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setup.S: fix for BIOS/DOS not reporting ext mem size

PATCH In review vda 3 participants 4 messages Oct 31, 2001

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#0 lore raw

PATCH 1/1 setup.S: fix for BIOS/DOS not reporting ext mem size

Linus, Alan,

This patch to i386 setup.S resulted from my attempts to load big bzImages from DOS. Loadlin fails at aroung 1020000 bytes, I didn't want to mess with that much asm in loadlin src and wrote new loader from scratch mostly in c.

I had a problem booting from DOS on pc with 196 mb or ram. It turned out int15/e801 and int15/88 reported zero ext mem -> "Less than 4MB" type hang. Digging in loadlin sources turned out some horrors (loadlin hooks itself on int 15/88 and reads CMOS)

I think it's cleaner to do this in setup.S rather than jump thru the hoops in DOS loader. Attached patch does that *only if* int15 methods fail. It does not break existing practice, only adds just another fallback in case of brain damage.

Tested on three boxes. Works for me. Applies cleanly to 2.4.13. If something is wrong with this patch, let me know about it. --
vda

setup.S renamed from setup.S.orig +57 -21
diff -ubB setup.S.orig setup.S
@@ -39,9 +39,13 @@
  * from Ralf Brown interrupt list seem to indicate AX/BX should be used
  * anyway.  So to avoid breaking many machines (presumably there was a reason
  * to orginally use CX/DX instead of AX/BX), we do a kludge to see
- * if CX/DX have been changed in the e801 call and if so use AX/BX .
+ * if CX/DX have been changed in the e801 call and if so use AX/BX.
  * Michael Miller, April 2001 <[email protected]>
  *
+ * Even more fixes for memory detection when started from DOS
+ * TODO: maybe we can just resort to memory scan on our own
+ * to stop using int15/e820,int15/e801,int15/88,cmos once and for all?
+ * <[email protected]> october 2001
  */
 
 #include <linux/config.h>

@@ -297,13 +301,13 @@
 
 #define SMAP  0x534d4150
 
-meme820:
+mem_e820:
 	xorl	%ebx, %ebx			# continuation counter
 	movw	$E820MAP, %di			# point into the whitelist
 						# so we can have the bios
 						# directly write into it.
 
-jmpe820:
+jmp820:
 	movl	$0x0000e820, %eax		# e820, upper word zeroed
 	movl	$SMAP, %edx			# ascii 'SMAP'
 	movl	$20, %ecx			# size of the e820rec

@@ -327,12 +331,10 @@
 	jnl	bail820
 
 	incb	(E820NR)
-	movw	%di, %ax
-	addw	$20, %ax
-	movw	%ax, %di
+	addw	$20, %di
 again820:
-	cmpl	$0, %ebx			# check to see if
-	jne	jmpe820				# %ebx is set to EOF
+	testl	%ebx, %ebx			# check to see if
+	jnz	jmp820				# %ebx is set to EOF
 bail820:
 
 

@@ -344,10 +346,10 @@
 # alternative new memory detection scheme, and it's sensible
 # to write everything into the same place.)
 
-meme801:
+mem_e801:
 	stc					# fix to work around buggy
-	xorw	%cx,%cx				# BIOSes which dont clear/set
-	xorw	%dx,%dx				# carry on pass/error of
+	xorw	%cx, %cx			# BIOSes which dont clear/set
+	xorw	%dx, %dx			# carry on pass/error of
 						# e801h memory size call
 						# or merely pass cx,dx though
 						# without changing them.

@@ -355,28 +357,62 @@
 	int	$0x15
 	jc	mem88
 
-	cmpw	$0x0, %cx			# Kludge to handle BIOSes
-	jne	e801usecxdx			# which report their extended
-	cmpw	$0x0, %dx			# memory in AX/BX rather than
-	jne	e801usecxdx			# CX/DX.  The spec I have read
+	testw	%cx, %cx			# Kludge to handle BIOSes
+	jnz	e801use_cxdx			# which report their extended
+	testw	%dx, %dx			# memory in AX/BX rather than
+	jnz	e801use_cxdx			# CX/DX.  The spec I have read
 	movw	%ax, %cx			# seems to indicate AX/BX
 	movw	%bx, %dx			# are more reasonable anyway...
 
-e801usecxdx:
-	andl	$0xffff, %edx			# clear sign extend
+e801use_cxdx:
+	movzwl	%dx, %edx			# clear sign extend
 	shll	$6, %edx			# and go from 64k to 1k chunks
-	movl	%edx, (0x1e0)			# store extended memory size
-	andl	$0xffff, %ecx			# clear sign extend
- 	addl	%ecx, (0x1e0)			# and add lower memory into
-						# total size.
+	movzwl	%cx, %ecx			# clear sign extend
+	addl	%ecx, %edx			# add lower memory to
+	movl	%edx, (0x1e0)			# extended, store
 
 # Ye Olde Traditional Methode.  Returns the memory size (up to 16mb or
 # 64mb, depending on the bios) in ax.
 mem88:
 
 #endif
+	#stc			# guard against brain damage -
+				#   int 15 must clear cf to indicate success
+	clc			# unbelievable: some BIOSes/DOSes can leave
+				#   cf as is so I had to abandon stc trick
 	movb	$0x88, %ah
 	int	$0x15
+	jc	mem_cmos
+	testw	%ax, %ax
+	jnz	mem_store
+
+# Fallback: if int15/88 fails, get same data from CMOS
+# this works around extremely stupid case I had with PC not booting
+# from DOS when I put 196 megs of RAM in it 
+# (it reported 0 via int15/e801 and int15/88)
+# Also this makes unnecessary for loadlin to jump thru the hoops
+# just in order to let us know ext mem size
+# (it hooks itself on int 15/88 and does CMOS reads for us)
+mem_cmos:
+	pushf			
+	cli
+	movb	$0x18, %al	
+	outb	%al, $0x70
+	#iodelay?		
+	inb	$0x71, %al
+	movb	%al, %ah
+	#iodelay?
+	movb	$0x17, %al
+	outb	%al, $0x70
+	#iodelay?
+	inb	$0x71, %al
+	popf
+	
+mem_store:
+	cmpw	$0xffff-0x400, %ax	# We want to be sure it won't roll over
+	jbe	mem_store2		# 16 bit value when low 1024k gets added
+	movw	$0xffff-0x400, %ax	# thus max memtop is 0xffff*1k = 64m-1k
+mem_store2:
 	movw	%ax, (2)
 
 # Set the keyboard repeat rate to the max
#1 lore raw

Call kernel function from module

Quoted 115 lines · vda

Linus, Alan,

This patch to i386 setup.S resulted from my attempts to load big bzImages from DOS. Loadlin fails at aroung 1020000 bytes, I didn't want to mess with that much asm in loadlin src and wrote new loader from scratch mostly in c.

I had a problem booting from DOS on pc with 196 mb or ram. It turned out int15/e801 and int15/88 reported zero ext mem -> "Less than 4MB" type hang. Digging in loadlin sources turned out some horrors (loadlin hooks itself on int 15/88 and reads CMOS)

I think it's cleaner to do this in setup.S rather than jump thru the hoops in DOS loader. Attached patch does that *only if* int15 methods fail. It does not break existing practice, only adds just another fallback in case of brain damage.

Tested on three boxes. Works for me. Applies cleanly to 2.4.13. If something is wrong with this patch, let me know about it. --
vda

diff -ubB setup.S.orig setup.S

setup.S Wed Oct 31 12:21:45 2001 renamed from setup.S.orig Mon Sep 24 00:58:58 2001 +22 -21
@@ -39,9 +39,13 @@
  * from Ralf Brown interrupt list seem to indicate AX/BX should be used
  * anyway.  So to avoid breaking many machines (presumably there was a reason
  * to orginally use CX/DX instead of AX/BX), we do a kludge to see
- * if CX/DX have been changed in the e801 call and if so use AX/BX .
+ * if CX/DX have been changed in the e801 call and if so use AX/BX.
  * Michael Miller, April 2001 <[email protected]>
  *
+ * Even more fixes for memory detection when started from DOS
+ * TODO: maybe we can just resort to memory scan on our own
+ * to stop using int15/e820,int15/e801,int15/88,cmos once and for all?
+ * <[email protected]> october 2001
  */
 
 #include <linux/config.h>

@@ -297,13 +301,13 @@
 
 #define SMAP  0x534d4150
 
-meme820:
+mem_e820:
        xorl    %ebx, %ebx                      # continuation counter
        movw    $E820MAP, %di                   # point into the whitelist
                                                # so we can have the bios
                                                # directly write into it.
 
-jmpe820:
+jmp820:
        movl    $0x0000e820, %eax               # e820, upper word zeroed
        movl    $SMAP, %edx                     # ascii 'SMAP'
        movl    $20, %ecx                       # size of the e820rec

@@ -327,12 +331,10 @@
        jnl     bail820
 
        incb    (E820NR)
-       movw    %di, %ax
-       addw    $20, %ax
-       movw    %ax, %di
+       addw    $20, %di
 again820:
-       cmpl    $0, %ebx                        # check to see if
-       jne     jmpe820                         # %ebx is set to EOF
+       testl   %ebx, %ebx                      # check to see if
+       jnz     jmp820                          # %ebx is set to EOF
 bail820:
 

@@ -344,10 +346,10 @@
 # alternative new memory detection scheme, and it's sensible
 # to write everything into the same place.)
 
-meme801:
+mem_e801:
        stc                                     # fix to work around buggy
-       xorw    %cx,%cx                         # BIOSes which dont clear/set
-       xorw    %dx,%dx                         # carry on pass/error of
+       xorw    %cx, %cx                        # BIOSes which dont clear/set
+       xorw    %dx, %dx                        # carry on pass/error of
                                                # e801h memory size call
                                                # or merely pass cx,dx though
                                                # without changing them.

@@ -355,28 +357,62 @@
        int     $0x15
        jc      mem88
 
-       cmpw    $0x0, %cx                       # Kludge to handle BIOSes
-       jne     e801usecxdx                     # which report their extended
-       cmpw    $0x0, %dx                       # memory in AX/BX rather than
-       jne     e801usecxdx                     # CX/DX.  The spec I have read
+       testw   %cx, %cx                        # Kludge to handle BIOSes
+       jnz     e801use_cxdx                    # which report their extended
+       testw   %dx, %dx                        # memory in AX/BX rather than
+       jnz     e801use_cxdx                    # CX/DX.  The spec I have read
        movw    %ax, %cx                        # seems to indicate AX/BX
        movw    %bx, %dx                        # are more reasonable anyway...
 
-e801usecxdx:
-       andl    $0xffff, %edx                   # clear sign extend
+e801use_cxdx:
+       movzwl  %dx, %edx                       # clear sign extend
        shll    $6, %edx                        # and go from 64k to 1k chunks
-       movl    %edx, (0x1e0)                   # store extended memory size
-       andl    $0xffff, %ecx                   # clear sign extend
-       addl    %ecx, (0x1e0)                   # and add lower memory into
-                                               # total size.
+       movzwl  %cx, %ecx                       # clear sign extend
+       addl    %ecx, %edx                      # add lower memory to
+       movl    %edx, (0x1e0)                   # extended, store
 
 # Ye Olde Traditional Methode.  Returns the memory size (up to 16mb or

setup.S Wed Oct 31 12:21:45 2001 line 384

Quoted 10 lines
setup.S Wed Oct 31 12:21:45 2001 renamed from setup.S.orig Mon Sep 24 00:58:58 2001 +4 -0
 # 64mb, depending on the bios) in ax.
 mem88:
 
 #endif
+       #stc                    # guard against brain damage -
+                               #   int 15 must clear cf to indicate success
+       clc                     # unbelievable: some BIOSes/DOSes can leave
+                               #   cf as is so I had to abandon stc trick
        movb    $0x88, %ah
        int     $0x15

Hi! Could somebody help me? I added several functions (not sys calls) to kernel as hardcoded part. Then I write modules which will be call these functions. But when I load module insmod says me 'can't resolve symbol my_func_name'.
I exported all my functions in netsyms.c file. Do you know how I can see my function?

Regards,
Niktar.

#2 lore raw

Re: Call kernel function from module

In reply to vda

[snip]

Quoted 7 lines

Hi! Could somebody help me? I added several functions (not sys calls) to kernel as hardcoded part. Then I write modules which will be call these functions. But when I load module insmod says me 'can't resolve symbol my_func_name'.
I exported all my functions in netsyms.c file. Do you know how I can see my function?

use EXPORT_SYMBOL macro from include/module.h

Quoted 8 lines

Regards,
Niktar.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Best regards.

--
Michael Rozhavsky Tel: +972-4-9936248
[email protected] Fax: +972-4-9890564
Optical Access
Senior Software Engineer www.opticalaccess.com

#3 lore raw

Re: Call kernel function from module

In reply to vda
Quoted 11 lines · Michael Rozhavsky

[snip]

Quoted 7 lines

Hi! Could somebody help me? I added several functions (not sys calls) to kernel as hardcoded part. Then I write modules which will be call these functions. But when I load module insmod says me 'can't resolve symbol my_func_name'.
I exported all my functions in netsyms.c file. Do you know how I can see my function?

use EXPORT_SYMBOL macro from include/module.h

Yes. I added it in netsyms.c and I see all my functions in System.map file. (into ksyms too)

#ifdef CONFIG_BATON
#include <linux/baton.h>
EXPORT_SYMBOL(baton_init);
EXPORT_SYMBOL(baton_register_hook);
EXPORT_SYMBOL(baton_unregister_hook);
#endif

Quoted 16 lines
Quoted 9 lines

Regards,
Niktar.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Best regards.

--

   Michael Rozhavsky                    Tel:    +972-4-9936248
   [email protected]         Fax:    +972-4-9890564

Optical Access
Senior Software Engineer www.opticalaccess.com