[SeaBIOS] [RFC] [PATCH 1/2] Implement support for transitioning from 16 bit to 32 bit
Kevin O'Connor
kevin at koconnor.net
Tue Nov 23 02:13:34 CET 2010
On Mon, Nov 22, 2010 at 07:40:36PM -0500, Kevin O'Connor wrote:
> It should be possible to extend call32() to do what you need -
FYI - here's what call32 extended to pass a parameter looks like:
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -37,14 +37,14 @@ static inline void lgdt(struct descloc_s *desc) {
}
// Call a 32bit SeaBIOS function from a 16bit SeaBIOS function.
-static inline int
-call32(void *func)
+static inline u32
+call32(void *func, u32 eax, u32 errret)
{
ASSERT16();
u32 cr0 = getcr0();
if (cr0 & CR0_PE)
// Called in 16bit protected mode?!
- return -1;
+ return errret;
// Backup cmos index register and disable nmi
u8 cmosindex = inb(PORT_CMOS_INDEX);
@@ -69,7 +69,7 @@ call32(void *func)
" pushl $(" __stringify(BUILD_BIOS_ADDR) " + 1f)\n"
" jmp transition32\n"
" .code32\n"
- "1:calll *%2\n"
+ "1:calll *%3\n"
" pushl $2f\n"
" jmp transition16big\n"
@@ -78,9 +78,9 @@ call32(void *func)
"2:movl %0, %%ds\n"
" movl %0, %%ss\n"
" movl %1, %%esp\n"
- : "=&r" (bkup_ss), "=&r" (bkup_esp)
+ : "=&r" (bkup_ss), "=&r" (bkup_esp), "+a" (eax)
: "r" (func)
- : "eax", "ecx", "edx", "cc", "memory");
+ : "ecx", "edx", "cc", "memory");
// Restore gdt and fs/gs
lgdt(&gdt);
@@ -90,7 +90,7 @@ call32(void *func)
// Restore cmos index register
outb(cmosindex, PORT_CMOS_INDEX);
inb(PORT_CMOS_DATA);
- return 0;
+ return eax;
}
// 16bit trampoline for enabling irqs from 32bit mode.
@@ -393,5 +393,5 @@ check_preempt(void)
|| GET_FLATPTR(MainThread.next) == &MainThread)
return;
- call32(yield_preempt);
+ call32(yield_preempt, 0, 0);
}
-Kevin
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