 0m0.022s
>>
>> With this patch, the option can print the information in not too long time:
>>
>> crash> sys -c | sh -c 'time cat'
>> NUM SYSTEM CALL FILE AND LINE NUMBER
>> 0 __x64_sys_read ../fs/read_write.c: 588
>> 1 __x64_sys_write ../fs/read_write.c: 610
>> 2 __x64_sys_open ../fs/open.c: 1079
>> ...
>> 333 __x64_sys_io_pgetevents ../fs/aio.c: 2139
>> 334 __x64_sys_rseq ../kernel/rseq.c: 308
>>
>> real 0m10.905s
>> user 0m0.000s
>> sys 0m0.024s
>>
>> Also, in dump_sys_call_table(), it looks like there is no need to call
>> get_build_directory() for each system call, so moving it out of the loop
>> makes it faster.
>>
>> [without moving the get_build_directory()]
>> real 0m15.862s
>> user 0m0.003s
>> sys 0m0.020s
>>
>> Signed-off-by: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx>
>> ---
>> kernel.c | 2 +-
>> symbols.c | 2 +-
>> 2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel.c b/kernel.c
>> index db25f22e4ec6..22909d28cefc 100644
>> --- a/kernel.c
>> +++ b/kernel.c
>> @@ -5679,6 +5679,7 @@ dump_sys_call_table(char *spec, int cnt)
>>
>> fprintf(fp, "%s", sys_call_hdr);
>>
>> + get_build_directory(buf2);
>> for (i = 0, sct = sys_call_table; i < NR_syscalls; i++, sct++) {
>> if (!(scp = value_symbol(*sct))) {
>> if (confirmed || CRASHDEBUG(1)) {
>> @@ -5710,7 +5711,6 @@ dump_sys_call_table(char *spec, int cnt)
>> */
>> sp = value_search(*sct, NULL);
>> spn = next_symbol(NULL, sp);
>> - get_build_directory(buf2);
>>
>> for (addr = *sct; sp && spn && (addr < spn->value); addr++) {
>> BZERO(buf1, BUFSIZE);
>> diff --git a/symbols.c b/symbols.c
>> index 863d1f0a8e25..3ce8692fd397 100644
>> --- a/symbols.c
>> +++ b/symbols.c
>> @@ -4296,7 +4296,7 @@ get_build_directory(char *buf)
>> get_line_number(symbol_value("do_schedule"), buf, FALSE);
>> else
>> return NULL;
>> - if ((p = strstr(buf, "/kernel/")))
>> + if ((p = strstr(buf, "/kernel/")) || (p = strstr(buf, "/./arch/")))
>> *p = NULLCHAR;
>> else
>> return(NULL);
>> --
>> 2.18.1
>>
>
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