procfs: return right hardlink from /proc/curproc/file

[kib]

Summary

Extract proc_get_binpath() from sysctl_kern_proc_pathname().
Use proc_get_binpath() to get the hardlink right.

PR: 248184

[markj]

sys/kern/kern_proc.c

2264–2265

Perhaps have the caller pass an explicit size instead of assuming MAXPATHLEN. Or at least have a comment above the function noting that it must be MAXPATHLEN bytes in size.

2328

If you write

if (error == 0)
    proc_get_binpath(...);
free(binname, M_TEMP);
if (error != 0)
    return (error);

then the error handling for pget() is not needed.

sys/sys/proc.h

1145

Keep it sorted? It's almost there, except for proc_add_orphan().

[kib]

Add detailed herald comment for proc_get_binpath()
Simplify control flow in sysctl
Reorder proc_ declarations in sys/proc.h

[markj]

sys/kern/kern_proc.c

2231