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SubjectCall kernel function from module
vda wrote:
>
> 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.orig Mon Sep 24 00:58:58 2001
> +++ setup.S Wed Oct 31 12:21:45 2001
> @@ -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 <michaelm@mjmm.org>
> *
> + * 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?
> + * <vda@port.imtp.ilyichevsk.odessa.ua> 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

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.
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