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List: grub-devel
Subject: [PATCH] Proof of concept interrupt wrapping
From: Vladimir ' <phcoder () gmail !
Date: 2009-12-31 12:28:30
Message-ID: 4B3C98EE.8020003 () gmail ! com
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Hello. We were discussing with Robert how to move BIOS interrupt
routines out of kernel. There are following possibilities:
1) Have a .lowmem section in every concerned module which will always be
placed in low memory. Currently in experimental.
Advantages:
a) moving functions to modules is straightforward
b) functions grow neither in size nor in complexity
Disadvantages:
c) needs lowmem allocators in core
2) Make every function needing bios interrupts setup its own trampoline.
Due to complexity of trampolines it's not a real option
3) Have an universal routine grub_interrupt (int intno, struct
grub_cpu_interrupt_regs *regs) which will be used by C routine to do the
interrupt calls. This would move the complexity from asm to C.
Advantages:
a) simplicity in core
b) complexity moved to a more readable language
c) we can also rename grub_interrupt to grub_interrupt_real and make
grub_interrupt dprintf registers before and after the call. This would
make debugging BIOS quirks easier.
Disadvantages:
a) Moving functions needs effort
b) C functions are probably bigger but it may be offset by possibility
of inlining functions
c) repeadetly changing from/to real mode is an overhead when executing
multiple interrupts in series. Fortunately this condition is rare in our
codebase and is only on non performance-critical parts like halting.
d) Some functions aren't covered by this. At least grub_pxe_call is in
this case. But we can use method 2 for them
--
Regards
Vladimir 'φ-coder/phcoder' Serbinenko
["intwrap.diff" (text/x-diff)]
=== modified file 'conf/i386-pc.rmk'
--- conf/i386-pc.rmk 2009-12-25 22:06:52 +0000
+++ conf/i386-pc.rmk 2009-12-31 12:07:51 +0000
@@ -64,7 +64,7 @@
partition.h msdos_partition.h reader.h symbol.h term.h time.h types.h \
machine/biosdisk.h machine/boot.h machine/console.h machine/init.h \
machine/memory.h machine/loader.h machine/vga.h machine/vbe.h \
- machine/kernel.h machine/pxe.h i386/pit.h list.h handler.h command.h i18n.h
+ machine/kernel.h machine/pxe.h i386/pit.h list.h handler.h command.h i18n.h \
machine/int.h kernel_img_CFLAGS = $(COMMON_CFLAGS) $(TARGET_IMG_CFLAGS)
kernel_img_ASFLAGS = $(COMMON_ASFLAGS)
kernel_img_LDFLAGS = $(COMMON_LDFLAGS) \
$(TARGET_IMG_LDFLAGS)$(GRUB_KERNEL_MACHINE_LINK_ADDR) $(COMMON_CFLAGS)
=== modified file 'disk/i386/pc/biosdisk.c'
--- disk/i386/pc/biosdisk.c 2009-12-10 18:15:20 +0000
+++ disk/i386/pc/biosdisk.c 2009-12-31 12:07:51 +0000
@@ -19,6 +19,7 @@
#include <grub/machine/biosdisk.h>
#include <grub/machine/memory.h>
#include <grub/machine/kernel.h>
+#include <grub/machine/int.h>
#include <grub/disk.h>
#include <grub/dl.h>
#include <grub/mm.h>
@@ -28,6 +29,59 @@
#include <grub/term.h>
static int cd_drive = 0;
+static int grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap);
+
+static int grub_biosdisk_get_num_floppies (void)
+{
+ struct grub_cpu_int_registers regs;
+ int drive;
+
+ /* reset the disk system first */
+ regs.ax = 0;
+ regs.dx = 0;
+ regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
+
+ grub_cpu_interrupt (0x13, ®s);
+
+ for (drive = 0; drive < 2; drive++)
+ {
+ regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT | GRUB_CPU_INT_FLAGS_CARRY;
+ regs.dx = drive;
+
+ /* call GET DISK TYPE */
+ regs.ax = 0x1500;
+ grub_cpu_interrupt (0x13, ®s);
+ if (regs.flags & GRUB_CPU_INT_FLAGS_CARRY)
+ break;
+
+ /* check if this drive exists */
+ if (!(regs.ax & 0x300))
+ break;
+ }
+
+ return drive;
+}
+
+/*
+ * Call IBM/MS INT13 Extensions (int 13 %ah=AH) for DRIVE. DAP
+ * is passed for disk address packet. If an error occurs, return
+ * non-zero, otherwise zero.
+ */
+
+static int
+grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap)
+{
+ struct grub_cpu_int_registers regs;
+ regs.ax = ah << 8;
+ /* compute the address of disk_address_packet */
+ regs.ds = (((grub_addr_t) dap) & 0xffff0000) >> 4;
+ regs.si = (((grub_addr_t) dap) & 0xffff);
+ regs.dx = drive;
+ regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
+
+ grub_cpu_interrupt (0x13, ®s);
+ return regs.ax >> 8;
+}
static int
grub_biosdisk_get_drive (const char *name)
=== modified file 'include/grub/i386/pc/biosdisk.h'
--- include/grub/i386/pc/biosdisk.h 2009-06-10 21:04:23 +0000
+++ include/grub/i386/pc/biosdisk.h 2009-12-31 12:07:51 +0000
@@ -106,7 +106,6 @@
grub_uint64_t block;
} __attribute__ ((packed));
-int EXPORT_FUNC(grub_biosdisk_rw_int13_extensions) (int ah, int drive, void *dap);
int EXPORT_FUNC(grub_biosdisk_rw_standard) (int ah, int drive, int coff, int hoff,
int soff, int nsec, int segment);
int EXPORT_FUNC(grub_biosdisk_check_int13_extensions) (int drive);
@@ -118,7 +117,6 @@
unsigned long *cylinders,
unsigned long *heads,
unsigned long *sectors);
-int EXPORT_FUNC(grub_biosdisk_get_num_floppies) (void);
void grub_biosdisk_init (void);
void grub_biosdisk_fini (void);
=== added file 'include/grub/i386/pc/int.h'
--- include/grub/i386/pc/int.h 1970-01-01 00:00:00 +0000
+++ include/grub/i386/pc/int.h 2009-12-31 12:07:51 +0000
@@ -0,0 +1,50 @@
+/*
+ * GRUB -- GRand Unified Bootloader
+ * Copyright (C) 2009 Free Software Foundation, Inc.
+ *
+ * GRUB is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GRUB is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef GRUB_INTERRUPT_MACHINE_HEADER
+#define GRUB_INTERRUPT_MACHINE_HEADER 1
+
+#include <grub/symbol.h>
+
+struct grub_cpu_int_registers
+{
+ grub_uint16_t bx;
+ grub_uint16_t es;
+ grub_uint16_t cx;
+ grub_uint16_t ax;
+ grub_uint16_t dx;
+ grub_uint16_t ds;
+ grub_uint16_t di;
+ grub_uint16_t flags;
+ grub_uint16_t si;
+};
+
+#define GRUB_CPU_INT_FLAGS_CARRY 0x1
+#define GRUB_CPU_INT_FLAGS_PARITY 0x4
+#define GRUB_CPU_INT_FLAGS_ADJUST 0x10
+#define GRUB_CPU_INT_FLAGS_ZERO 0x40
+#define GRUB_CPU_INT_FLAGS_SIGN 0x80
+#define GRUB_CPU_INT_FLAGS_TRAP 0x100
+#define GRUB_CPU_INT_FLAGS_INTERRUPT 0x200
+#define GRUB_CPU_INT_FLAGS_DIRECTION 0x400
+#define GRUB_CPU_INT_FLAGS_OVERFLOW 0x800
+#define GRUB_CPU_INT_FLAGS_DEFAULT GRUB_CPU_INT_FLAGS_INTERRUPT
+
+void EXPORT_FUNC (grub_cpu_interrupt) (grub_uint8_t intno, struct \
grub_cpu_int_registers *regs); +
+#endif
=== modified file 'kern/i386/pc/startup.S'
--- kern/i386/pc/startup.S 2009-12-25 22:01:32 +0000
+++ kern/i386/pc/startup.S 2009-12-31 12:07:51 +0000
@@ -567,44 +567,6 @@
#include "../loader.S"
/*
- * int grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap)
- *
- * Call IBM/MS INT13 Extensions (int 13 %ah=AH) for DRIVE. DAP
- * is passed for disk address packet. If an error occurs, return
- * non-zero, otherwise zero.
- */
-
-FUNCTION(grub_biosdisk_rw_int13_extensions)
- pushl %ebp
- pushl %esi
-
- /* compute the address of disk_address_packet */
- movw %cx, %si
- xorw %cx, %cx
- shrl $4, %ecx /* save the segment to cx */
-
- /* ah */
- movb %al, %dh
- /* enter real mode */
- call prot_to_real
-
- .code16
- movb %dh, %ah
- movw %cx, %ds
- int $0x13 /* do the operation */
- movb %ah, %dl /* save return value */
- /* back to protected mode */
- DATA32 call real_to_prot
- .code32
-
- movb %dl, %al /* return value in %eax */
-
- popl %esi
- popl %ebp
-
- ret
-
-/*
* int grub_biosdisk_rw_standard (int ah, int drive, int coff, int hoff,
* int soff, int nsec, int segment)
*
@@ -862,43 +824,6 @@
/*
- * int grub_biosdisk_get_num_floppies (void)
- */
-FUNCTION(grub_biosdisk_get_num_floppies)
- pushl %ebp
-
- xorl %edx, %edx
- call prot_to_real
-
- .code16
- /* reset the disk system first */
- int $0x13
-1:
- stc
-
- /* call GET DISK TYPE */
- movb $0x15, %ah
- int $0x13
-
- jc 2f
-
- /* check if this drive exists */
- testb $0x3, %ah
- jz 2f
-
- incb %dl
- cmpb $2, %dl
- jne 1b
-2:
- DATA32 call real_to_prot
- .code32
-
- movl %edx, %eax
- popl %ebp
- ret
-
-
-/*
*
* grub_get_memsize(i) : return the memory size in KB. i == 0 for conventional
* memory, i == 1 for extended memory
@@ -2142,3 +2067,74 @@
popl %esi
popl %ebp
ret
+
+FUNCTION(grub_cpu_interrupt)
+ pushl %ebp
+ pushl %esi
+ pushl %edi
+ pushl %ebx
+ pushl %edx
+ movb %al, intno
+ movl %edx, %esi
+
+ movl 0(%esi), %ebx
+ movl 4(%esi), %ecx
+ movl 8(%esi), %edx
+ movl 12(%esi), %edi
+ movw 16(%esi), %si
+
+ call prot_to_real
+ .code16
+ movl %edi, %eax
+ shrl $16, %eax
+ push %ax
+
+ movl %ebx, %eax
+ shrl $16, %eax
+ movw %ax, %es
+
+ movl %edx, %eax
+ shrl $16, %eax
+ movw %ax, %ds
+
+ movl %ecx, %eax
+ shrl $16, %eax
+
+ popf
+ .byte 0xcd
+intno:
+ .byte 0
+
+ pushf
+ andl $0xffff, %ebx
+ andl $0xffff, %ecx
+ andl $0xffff, %edx
+ andl $0xffff, %edi
+
+ shll $16, %eax
+ orl %eax, %ecx
+
+ movw %ds, %ax
+ shll $16, %eax
+ orl %eax, %edx
+
+ pop %ax
+ shll $16, %eax
+ orl %eax, %edi
+
+ DATA32 call real_to_prot
+ .code32
+ pushl %esi
+ movl 4(%esp), %esi
+ movl %ebx, 0(%esi)
+ movl %ecx, 4(%esi)
+ movl %edx, 8(%esi)
+ movl %edi, 12(%esi)
+ popl %eax
+ movw %ax, 16(%esi)
+ popl %eax
+ popl %ebx
+ popl %edi
+ popl %esi
+ popl %ebp
+ ret
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