fix: better compatibility under busybox, silence buggy unzlma versions (fix #432)

DEVELOPMENT.md

@@ -167,6 +167,7 @@ Common traps to avoid:
 | `xargs` | `-r` (no-op if empty, GNU only) | Guard with a prior `[ -n "..." ]` check, or accept the harmless empty invocation |
 | `readlink` | `-f` (canonicalize, GNU only) | Use only in Linux-specific code paths, or reimplement with `cd`/`pwd` |
 | `dd` | `iflag=`, `oflag=` (GNU only) | Use only in Linux-specific code paths (e.g. `/dev/cpu/*/msr`) |
+| `base64` | `-w N` (set line-wrap width, GNU only; BusyBox doesn't support it) | Pipe through `tr -d '\n'` to remove newlines instead of `-w0` |
 
 When a tool genuinely has no portable equivalent, restrict the non-portable call to a platform-specific code path (i.e. inside a BSD-only or Linux-only branch) and document why.
 

src/libs/300_kernel_extract.sh

@@ -88,7 +88,9 @@ try_decompress() {
         fi
         pos=${pos%%:*}
         # shellcheck disable=SC2086
-        tail -c+$pos "$6" 2>/dev/null | $3 $4 >"$g_kerneltmp" 2>/dev/null
+        # wrap in subshell so that if $3 segfaults (e.g. old BusyBox unlzma on random data),
+        # the "Segmentation fault" message printed by the shell goes to /dev/null
+        (tail -c+$pos "$6" 2>/dev/null | $3 $4 >"$g_kerneltmp" 2>/dev/null) 2>/dev/null
         ret=$?
         if [ ! -s "$g_kerneltmp" ]; then
             # don't rely on $ret, sometimes it's != 0 but worked

src/main.sh

@@ -35,7 +35,7 @@ if [ -n "$g_mockme" ] && [ "$opt_mock" = 1 ]; then
         # not a useless use of cat: gzipping cpuinfo directly doesn't work well
         # shellcheck disable=SC2002
         if command -v "base64" >/dev/null 2>&1; then
-            g_mock_cpuinfo="$(cat /proc/cpuinfo | gzip -c | base64 -w0)"
+            g_mock_cpuinfo="$(cat /proc/cpuinfo | gzip -c | base64 | tr -d '\n')"
         elif command -v "uuencode" >/dev/null 2>&1; then
             g_mock_cpuinfo="$(cat /proc/cpuinfo | gzip -c | uuencode -m - | grep -Fv 'begin-base64' | grep -Fxv -- '====' | tr -d "\n")"
         fi