2008-04-09 05:45:43 a problem about passing global variable between *.c and *.S
sj tian (CHINA)
Message: 53906
I want to pass a global variable "cFlag" from c program to assembly program.and I design a test program. I cleard GPIO_PG1 in c program, and set GPIO_PG1 in assembly program.I pass a value through cFlag to set PORTGIO_SET register in ssembly program.
I define this global variable in c program, and declare it with ".extern _cFlag" in assembly program.Compilation is ok. but when program runing, I found the value of this global variable did not pass into assembly program. after clearing GPIO_PG1 in c program, I can not set GPIO_PG1 in assembly program with cFlag. but if I directly give 0x02 to PORTGIO_SET register, GPIO_PG1 is set 1. I also try to declare this global variable with "cFlag:" in assembly program. but not ok.
I can not find where the problem is. pls give me a hint. The following code is my test progarm.
fpga.h
char cFlag; /* define this global variable*/
extern void Save_Data(); /* declare assembly function*/
fpga_main.c
#include"fpga.h"
.
bfin_write_PORTGIO_DIR(bfin_read_PORTGIO_DIR()|0x07e3);
static int fpga_ioctl(struct inode * inode,struct file * filp,unsigned int cmd,unsigned long arg)
{
.
case fpga_IOC_SET_PG1:
gpio_set_value(GPIO_PG1,0); /*clear GPIO_PG1*/
Temp = bfin_read_PORTGIO_SET();
printk("nTemp1 %d \n",Temp);
cFlag = 0x02;
Save_Data(); /*assembly function will set GPIO_GP1 1*/
Temp = bfin_read_PORTGIO_SET();
printk("nTemp %d \n",Temp);
break;
.
}
isr.S
.extern _cFlag; /* declare this global variable*/
//cFlag:
//.long 0;
.text;
.global _Save_Data;
.align 4;
_Save_Data:
//[--sp] = rets;
//[--sp] = astat;
//r4.l = 0x02;
r4.l = _cFlag;
p0.l = 0x1508; /*address of PORTGIO_SET register* /
p0.h = 0xFFC0;
w[p0] = r4.l; /*SET GPIO_PG1 1*/
//astat = [sp++];
//rets = [sp++];
//_Save_Data_end:
rts;
//_Save_Data.END:
makefile
obj-m := fpga.o
fpga-objs :=fpga_main.o isr.o
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2008-04-09 12:20:44 Re: a problem about passing global variable between *.c and *.S
Mike Frysinger (UNITED STATES)
Message: 53937 you arent dereferencing the variable properly. why are you doing argument passing that way anyways ? just use the normal C ABI and pass things via registers. actually, why are you writing assembly at all ? everything you're doing can be done in C.
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2008-04-09 21:43:51 Re: a problem about passing global variable between *.c and *.S
sj tian (CHINA)
Message: 53951
Thanks for your reply!
This is only a test program. I am transplanting a program under visual dsp++ to uClinux. and this program under visual dsp included *.c and *.s.this *.s is optimized and can satisfy our time request. I can not rewrite it in c language. *.s file used sevaral global variables defined in *.c. when transplanting, I found I can not passing properly the value of the global variable from *.c to *.s. so I write this test progarm to try how to pass proberly the value of the global variable. I have been working on this for servel days and I am out of ideas now.
If I want to passing proberly the value of the global variable from *.c to *.s, how do I use this global variable in *.s ans how to define it in *.c.
Thanks!
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2008-04-09 22:52:34 Re: a problem about passing global variable between *.c and *.S
Mike Frysinger (UNITED STATES)
Message: 53954 if passing the value as an argument isnt working, you're probably not doing it right ... but in the end, the answer is the same as last time you asked the same question.
read the documentation:
http://sourceware.org/binutils/docs-2.18/as/index.html
http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
or just write the code in C and see what gcc does:
bfin-uclinux-gcc test.c -S -o -
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2008-04-10 21:45:20 Re: a problem about passing global variable between *.c and *.S
sj tian (CHINA)
Message: 54057
Thanks！
I have sovled this problem.
But there is another problem, after runing some time, there is some exceptional in my assembly program.
I copy some exceptional information, but I don't know what information it tell me.
Undefined instruction
- May be used to emulate instructions that are not defined for
a particular processor implementation.
CURRENT PROCESS:
COMM=myprog PID=43
TEXT = 0x01020040-0x0102fda0 DATA = 0x0102fda4-0x01036464
BSS = 0x01036464-0x0103bed4 USER-STACK = 0x0103ff80
return address: 0x010253b8; contents of [PC-16...PC+8]:
0000 0000 0000 0000 0000 0000 0000 0000
0000 0000 0000 0000 0000 0000 0000 0000 X
e1c2 3a14 163a c6e5 d1c7 cad3 e4ca 3610
RETE: 00000000 RETN: 003da000 RETX: 010253b8 RETS: 01022a84
IPEND: 0030 SYSCFG: 0036
SEQSTAT: 00000021 SP: 003d9f24
R0: 00000000 R1: 00000001 R2: 00000003 R3: 00000001
R4: 0103b2e0 R5: 0103bc70 R6: 0103b306 R7: 000f060f
P0: 0103b2e0 P1: 01038ca6 P2: 000f060f P3: 0103bc42
P4: 01039890 P5: 01038cb0 FP: 003d3d10
A0.w: 00000000 A0.x: 00000000 A1.w: 00000000 A1.x: 00000000
LB0: 0102914d LT0: 0102914a LC0: 00000000
LB1: 014af2c9 LT1: 014af2c8 LC1: 00000000
B0: 00000000 L0: 00000000 M0: 00000000 I0: 00000004
B1: 00000000 L1: 00000000 M1: 00000000 I1: 00000000
B2: 00000000 L2: 00000000 M2: 00000000 I2: 00000000
B3: 00000000 L3: 00000000 M3: 00000000 I3: 00000000
USP: 003d3d04 ASTAT: 02003004
DCPLB_FAULT_ADDR=003d9ffc
ICPLB_FAULT_ADDR=010253b8
Hardware Trace:
0 Target : [<0x00004480>]
Source : [<0xffa00ae0>]
1 Target : [<0xffa00a2c>]
Source : [<0xffa00a2a>]
2 Target : [<0xffa009dc>]
Source : [<0xffa00b80>]
3 Target : [<0xffa00b58>]
Source : <0x010253b6> [ myprog + 0x5376 ]
4 Target : <0x01022432> [ myprog + 0x23f2 ]
Source : [<0xffa010e6>]
5 Target : [<0xffa01084>]
Source : [<0xffa00d08>]
6 Target : [<0xffa00d04>]
Source : [<0xffa00cf4>]
7 Target : [<0xffa00cee>]
Source : [<0xffa00cde>]
8 Target : [<0xffa00ccc>]
Source : [<0xffa00cec>]
9 Target : [<0xffa00cea>]
Source : [<0xffa018b6>]
10 Target : [<0xffa0189e>]
Source : [<0xffa01884>]
11 Target : [<0xffa01864>]
Source : [<0xffa00d82>]
12 Target : [<0xffa00d7c>]
Source : [<0xffa00d7a>]
13 Target : [<0xffa00d4c>]
Source : [<0xffa01860>]
14 Target : [<0xffa0185c>]
Source : [<0xffa01dc0>]
15 Target : [<0xffa01da4>]
Source : [<0xffa01d9c>]
Stack from 003d9f04:
0103bc42 ffa00ae4 0011670c 0011670c 00116708 00000001 0103b2e0 00202080
010253b8 00000030 00000021 00000000 003da000 010253b8 010253b8 01022a84
00000000 02003004 014af2c9 0102914d 014af2c8 0102914a 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000004 003d3d04 003d3d10 01038cb0 01039890
Call Trace:[<000f060f>][<000f060f>]
I did not use emulate instructions .
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2008-04-10 22:14:37 Re: a problem about passing global variable between *.c and *.S
Mike Frysinger (UNITED STATES)
Message: 54060 please review the documentation:
http://docs.blackfin.uclinux.org/doku.php?id=debuging_applications#analyzing_traces