[PATCH 1/2] Move a20 code from system.c and ps2port.h to x86.h

[Kevin O'Connor]

Although the a20 functionality was originally implemented in the ps2
controller, that is just a historical artifact.  It's a core feature
of modern x86 cpus and the code is better located in the x86.h header.

Signed-off-by: Kevin O'Connor <[e-mail]>
---
 src/hw/ps2port.h | 14 +++-----------
 src/romlayout.S  |  1 -
 src/system.c     | 20 ++------------------
 src/x86.h        | 15 ++++++++++++++-
 4 files changed, 19 insertions(+), 31 deletions(-)

diff --git a/src/hw/ps2port.h b/src/hw/ps2port.h
index 2e6f25a..566073a 100644
--- a/src/hw/ps2port.h
+++ b/src/hw/ps2port.h
@@ -2,13 +2,11 @@
 #ifndef __PS2PORT_H
 #define __PS2PORT_H
 
+#include "types.h" // u8
+
 #define PORT_PS2_DATA          0x0060
 #define PORT_PS2_CTRLB         0x0061
 #define PORT_PS2_STATUS        0x0064
-#define PORT_A20               0x0092
-
-// PORT_A20 bitdefs
-#define A20_ENABLE_BIT 0x02
 
 // Standard commands.
 #define I8042_CMD_CTL_RCTR      0x0120
@@ -60,16 +58,10 @@
 #define I8042_CTR_AUXDIS        0x20
 #define I8042_CTR_XLATE         0x40
 
-#ifndef __ASSEMBLY__
-
-#include "types.h" // u8
-
-// functions
+// ps2port.c
 void i8042_reboot(void);
 int ps2_kbd_command(int command, u8 *param);
 int ps2_mouse_command(int command, u8 *param);
 void ps2port_setup(void);
 
-#endif // !__ASSEMBLY__
-
 #endif // ps2port.h
diff --git a/src/romlayout.S b/src/romlayout.S
index 0651112..cca4e43 100644
--- a/src/romlayout.S
+++ b/src/romlayout.S
@@ -8,7 +8,6 @@
 #include "asm-offsets.h" // BREGS_*
 #include "config.h" // CONFIG_*
 #include "entryfuncs.S" // ENTRY_*
-#include "hw/ps2port.h" // PORT_A20
 #include "hw/rtc.h" // CMOS_RESET_CODE
 #include "x86.h" // CR0_*
 
diff --git a/src/system.c b/src/system.c
index 756dc31..bcf7e90 100644
--- a/src/system.c
+++ b/src/system.c
@@ -8,28 +8,12 @@
 #include "biosvar.h" // GET_GLOBAL
 #include "bregs.h" // struct bregs
 #include "hw/pic.h" // pic_reset
-#include "hw/ps2port.h" // PORT_A20
 #include "malloc.h" // LegacyRamSize
 #include "memmap.h" // E820_RAM
 #include "output.h" // debug_enter
 #include "string.h" // memcpy_far
 #include "util.h" // handle_1553
-#include "x86.h" // inb
-
-// Use PS2 System Control port A to set A20 enable
-static inline u8
-set_a20(u8 cond)
-{
-    // get current setting first
-    u8 newval, oldval = inb(PORT_A20);
-    if (cond)
-        newval = oldval | A20_ENABLE_BIT;
-    else
-        newval = oldval & ~A20_ENABLE_BIT;
-    outb(newval, PORT_A20);
-
-    return (oldval & A20_ENABLE_BIT) != 0;
-}
+#include "x86.h" // set_a20
 
 static void
 handle_152400(struct bregs *regs)
@@ -48,7 +32,7 @@ handle_152401(struct bregs *regs)
 static void
 handle_152402(struct bregs *regs)
 {
-    regs->al = (inb(PORT_A20) & A20_ENABLE_BIT) != 0;
+    regs->al = get_a20();
     set_code_success(regs);
 }
 
diff --git a/src/x86.h b/src/x86.h
index 65f42b3..57773d2 100644
--- a/src/x86.h
+++ b/src/x86.h
@@ -14,6 +14,10 @@
 #define CR0_NW (1<<29) // Not Write-through
 #define CR0_PE (1<<0)  // Protection enable
 
+// PORT_A20 bitdefs
+#define PORT_A20 0x0092
+#define A20_ENABLE_BIT 0x02
+
 #ifndef __ASSEMBLY__
 
 #include "types.h" // u32
@@ -216,10 +220,19 @@ static inline void lgdt(struct descloc_s *desc) {
     asm("lgdtl %0" : : "m"(*desc) : "memory");
 }
 
+static inline u8 get_a20(void) {
+    return (inb(PORT_A20) & A20_ENABLE_BIT) != 0;
+}
+
+static inline u8 set_a20(u8 cond) {
+    u8 val = inb(PORT_A20);
+    outb((val & ~A20_ENABLE_BIT) | (cond ? A20_ENABLE_BIT : 0), PORT_A20);
+    return (val & A20_ENABLE_BIT) != 0;
+}
+
 // x86.c
 void cpuid(u32 index, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
 
-
 #endif // !__ASSEMBLY__
 
 #endif // x86.h
-- 
1.9.3

[PATCH 2/2] Backup and restore a20 on call32_sloppy()

[Kevin O'Connor]

Previously, the a20 line would always be enabled and left on after
call32_sloppy().  The setting should really be backed up and restored
on each call.

Signed-off-by: Kevin O'Connor <[e-mail]>
---
 src/stacks.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/stacks.c b/src/stacks.c
index 0d3eb77..b8d6e62 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -25,6 +25,7 @@
 struct {
     u8 method;
     u8 cmosindex;
+    u8 a20;
     u16 ss, fs, gs;
     struct descloc_s gdt;
 } Call32Data VARLOW;
@@ -174,6 +175,9 @@ call32_sloppy_prep(void)
     inb(PORT_CMOS_DATA);
     SET_LOW(Call32Data.cmosindex, cmosindex);
 
+    // Enable a20 and backup it's previous state
+    SET_LOW(Call32Data.a20, set_a20(1));
+
     // Backup ss/fs/gs and gdt
     SET_LOW(Call32Data.ss, GET_SEG(SS));
     SET_LOW(Call32Data.fs, GET_SEG(FS));
@@ -201,6 +205,9 @@ call32_sloppy_post(void)
     SET_SEG(FS, GET_LOW(Call32Data.fs));
     SET_SEG(GS, GET_LOW(Call32Data.gs));
 
+    // Restore a20
+    set_a20(GET_LOW(Call32Data.a20));
+
     // Restore cmos index register
     outb(GET_LOW(Call32Data.cmosindex), PORT_CMOS_INDEX);
     inb(PORT_CMOS_DATA);
-- 
1.9.3