[SeaBIOS] [PATCH 10/12] Break up call32() into call32() and call32_sloppy()

[Kevin O'Connor]

This separates call32() into two functions.  It also moves the
call16_sloppy() code next to the call32_sloppy() code.

Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
---
 src/stacks.c | 86 +++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 47 insertions(+), 39 deletions(-)

diff --git a/src/stacks.c b/src/stacks.c
index 82d1c5c..2a7be06 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -25,16 +25,12 @@ u16 StackSeg VARLOW;
 u8 Call32Method VARLOW;
 #define C32_SLOPPY 1
 
-// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
-u32 VISIBLE16
-call32(void *func, u32 eax, u32 errret)
+// Call a C function in 32bit mode.  This clobbers the 16bit segment
+// selector registers.
+static u32
+call32_sloppy(void *func, u32 eax)
 {
     ASSERT16();
-    u32 cr0 = getcr0();
-    if (cr0 & CR0_PE)
-        // Called in 16bit protected mode?!
-        return errret;
-
     // Backup cmos index register and disable nmi
     u8 cmosindex = inb(PORT_CMOS_INDEX);
     outb(cmosindex | NMI_DISABLE_BIT, PORT_CMOS_INDEX);
@@ -88,45 +84,65 @@ call32(void *func, u32 eax, u32 errret)
     return eax;
 }
 
-// Call a 16bit SeaBIOS function from a 32bit SeaBIOS function.
+// Jump back to 16bit mode while in 32bit mode from call32_sloppy()
 u32 FUNCFSEG
-call16(u32 eax, u32 edx, void *func)
+call16_sloppy(u32 eax, u32 edx, void *func)
 {
     ASSERT32FLAT();
-    if (getesp() > BUILD_STACK_ADDR)
-        panic("call16 with invalid stack\n");
+    if (getesp() > MAIN_STACK_MAX)
+        panic("call16_sloppy with invalid stack\n");
     func -= BUILD_BIOS_ADDR;
+    Call32Method = 0;
+    u32 stackseg = GET_LOW(StackSeg);
     asm volatile(
         // Transition to 16bit mode
         "  movl $(1f - " __stringify(BUILD_BIOS_ADDR) "), %%edx\n"
-        "  jmp transition16\n"
-        // Call func
+        "  jmp transition16big\n"
+        // Setup ss/esp and call func
         "  .code16\n"
-        "1:movl %2, %%edx\n"
+        "1:movl %3, %%ecx\n"
+        "  shll $4, %3\n"
+        "  movw %%cx, %%ss\n"
+        "  subl %3, %%esp\n"
+        "  movw %%cx, %%ds\n"
+        "  movl %2, %%edx\n"
         "  calll *%1\n"
-        // Return to 32bit
+        // Return to 32bit and restore esp
         "  movl $2f, %%edx\n"
         "  jmp transition32\n"
         "  .code32\n"
-        "2:\n"
+        "2:addl %3, %%esp\n"
         : "+a" (eax)
-        : "r" (func), "r" (edx)
+        : "r" (func), "r" (edx), "r" (stackseg)
         : "edx", "ecx", "cc", "memory");
+    Call32Method = C32_SLOPPY;
     return eax;
 }
 
-// Call a 16bit SeaBIOS function in "big real" mode.
+// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
+u32 VISIBLE16
+call32(void *func, u32 eax, u32 errret)
+{
+    ASSERT16();
+    u32 cr0 = getcr0();
+    if (cr0 & CR0_PE)
+        // Called in 16bit protected mode?!
+        return errret;
+    return call32_sloppy(func, eax);
+}
+
+// Call a 16bit SeaBIOS function from a 32bit SeaBIOS function.
 u32 FUNCFSEG
-call16big(u32 eax, u32 edx, void *func)
+call16(u32 eax, u32 edx, void *func)
 {
     ASSERT32FLAT();
     if (getesp() > BUILD_STACK_ADDR)
-        panic("call16big with invalid stack\n");
+        panic("call16 with invalid stack\n");
     func -= BUILD_BIOS_ADDR;
     asm volatile(
         // Transition to 16bit mode
         "  movl $(1f - " __stringify(BUILD_BIOS_ADDR) "), %%edx\n"
-        "  jmp transition16big\n"
+        "  jmp transition16\n"
         // Call func
         "  .code16\n"
         "1:movl %2, %%edx\n"
@@ -142,38 +158,30 @@ call16big(u32 eax, u32 edx, void *func)
     return eax;
 }
 
-// Jump back to 16bit mode while in 32bit mode from call32()
+// Call a 16bit SeaBIOS function in "big real" mode.
 u32 FUNCFSEG
-call16_sloppy(u32 eax, u32 edx, void *func)
+call16big(u32 eax, u32 edx, void *func)
 {
     ASSERT32FLAT();
-    if (getesp() > MAIN_STACK_MAX)
-        panic("call16_sloppy with invalid stack\n");
+    if (getesp() > BUILD_STACK_ADDR)
+        panic("call16big with invalid stack\n");
     func -= BUILD_BIOS_ADDR;
-    Call32Method = 0;
-    u32 stackseg = GET_LOW(StackSeg);
     asm volatile(
         // Transition to 16bit mode
         "  movl $(1f - " __stringify(BUILD_BIOS_ADDR) "), %%edx\n"
         "  jmp transition16big\n"
-        // Setup ss/esp and call func
+        // Call func
         "  .code16\n"
-        "1:movl %3, %%ecx\n"
-        "  shll $4, %3\n"
-        "  movw %%cx, %%ss\n"
-        "  subl %3, %%esp\n"
-        "  movw %%cx, %%ds\n"
-        "  movl %2, %%edx\n"
+        "1:movl %2, %%edx\n"
         "  calll *%1\n"
-        // Return to 32bit and restore esp
+        // Return to 32bit
         "  movl $2f, %%edx\n"
         "  jmp transition32\n"
         "  .code32\n"
-        "2:addl %3, %%esp\n"
+        "2:\n"
         : "+a" (eax)
-        : "r" (func), "r" (edx), "r" (stackseg)
+        : "r" (func), "r" (edx)
         : "edx", "ecx", "cc", "memory");
-    Call32Method = C32_SLOPPY;
     return eax;
 }
 
-- 
1.9.3