[SLOF] [PATCH v2] fat-files: Fix access to FAT32 dir/files when cluster > 16-bits

[Benjamin Herrenschmidt]

>From 3800b503e65e19d0769a5a92c6d9fdcc4aa95f28 Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Date: Thu, 9 Jun 2016 13:01:24 +1000
Subject: 

On FAT32, the directory entry contains a new field providing the
top 16-bits of the cluster number. We didn't use it, thus reading
the wrong sectors when trying to access files or directories
beyond block 0x10000.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---

v2. Remove unrelated change

 slof/fs/packages/fat-files.fs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/slof/fs/packages/fat-files.fs b/slof/fs/packages/fat-files.fs
index d919452..5d578f1 100644
--- a/slof/fs/packages/fat-files.fs
+++ b/slof/fs/packages/fat-files.fs
@@ -73,6 +73,14 @@ INSTANCE VARIABLE next-cluster
     THEN
 ;
 
+\ Read cluster# from directory entry (handle FAT32 extension)
+: get-cluster ( direntry -- cluster# )
+  fat-type @ 20 = IF
+    dup 14 + 2c@ bwjoin 10 lshift
+  ELSE 0 THEN
+  swap 1a + 2c@ bwjoin +
+;
+
 : .time ( x -- )
   base @ >r decimal
   b #split 2 0.r [char] : emit  5 #split 2 0.r [char] : emit  2* 2 0.r
@@ -87,7 +95,7 @@ INSTANCE VARIABLE next-cluster
   dup 0b + c@ 8 and IF drop EXIT THEN \ volume label, not a file
   dup c@ e5 = IF drop EXIT THEN \ deleted file
   cr
-  dup 1a + 2c@ bwjoin [char] # emit 4 0.r space \ starting cluster
+  dup get-cluster [char] # emit 8 0.r space \ starting cluster
   dup 18 + 2c@ bwjoin .date space
   dup 16 + 2c@ bwjoin .time space
   dup 1c + 4c@ bljoin base @ decimal swap a .r base ! space \ size in bytes
@@ -98,6 +106,7 @@ INSTANCE VARIABLE next-cluster
   drop ;
 : .dir-entries ( adr n -- )
   0 ?DO dup i 20 * + dup c@ 0= IF drop LEAVE THEN .dir-entry LOOP drop ;
+
 : .dir ( cluster# -- )
   read-dir BEGIN data @ #data @ 20 / .dir-entries next-cluster @ WHILE
   next-cluster @ read-cluster REPEAT ;
@@ -114,8 +123,10 @@ CREATE dos-name b allot
 : (find-file) ( -- cluster file-len is-dir? true | false )
   data @ BEGIN dup data @ #data @ + < WHILE
   dup dos-name b comp WHILE 20 + REPEAT
-  dup 1a + 2c@ bwjoin swap dup 1c + 4c@ bljoin swap 0b + c@ 10 and 0<> true
+  dup get-cluster
+  swap dup 1c + 4c@ bljoin swap 0b + c@ 10 and 0<> true
   ELSE drop false THEN ;
+
 : find-file ( dir-cluster name len -- cluster file-len is-dir? true | false )
   make-dos-name read-dir BEGIN (find-file) 0= WHILE next-cluster @ WHILE
   next-cluster @ read-cluster REPEAT false ELSE true THEN ;