The map
One line per function: file : function — what it does [ch]. Add your own as you go; this is the version at the end of the series. Pinned to 6.12 LTS.
arch/x86/entry/entry_64.S : entry_SYSCALL_64 — syscall entry; saves pt_regs [1]
arch/x86/entry/common.c : do_syscall_64 — seccomp/ptrace/tracepoint, then x64_sys_call [1]
kernel/entry/common.c : exit_to_user_mode_loop — resched, signals, task_work before returning [1,12]
fs/open.c : do_sys_openat2 — flags, fd allocation, do_filp_open [2]
fs/namei.c : path_openat — RCU-walk then ref-walk [2]
fs/namei.c : link_path_walk — component loop [2]
fs/namei.c : lookup_fast / lookup_slow — dcache hit / filesystem lookup [2]
fs/dcache.c : __d_lookup_rcu — the hash lookup [2]
fs/open.c : do_dentry_open — f_op->open; the file is live [2]
kernel/fork.c : kernel_clone — fork/clone entry [3]
kernel/fork.c : copy_process — build the child task [3]
kernel/fork.c : dup_mmap — copy VMAs; PTEs made read-only for COW [3,5]
fs/exec.c : bprm_execve / exec_binprm — find the handler [3]
fs/exec.c : begin_new_exec — point of no return [3]
fs/binfmt_elf.c : load_elf_binary — map segments, interp, auxv; start_thread [3]
kernel/sched/core.c : __schedule — pick and switch [4]
kernel/sched/fair.c : update_curr — charge weighted vruntime [4]
kernel/sched/fair.c : pick_eevdf — eligible + earliest deadline [4]
kernel/sched/fair.c : place_entity — vruntime on wakeup, lag preserved [4]
kernel/sched/core.c : context_switch — switch_mm, switch_to [4]
arch/x86/mm/fault.c : exc_page_fault — #PF entry; CR2 [5]
arch/x86/mm/fault.c : do_user_addr_fault — VMA lookup, permission, handle_mm_fault [5]
mm/memory.c : __handle_mm_fault — page-table walk/alloc [5]
mm/memory.c : handle_pte_fault — anon / file / COW / swap dispatch [5]
mm/memory.c : do_anonymous_page — zero page or new folio [5]
mm/memory.c : do_wp_page — copy-on-write or reuse [5]
mm/filemap.c : filemap_fault — page cache from the fault side [5]
mm/filemap.c : filemap_read — read(): folio batch, copy to user [6]
mm/readahead.c : page_cache_ra_unbounded — the readahead window [6]
block/blk-core.c : submit_bio — into the block layer [6]
net/socket.c : __sys_connect_file — security_socket_connect; ops->connect [7]
net/ipv4/af_inet.c : __inet_stream_connect — pre_connect (cgroup BPF), connect, wait [7]
net/ipv4/tcp_ipv4.c : tcp_v4_pre_connect — BPF_CGROUP_RUN_PROG_INET4_CONNECT [7]
kernel/bpf/cgroup.c : __cgroup_bpf_run_filter_sock_addr — run effective programs; may rewrite [7,11]
net/ipv4/tcp_ipv4.c : tcp_v4_connect — route (commit), port, state SYN_SENT [7]
net/ipv4/tcp_output.c : tcp_connect — build and send the SYN; arm retransmit [7]
net/ipv4/tcp_output.c : __tcp_transmit_skb — TCP header; queue_xmit [7,8]
net/ipv4/ip_output.c : __ip_local_out — NF_INET_LOCAL_OUT [7,8]
net/ipv4/ip_output.c : ip_finish_output — BPF_CGROUP_RUN_PROG_INET_EGRESS [7,8]
net/core/dev.c : __dev_queue_xmit — TC egress, qdisc, driver [8]
net/ipv4/tcp.c : tcp_sendmsg_locked — user data into skbs; push [8]
net/ipv4/tcp_output.c : tcp_write_xmit — cwnd, rwnd, pacing, TSQ [8]
net/core/dev.c : net_rx_action — NAPI poll loop [9]
net/core/dev.c : __netif_receive_skb_core — taps, TC ingress, protocol demux [9]
net/ipv4/ip_input.c : ip_rcv / ip_local_deliver — PRE_ROUTING, route, LOCAL_IN [9]
net/ipv4/tcp_ipv4.c : tcp_v4_rcv — socket lookup; backlog or do_rcv [9]
net/ipv4/tcp_input.c : tcp_rcv_established — the fast path [9]
net/ipv4/tcp.c : tcp_recvmsg_locked — copy to user; window update [9]
kernel/bpf/syscall.c : bpf_prog_load — load; bpf_check; select_runtime [10]
kernel/bpf/verifier.c : do_check — symbolic execution over all paths [10]
kernel/bpf/verifier.c : is_state_visited — pruning [10]
arch/x86/net/bpf_jit_comp.c : bpf_int_jit_compile — the JIT [10]
security/security.c : call_int_hook (security_*) — static-call slots per LSM [11]
kernel/cgroup/cgroup.c : cgroup_migrate_execute — swap css_set; controllers' attach [11]
kernel/bpf/cgroup.c : update_effective_progs — ancestors' programs for every descendant [11]
kernel/signal.c : __send_signal_locked — queue; complete_signal [12]
kernel/signal.c : get_signal / handle_signal — dequeue; set up the user frame [12]
kernel/time/hrtimer.c : hrtimer_interrupt — expiry; callbacks; wakeups [12]
kernel/time/timer.c : run_timer_softirq — the timer wheel [12]
kernel/rcu/tree.c : synchronize_rcu — wait a grace period [12]