vecttbl

MIPS处理器的bootloader,龙芯就是用的修改过的PMON2

		PMON Vector Table
		PMON Vector Table

The vector table allows a client program to access a number of
target-dependent services provided by the PROM Monitor. The linkage
mechanism for all these services is to jump to an address obtained from
the vector table. For example,

		li	t0,TBLBASE
		lw	t0,OFFSET(t0)
		j	t0

Where TBLBASE is 0xa0c00200 for the ATMizer-I, and
0xbfc00200 for all other processors. OFFSET is obtained from 
the table below.

The following table shows the services that are
provided, the arguments that are passed to each service function, and
the table offset for each service. The declaration for vector table itself 
is located
in the file pmon/mips.s. Normally an
application establishes a connection to these services by linking
in the file lib/crt1.s. This routine
is automatically linked with your application when you use the
pmcc command.

PROM Monitor Vector Table
OffsetFunctionUsage

0

read(int fd, char *buf, int size)

Read specified number of bytes into buf. Returns number of
bytes read.

4

write(int fd, char *buf, int size)

Write specified number of bytes from buf. Returns number of
bytes written.

8

int open(char *name [,int mode])

Open a device. Returns file descriptor.

12

close(int fd)

Close a file descriptor.

16

ioctl(int fd, int request, arg)

Perform I/O control operation.

20

printf(char *fmtstr, arg...)

Print formatted to stdout.

24

vsprintf(char *dst, char *fmtstr, arglist)

Write formatted string to dst using arglist. used by printf.

28

ttctl(int fd, int op, arg...)

Perform terminal specific operations.

32

exit(int status)

Client exit to PMON.

36

char *getenv(char *name)

Return a pointer to the value of the named environment variable. Return
zero if not found.

40

onintr(int code, long *dat)

Connect interrupt handler to specified exception code. 

44

flush_cache(ICACHE|DCACHE)

Flush the selected cache.

48

_exception()

Transfer control to PMON's exception handler.

52

_fpstatesz()

Return size of fp state. Requires fp emulation.

56

_fpinit()

Initialize the fp emulation package. Standard fp emulation only.

60

_fpstate()

Return pointer to fp state. Requires fp emulation.

64

cop1()

Transfer control to PMON's exception handler for fp exceptions.
Requires fp emulation.

68

adr2symoff(char *dst, int value, int width)

Convert addr to symbol+offset. Return zero if not found.

72

sym2adr(long *v, char *label)

Find the value of a label. Return zero if not found.

76

getclkfreq()

Return the CPU clock frequency (in MHz)

80

_clkinit()

Initialize the clock. Required before getclkfreq().