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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 33DDF180004 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: gwx8oyfnm83kjafdqk6bw5wk4ozjk83n X-HE-Tag: 1743744693-935984 X-HE-Meta: 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 9BmYCKks zIH+D X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/1/25 9:32 AM, Harry Yoo wrote: > On Mon, Mar 31, 2025 at 05:48:18PM +0530, Bhupesh wrote: >> Provide a parallel implementation for get_task_comm() called >> get_task_full_name() which allows the dynamically allocated >> and filled-in task's full name to be passed to interested >> users such as 'gdb'. >> >> Currently while running 'gdb', the 'task->comm' value of a long >> task name is truncated due to the limitation of TASK_COMM_LEN. >> >> For example using gdb to debug a simple app currently which generate >> threads with long task names: >> # gdb ./threadnames -ex "run info thread" -ex "detach" -ex "quit" > log >> # cat log >> >> NameThatIsTooLo >> >> This patch does not touch 'TASK_COMM_LEN' at all, i.e. >> 'TASK_COMM_LEN' and the 16-byte design remains untouched. Which means >> that all the legacy / existing ABI, continue to work as before using >> '/proc/$pid/task/$tid/comm'. >> >> This patch only adds a parallel, dynamically-allocated >> 'task->full_name' which can be used by interested users >> via '/proc/$pid/task/$tid/full_name'. >> >> After this change, gdb is able to show full name of the task: >> # gdb ./threadnames -ex "run info thread" -ex "detach" -ex "quit" > log >> # cat log >> >> NameThatIsTooLongForComm[4662] >> >> Signed-off-by: Bhupesh >> --- >> fs/exec.c | 21 ++++++++++++++++++--- >> include/linux/sched.h | 9 +++++++++ >> 2 files changed, 27 insertions(+), 3 deletions(-) >> >> diff --git a/fs/exec.c b/fs/exec.c >> index f45859ad13ac..4219d77a519c 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1208,6 +1208,9 @@ int begin_new_exec(struct linux_binprm * bprm) >> { >> struct task_struct *me = current; >> int retval; >> + va_list args; >> + char *name; >> + const char *fmt; >> >> /* Once we are committed compute the creds */ >> retval = bprm_creds_from_file(bprm); >> @@ -1348,11 +1351,22 @@ int begin_new_exec(struct linux_binprm * bprm) >> * detecting a concurrent rename and just want a terminated name. >> */ >> rcu_read_lock(); >> - __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name), >> - true); >> + fmt = smp_load_acquire(&bprm->file->f_path.dentry->d_name.name); >> + name = kvasprintf(GFP_KERNEL, fmt, args); >> + if (!name) >> + return -ENOMEM; > Is it safe to return error here, instead of jumping to 'out_unlock' label > and then releasing locks? Ok, let me modify this in v3 to ensure that locks are released properly. >> + me->full_name = name; >> + __set_task_comm(me, fmt, true); >> rcu_read_unlock(); >> } else { >> - __set_task_comm(me, kbasename(bprm->filename), true); >> + fmt = kbasename(bprm->filename); >> + name = kvasprintf(GFP_KERNEL, fmt, args); >> + if (!name) >> + return -ENOMEM; >> + >> + me->full_name = name; >> + __set_task_comm(me, fmt, true); >> } >> >> /* An exec changes our domain. We are no longer part of the thread >> @@ -1399,6 +1413,7 @@ int begin_new_exec(struct linux_binprm * bprm) >> return 0; >> >> out_unlock: >> + kfree(me->full_name); >> up_write(&me->signal->exec_update_lock); >> if (!bprm->cred) >> mutex_unlock(&me->signal->cred_guard_mutex); >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index 56ddeb37b5cd..053b52606652 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -1166,6 +1166,9 @@ struct task_struct { >> */ >> char comm[TASK_COMM_LEN]; >> >> + /* To store the full name if task comm is truncated. */ >> + char *full_name; >> + >> struct nameidata *nameidata; >> >> #ifdef CONFIG_SYSVIPC >> @@ -2007,6 +2010,12 @@ extern void __set_task_comm(struct task_struct *tsk, const char *from, bool exec >> buf; \ >> }) >> >> +#define get_task_full_name(buf, buf_size, tsk) ({ \ >> + BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN); \ >> + strscpy_pad(buf, (tsk)->full_name, buf_size); \ >> + buf; \ >> +}) >> + >> #ifdef CONFIG_SMP >> static __always_inline void scheduler_ipi(void) >> { >> -- >> 2.38.1 >> >> Thanks.