[PATCH] scripts: Increase BUILD_MIN_BIOSTABLE for auto-sized and 128KB ROMs

When CONFIG_ROM_SIZE is left at 0 (auto), checkrom.py will automatically
determine the ROM size based on the actual binary size (up to 256KB).
However, layoutrom.py only increased BUILD_MIN_BIOSTABLE to 8192 when
CONFIG_ROM_SIZE was explicitly set to 256 or larger. This meant that if
the code grew large enough to require a 256KB ROM, layoutrom.py would
still use the smaller 2048-byte F-segment reserve, potentially causing
resource allocation problems in case of a big number of boot entries.
Also, 128KB ROMs should have a larger 4096-byte F-segment reserve.

Fix this erroneous behavior for non-specified CONFIG_ROM_SIZE case by
calculating the total raw size of all sections that will be placed in
the ROM. This raw sum underestimates the final binary size by roughly
5% due to alignment padding and relocation tables, so if it exceeds
64KB we can reliably conclude the final ROM will be at least 128KB and
set BUILD_MIN_BIOSTABLE = 4096; if it exceeds 128KB the final ROM will
be 256KB and we set BUILD_MIN_BIOSTABLE = 8192, matching the behavior
for explicitly configured 128KB and 256KB ROMs.

Signed-off-by: Mike Banon <mikebdp2@gmail.com>
---
 scripts/layoutrom.py | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/scripts/layoutrom.py b/scripts/layoutrom.py
index abebf021..4fe75ceb 100755
--- a/scripts/layoutrom.py
+++ b/scripts/layoutrom.py
@@ -651,10 +651,6 @@ def main():
     # Read kconfig config file
     config = scanconfig(cfgfile)

-    # larger roms have more room in the f-segment due to moving out 32bit code
-    if config.get('CONFIG_ROM_SIZE') >= 256:
-        BUILD_MIN_BIOSTABLE = 8192
-
     # Figure out which sections to keep.
     allsections = info16[0] + info32seg[0] + info32flat[0]
     symbols = {'16': info16[1], '32seg': info32seg[1], '32flat': info32flat[1]}
@@ -670,6 +666,20 @@ def main():
     keepsections = findReachable(anchorsections, checkKeep, symbols)
     sections = [section for section in allsections if section in keepsections]

+    # larger roms have more room in the f-segment due to moving out 32bit code
+    if config.get('CONFIG_ROM_SIZE') >= 128:
+        BUILD_MIN_BIOSTABLE = 4096
+    if config.get('CONFIG_ROM_SIZE') >= 256:
+        BUILD_MIN_BIOSTABLE = 8192
+    if config.get('CONFIG_ROM_SIZE') == 0:
+        sections_size = 0
+        for section in sections:
+            sections_size += section.size
+        if sections_size >  64 * 1024:
+            BUILD_MIN_BIOSTABLE = 4096
+        if sections_size > 128 * 1024:
+            BUILD_MIN_BIOSTABLE = 8192
+
     # Separate 32bit flat into runtime, init, and special variable parts
     anchorsections = [
         section for section in sections
-- 
2.53.0
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