# ucode_seccomp.txt -- the pc set of iris/UCodeSeccomp.v, for tools/gen_ucode.py.

#

# tools/ucode_manifest.json binds this spec to iris/UCodeSeccomp.v; `make

# gen-ucode` rewrites that file from it, and `make check-ucode` fails if it

# moved.

#

# seccomp (user/seccomp.c, new at a083670) is the program that runs its

# argument under a syscall mask: fork; the child ANDs its mask with the

# complement of {SYS_kill 6, SYS_open 15, SYS_mknod 17, SYS_unlink 18,

# SYS_link 19, SYS_mkdir 20} (upstream 7b2c1b1; the lui/addi pair at

# main+0x1c builds 0xffff_ffff_ffe1_7fbf) and execs argv[1] with argv+1;

# the parent waits and exits 0. Its four diagnostics (usage, fork failed, seccomp failed, exec %s

# failed) all go through fprintf on fd 2, with at most a %s. It never

# uses printf.

#

# Unreachable branches inside a listed function are kept (ucode_cat.txt's

# rule); whole functions never entered are left out, with the reason.

note This catalog covers seccomp as it runs: start, main's fork / mask /

note exec / wait, the six syscall stubs main issues, and the

note fprintf cone under its four diagnostics.

# ---- the program ------------------------------------------------------

func start

func main

# ---- the fprintf cone (all four diagnostics, fd 2) --------------------

func fprintf

func vprintf

func putc

# ---- the syscall stubs it issues --------------------------------------

func fork

func exit

func wait

func exec

func seccomp

func write

# ---- and what is deliberately absent ---------------------------------

skipfunc printf unreachable: every diagnostic is an fprintf(2, ...)

skipfunc printint unreachable: vprintf reaches it only from the %d/%u/%x arms, and seccomp's only conversion is %s

skipfunc malloc unreachable: seccomp allocates nothing

skipfunc free unreachable: seccomp allocates nothing

skipfunc sbrk unreachable: only malloc calls it

skipfunc sbrklazy unreachable: only malloc calls it

skipfunc sys_sbrk unreachable: only malloc calls it

skipfunc gets unreachable: seccomp reads nothing

skipfunc stat unreachable: seccomp never stats

skipfunc fstat unreachable: only stat calls it

skipdefault library function or other syscall stub that seccomp never calls