[Bug breakpoints/29155] New: After disabling "detach-on-fork" , syscalls are not catched in both parent and child

[Bug breakpoints/29155] New: After disabling "detach-on-fork" , syscalls are not catched in both parent and child

[theojehl76 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29155

            Bug ID: 29155
           Summary: After disabling "detach-on-fork" , syscalls are not
                    catched in both parent and child
           Product: gdb
           Version: 12.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: breakpoints
          Assignee: unassigned at sourceware dot org
          Reporter: theojehl76 at gmail dot com
  Target Milestone: ---

When "detach-on-fork" is set to off, GDB is not able to catch syscalls anymore,
this behavior started from GDB 10, GDB 9.2 is still able to track syscalls with
"detach-on-fork" disabled

example:

#include<stdio.h>
#include<stdlib.h>
#include<sys/mman.h>
#include<unistd.h>
#include<sys/ptrace.h>
int main(){
        pid_t pid = fork();

        if(pid == 0){
                write(1, "child", 5);
                while(1);
        }
        if(pid > 0){
                write(1, "parent", 6);
        }
        return 0;
}


Expected behavior:

(gdb) set detach-on-fork off
(gdb) catch syscall write
Catchpoint 1 (syscall 'write' [64])
(gdb) r
Starting program
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
[Detaching after fork from child process 2167]
child
Catchpoint 1 (call to syscall write), 0x0000fffff7ee7c50 in __GI___libc_write
(fd=1, buf=0xaaaaaaaa0858, nbytes=6) at ../sysdeps/unix/sysv/linux/write.c:26
26      ../sysdeps/unix/sysv/linux/write.c: No such file or directory.



Actual behavior:

(gdb) set detach-on-fork off
(gdb) catch syscall write
Catchpoint 1 (syscall 'write' [64])
(gdb) r
Starting program
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
[New inferior 2 (process 2184)]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
parent[Inferior 1 (process 2182) exited normally]


This was tested on Linux running on X86_64 and AARCH64 with the same results

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[Bug breakpoints/29155] After disabling "detach-on-fork" , syscalls are not catched in both parent and child

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29155

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-05-03
                 CC|                            |tromey at sourceware dot org
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
We were discussing this on irc.
For me this sometimes works in the parent process, but
also sometimes fails.

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[Bug breakpoints/29155] After disabling "detach-on-fork" , syscalls are not catched in both parent and child

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29155

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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