Lots of kretprobe_trampoline_holder in backtrace

[Peter Teoh]

Using the following script:

probe kernel.function("*@fs/open.c").call {
        printf("===>%s\n", probefunc());
        print_backtrace();
        printf("\n");
}

probe kernel.function("*@fs/open.c").return {
        printf("<===%s\n", probefunc());
        printf("\n");
}

The output below.   As noted, there is a lot of information hidden by
the presence of breakpoints, which are output as
kretprobe_trampoline_holder*.   Is it not more logical to display the
ORIGINAL function, instead of the breakpoints on where we are seeing
kretprobe_trampoline_holder right now.....just like normal gdb
backtrace information.   Shown below, if the breakpoints so happened
to embed one another, there is a lot of information lost, resulting in
a lot of not-so-useful "kretprobe_trampoline_holder" stacking up one
another.

===>sys_open
 0xc04728c7 : sys_open+0x1/0x26

===>do_sys_open
 0xc04727ec : do_sys_open+0x1/0xb7
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33

===>get_unused_fd_flags
 0xc0472523 : get_unused_fd_flags+0x1/0xd0
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33

<===get_unused_fd_flags

===>do_filp_open
 0xc04727b7 : do_filp_open+0x1/0x35
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33

===>nameidata_to_filp
 0xc0472784 : nameidata_to_filp+0x1/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33

===>__dentry_open
 0xc04725ff : __dentry_open+0x1/0x185
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33
 0xc06377a6 : kretprobe_trampoline_holder+0x3/0x33

<===__dentry_open

<===nameidata_to_filp

<===do_filp_open



-- 
Regards,
Peter Teoh