NAME
cisctrace, risctrace, ciscframe, riscframe, localaddr, symoff, fpformat, beieee80ftos, beieeesftos, beieeedftos, leieee80ftos, leieeesftos, leieeedftos, ieeesftos, ieeedftos – machine–independent debugger functions

SYNOPSIS
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <mach.h>

int cisctrace(Map *map, ulong pc, ulong sp, ulong link,
Tracer trace)

int risctrace(Map *map, ulong pc, ulong sp, ulong link,
Tracer trace)

ulong ciscframe(Map *map, ulong addr, ulong pc, ulong sp,
ulong link)

ulong riscframe(Map *map, ulong addr, ulong pc, ulong sp,
ulong link)

int localaddr(Map *map, char *fn, char *var, long *ret,
Rgetter rget)

int symoff(char *buf, int n, long addr, int type)

int fpformat(Map *map, Reglist *rp, char *buf, int n, int code)

int beieee80ftos(char *buf, int n, void *fp)

int beieeesftos(char *buf, int n, void *fp)

int beieeedftos(char *buf, int n, void *fp)

int leieee80ftos(char *buf, int n, void *fp)

int leieeesftos(char *buf, int n, void *fp)

int leieeedftos(char *buf, int n, void *fp)

int ieeesftos(char *buf, int n, ulong f)

int ieeedftos(char *buf, int n, ulong high, ulong low)

extern Machdata *machdata;

DESCRIPTION
These functions provide machine–independent implementations of common debugger functions. Many of the functions assume that global variables mach and machdata point to the Mach and Machdata data structures describing the target architecture. The former contains machine parameters and a description of the register set; it is usually set by invoking crackhdr (see mach(2)) to interpret the header of an executable. The Machdata structure is primarily a jump table specifying functions appropriate for processing an executable image for a given architecture. Each application is responsible for setting machdata to the address of the Machdata structure for the target architecture. Many of the functions described here are not called directly; instead, they are invoked indirectly through the Machdata jump table.

These functions must retrieve data and register contents from an executing image. The Map (see mach(2)) data structure supports the consistent retrieval of data, but no uniform access mechanism exists for registers. The application passes the address of a register retrieval function as an argument to those functions requiring register values. This function, called an Rgetter, is of the form

ulong rget(Map *map, char *name);

It returns the contents of a register when given the address of a Map associated with an executing image and the name of the register.

Cisctrace and risctrace unwind the stack for up to 40 levels or until the frame for main is found. They return the count of the number of levels unwound. These functions process stacks conforming to the generic compiler model for RISC and CISC architectures, respectively. Map is the address of a Map data structure associated with the image of an executing process. Sp, pc and link are starting values for the stack pointer, program counter, and link register from which the unwinding is to take place. Normally, they are the current contents of the appropriate registers but they can be any values defining a legitimate process context, for example, an alternate stack in a multi–threaded process. Trace is the address of an application–supplied function to be called on each iteration as the frame unwinds. The prototype of this function is:

void tracer(Map *map, ulong pc, ulong fp, Symbol *s);

where Map is the Map pointer passed to cisctrace or risctrace and pc and fp are the program counter and frame pointer. S is the address of a Symbol structure, as defined in symbol(2), containing the symbol table information for the function owning the frame (i.e., the function that caused the frame to be instantiated).

Ciscframe and riscframe calculate the frame pointer associated with a function. They are suitable for programs conforming to the CISC and RISC stack models. Map is the address of a Map associated with the memory image of an executing process. Addr is the entry point of the desired function. Pc, sp and link are the program counter, stack pointer and link register of an execution context. As with the stack trace functions, these can be the current values of the registers or any legitimate execution context. The value of the frame pointer is returned. A return value of zero indicates an error.

Localaddr fills the location pointed to by ret with the address of a local variable. Map is the address of a Map associated with an executing memory image. Fn and var are pointers to the names of the function and variable of interest. Rget is the address of a register retrieval function. If both fn and var are non–zero, the frame for function fn is calculated and the address of the automatic or argument named var in that frame is returned. If var is zero, the address of the frame for function fn is returned. In all cases, the frame for the function named fn must be instantiated somewhere on the current stack. If there are multiple frames for the function (that is, if it is recursive), the most recent frame is used. The search starts from the context defined by the current value of the program counter and stack pointer. If a valid address is found, localaddr returns 1. A negative return indicates an error in resolving the address.

Symoff converts a virtual address to a symbolic reference. The string containing that reference is of the form `name+offset', where `name' is the name of the nearest symbol with an address less than or equal to the target address and `offset' is the hexadecimal offset beyond that symbol. If `offset' is zero, only the name of the symbol is printed. If no symbol is found within 4,096 bytes of the address, the address is formatted as a hexadecimal address. Buf is the address of a buffer of n characters to receive the formatted string. Addr is the address to be converted. Type is the type code of the search space: CTEXT, CDATA, or CANY. Symoff returns the length of the formatted string contained in buf.

Fpformat converts the contents of a floating point register to a string. Map is the address of a Map associated with an executing process. Rp is the address of a Reglist data structure describing the desired register. Buf is the address of a buffer of n characters to hold the resulting string. Code must be either F or f, selecting double or single precision, respectively. If code is F, the contents of the specified register and the following register are interpreted as a double precision floating point number; this is only meaningful for architectures that implement double precision floats by combining adjacent single precision registers. For code f, the specified register is formatted as a single precision float. Fpformat returns 1 if the number is successfully converted or –1 in the case of an error.

Beieee80ftos, beieeesftos and beieeedftos convert big–endian 80–bit extended, 32–bit single precision, and 64–bit double precision floating point values to a string. Leieee80ftos, leieeesftos, and leieeedftos are the little–endian counterparts. Buf is the address of a buffer of n characters to receive the formatted string. Fp is the address of the floating point value to be converted. These functions return the length of the resulting string.

Ieeesftos converts the 32–bit single precision floating point value f, to a string in buf, a buffer of n bytes. It returns the length of the resulting string.

Ieeedftos converts a 64–bit double precision floating point value to a character string. Buf is the address of a buffer of n characters to hold the resulting string. High and low contain the most and least significant 32 bits of the floating point value, respectively. Ieeedftos returns the number of characters in the resulting string.

SOURCE
/sys/src/libmach

SEE ALSO
mach(2), symbol(2), errstr(2)

DIAGNOSTICS
Set errstr.
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