[SeaBIOS] [PATCH 08/12] build: Support declaring 32bit C functions that must reside in the f-segment

[Kevin O'Connor]

Add support for a FUNCFSEG macro that will force a "32bit flat" C
function to be located in the f-segment.  This is useful for 32bit
code with inline assembler that thunks to 16bit mode.

Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
---
 scripts/layoutrom.py | 16 +++++++++++-----
 src/types.h          |  4 ++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/scripts/layoutrom.py b/scripts/layoutrom.py
index 2454920..dd770fe 100755
--- a/scripts/layoutrom.py
+++ b/scripts/layoutrom.py
@@ -197,11 +197,14 @@ def doLayout(sections, config, genreloc):
         textsections + rodatasections + datasections, sec16_start
         , segoffset=BUILD_BIOS_ADDR)
 
-    # Determine "fseg memory" data positions
-    sections32fseg = getSectionsCategory(sections, '32fseg')
+    # Determine 32bit "fseg memory" data positions
+    sections32textfseg = getSectionsCategory(sections, '32textfseg')
+    sec32textfseg_start, sec32textfseg_align = setSectionsStart(
+        sections32textfseg, sec32seg_start, 16)
 
+    sections32fseg = getSectionsCategory(sections, '32fseg')
     sec32fseg_start, sec32fseg_align = setSectionsStart(
-        sections32fseg, sec32seg_start, 16
+        sections32fseg, sec32textfseg_start, 16
         , segoffset=BUILD_BIOS_ADDR)
 
     # Determine 32flat runtime positions
@@ -274,13 +277,14 @@ def doLayout(sections, config, genreloc):
     # Print statistics
     size16 = BUILD_BIOS_ADDR + BUILD_BIOS_SIZE - sec16_start
     size32seg = sec16_start - sec32seg_start
-    size32fseg = sec32seg_start - sec32fseg_start
+    size32textfseg = sec32seg_start - sec32textfseg_start
+    size32fseg = sec32textfseg_start - sec32fseg_start
     size32flat = sec32fseg_start - sec32flat_start
     size32init = sec32flat_start - sec32init_start
     sizelow = li.sec32low_end - li.sec32low_start
     print("16bit size:           %d" % size16)
     print("32bit segmented size: %d" % size32seg)
-    print("32bit flat size:      %d" % size32flat)
+    print("32bit flat size:      %d" % (size32flat + size32textfseg))
     print("32bit flat init size: %d" % size32init)
     print("Lowmem size:          %d" % sizelow)
     print("f-segment var size:   %d" % size32fseg)
@@ -659,6 +663,8 @@ def main():
             section.category = '32low'
         elif section.name.startswith('.data.varfseg.'):
             section.category = '32fseg'
+        elif section.name.startswith('.text.32fseg.'):
+            section.category = '32textfseg'
         elif section.name.startswith('.fixedaddr.'):
             section.category = 'fixed'
         elif section.fileid == '32flat' and section not in runtimesections:
diff --git a/src/types.h b/src/types.h
index 097372c..6dd8c43 100644
--- a/src/types.h
+++ b/src/types.h
@@ -70,6 +70,8 @@ extern void __force_link_error__only_in_16bit(void) __noreturn;
 # define VARFSEG __section(".discard.varfseg." UNIQSEC) __VISIBLE __weak
 // Designate a variable at a specific address in the f-segment.
 # define VARFSEGFIXED(addr) __section(".discard.varfixed." UNIQSEC) __VISIBLE __weak
+// Notes a 32bit flat function that must reside in the f-segment.
+# define FUNCFSEG __section(".discard.32fseg." UNIQSEC) __VISIBLE __weak
 // Verify a variable is only accessable via 32bit "init" functions
 # define VARVERIFY32INIT __section(".discard.varinit." UNIQSEC)
 // Designate top-level assembler as 16bit only.
@@ -90,6 +92,7 @@ extern void __force_link_error__only_in_16bit(void) __noreturn;
 # define VARLOW __section(".discard.varlow." UNIQSEC) __VISIBLE __weak
 # define VARFSEG __section(".discard.varfseg." UNIQSEC) __VISIBLE __weak
 # define VARFSEGFIXED(addr) __section(".discard.varfixed." UNIQSEC) __VISIBLE __weak
+# define FUNCFSEG __section(".discard.32fseg." UNIQSEC) __VISIBLE __weak
 # define VARVERIFY32INIT __section(".discard.varinit." UNIQSEC)
 # define ASM16(code)
 # define ASM32FLAT(code)
@@ -106,6 +109,7 @@ extern void __force_link_error__only_in_16bit(void) __noreturn;
 # define VARLOW __section(".data.varlow." UNIQSEC) __VISIBLE __weak
 # define VARFSEG __section(".data.varfseg." UNIQSEC) __VISIBLE
 # define VARFSEGFIXED(addr) __section(".fixedaddr." __stringify(addr)) __VISIBLE __aligned(1)
+# define FUNCFSEG __section(".text.32fseg." UNIQSEC) __VISIBLE
 # define VARVERIFY32INIT __section(".data.varinit." UNIQSEC)
 # define ASM16(code)
 # define ASM32FLAT(code) __ASM(code)
-- 
1.9.3