Debugger Import Interface

The imported interface that a controlling process must provide to librtld_db.so.1 is defined in /usr/include/proc_service.h. A sample implementation of these proc_service functions can be found in the rdb demonstration debugger. The rtld-debugger interface uses only a subset of the proc_service interfaces available. Future versions of the rtld-debugger interface might take advantage of additional proc_service interfaces without creating an incompatible change.

The following interfaces are currently being used by the rtld-debugger interface:

ps_pauxv()

ps_err_e ps_pauxv(const struct ps_prochandle * ph, auxv_t ** aux);

This function returns a pointer to a copy of the auxv vector. As the auxv vector information is copied to an allocated structure, the life time of this pointer is as long as the ps_prochandle is valid.

ps_pread()

ps_err_e ps_pread(const struct ps_prochandle * ph, paddr_t addr, char * buf, int size);

This function reads size bytes from the target process at address addr and copies them into buf.

ps_pwrite()

ps_err_e ps_pwrite(const struct ps_prochandle * ph, paddr_t addr, char * buf, int size);

This function writes size bytes from buf into the target process at address addr.

ps_plog()

void ps_plog(const char * fmt, ...);

This function is called with additional diagnostic information from the rtld-debugger interface. It is up to the controlling process to decide where (or if) to log this diagnostic information. The arguments to ps_plog() follow the printf(3C) format.

ps_pglobal_lookup()

ps_err_e ps_pglobal_lookup(const struct ps_prochandle * ph, const char * obj, const char * name, ulong_t * sym_addr);

This function searches for the symbol named name within the object named obj within the target process ph. If the symbol is found address of the symbol is stored in sym_addr.

ps_pglobal_sym()

ps_err_e ps_pglobal_sym(const struct ps_prochandle * ph, const char * obj, const char * name, ps_sym_t * sym);

This function searches for the symbol named name within the object named obj within the target process ph. If the symbol is found, the descriptor sym is filled in.

In the event that the rtld-debugger interface needs to find symbols within the application or runtime linker prior to any link-map creation, the following reserved values for obj are available:

#define PS_OBJ_EXEC ((const char *)0x0)  /* application id */
#define PS_OBJ_LDSO ((const char *)0x1)  /* runtime linker id */

One mechanism the controlling process can use to find the symbol table for these objects is through the procfs file system using the following pseudo code:

ioctl(.., PIOCNAUXV, ...)       - obtain AUX vectors
ldsoaddr = auxv[AT_BASE];
ldsofd = ioctl(..., PIOCOPENM, &ldsoaddr);
 
/* process elf information found in ldsofd ... */
 
execfd = ioctl(.., PIOCOPENM, 0);
 
/* process elf information found in execfd ... */

Once the file descriptors are found, the ELF files can be examined for their symbol information by the controlling program.