term% ls -F
term% cat index.txt
DEBUGGER(2)                   System Calls Manual                  DEBUGGER(2)

       cisctrace,  risctrace,  ciscframe, riscframe, localaddr, symoff, fpfor‐
       mat, beieee80ftos, beieeesftos, beieeedftos, leieee80ftos, leieeesftos,
       leieeedftos,  ieeesftos, ieeedftos - machine-independent debugger func‐

       #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;

       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  de‐
       scribing  the target architecture.  The former contains machine parame‐
       ters and a description of the register set; it is usually set by invok‐
       ing  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 architec‐
       ture.  Each application is responsible for setting machdata to the  ad‐
       dress  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 exe‐
       cuting image.  The Map (see mach(2)) data structure supports  the  con‐
       sistent  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 un‐
       winding is to take place.  Normally, they are the current  contents  of
       the appropriate registers but they can be any values defining a legiti‐
       mate 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 pro‐
       totype 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 ta‐
       ble 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 execut‐
       ing 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 indi‐
       cates 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  dou‐
       ble  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 ar‐
       chitectures that implement double precision floats by  combining  adja‐
       cent single precision registers.  For code f, the specified register is
       formatted as a single precision float.  Fpformat returns 1 if the  num‐
       ber is successfully converted or -1 in the case of an error.

       Beieee80ftos, beieeesftos and beieeedftos convert big-endian 80-bit ex‐
       tended, 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.


       mach(2), symbol(2), errstr(2)

       Set errstr.