kernel: stat/fsstat/isatty syscalls, and O_APPEND

Four things userland had no way to ask for:

- SYS_STAT: type, link count, size and inode for a path. The trap needs HL
  for its dispatch table, so a call taking both a path and an output buffer
  passes a request block - the shape SYS_NET already established. usr/stat.h
  wraps it, header-only like sock.h, because the block must live in the
  caller's RAM.
- SYS_FSSTAT: blocks/inodes, total and free. The bitmaps are already cached
  write-through in fs_bmbuf, so this is the popcount boot_fs already prints.
- SYS_ISATTY: is this process's stdin the console? The shell needs it to tell
  an interactive session from a script.
- O_APPEND: open a file positioned at EOF. There is no seek syscall, so this
  is the only way to add to a file - without it nothing running ON the Game
  Boy can build a multi-line file, shell scripts included.

Together these back ls -l, df, and `>>`.

1 files changed, 24 insertions, 1 deletions

diff --git a/include/gbos.inc b/include/gbos.inc
index eabdcec..76981da 100644
--- a/include/gbos.inc
+++ b/include/gbos.inc
@@ -123,6 +123,9 @@ DEF PROC_SIZE   RB 0
 
 DEF KILL_CODE   EQU 137 ; exit status of a killed process (128 + SIGKILL)
 
+DEF O_READ   EQU 0
+DEF O_WRITE  EQU 1
+DEF O_APPEND EQU 2       ; write, keeping what is there (pos starts at EOF)
 DEF STD_CONSOLE EQU $FF
 
 ; -----------------------------------------------------------------------------
@@ -165,7 +168,20 @@ DEF SYS_NET     EQU 33   ; socket layer                    (DE=&netreq -> A=resu
 DEF SYS_SLEEP   EQU 34   ; cooperative delay               (B = 1/64-second units)
 DEF SYS_POLLCON EQU 35   ; poll console ring (link-injected -> A=byte or 0)
 DEF SYS_UPTIME  EQU 36   ; copy the 64 Hz tick counter (4B LE) to [DE]
-DEF SYS_MAX     EQU 37
+DEF SYS_STAT    EQU 37   ; stat a path                     (DE=&statreq -> A=0/$FF)
+DEF SYS_FSSTAT  EQU 38   ; filesystem totals               (DE=buf[4] -> A=0)
+DEF SYS_ISATTY  EQU 39   ; is stdin the console?           (-> A=1/0)
+DEF SYS_MAX     EQU 40
+
+; ---- SYS_STAT request block (see fs.asm sys_stat) ---------------------------
+; The syscall trap needs HL for its dispatch table, so a call that takes both a
+; path and an output buffer passes a request block, like SYS_NET does.
+DEF SR_PATH  EQU 0       ; 2: pointer to the path (in)
+DEF SR_TYPE  EQU 2       ; 1: IT_FILE / IT_DIR    (out)
+DEF SR_NLINK EQU 3       ; 1                      (out)
+DEF SR_SIZE  EQU 4       ; 2: bytes, little-endian(out)
+DEF SR_INO   EQU 6       ; 1: inode number        (out)
+DEF SR_SIZE_ EQU 7       ; sizeof(statreq)
 
 ; ---- socket layer (SYS_NET) --------------------------------------------------
 ; netreq struct (in caller RAM; DE points to it):
@@ -307,5 +323,12 @@ DEF PROG_CP     EQU 35
 DEF PROG_NC     EQU 36
 DEF PROG_HTTPD  EQU 37
 DEF PROG_IRCD   EQU 38
+DEF PROG_DF     EQU 39
+DEF PROG_MV     EQU 40
+DEF PROG_SLEEP  EQU 41
+DEF PROG_TEE    EQU 42
+DEF PROG_TAIL   EQU 43
+DEF PROG_HELP   EQU 44
+DEF PROG_POWEROFF EQU 45
 
     ENDC