static bool
event_pre_syscall(void *drcontext, int sysnum)
{
bool modify_write = (sysnum == write_sysnum);
dr_atomic_add32_return_sum(&num_syscalls, 1);
#ifdef UNIX
if (sysnum == SYS_execve) {
/* our stats will be re-set post-execve so display now */
show_results();
# ifdef SHOW_RESULTS
dr_fprintf(STDERR, "<---- execve ---->\n");
# endif
}
#endif
#ifndef SHOW_RESULTS
/* for sanity tests that don't show results we don't change the app's output */
modify_write = false;
#endif
if (modify_write) {
/* store params for access post-syscall */
int i;
per_thread_t *data = (per_thread_t *) drmgr_get_cls_field(drcontext, tcls_idx);
#ifdef WINDOWS
/* stderr and stdout are identical in our cygwin rxvt shell so for
* our example we suppress output starting with 'H' instead
*/
byte *output = (byte *) dr_syscall_get_param(drcontext, 5);
byte first;
size_t read;
bool ok = dr_safe_read(output, 1, &first, &read);
if (!ok || read != 1)
return true; /* data unreadable: execute normally */
if (dr_is_wow64()) {
/* store the xcx emulation parameter for wow64 */
dr_mcontext_t mc = {sizeof(mc),DR_MC_INTEGER/*only need xcx*/};
dr_get_mcontext(drcontext, &mc);
data->xcx = mc.xcx;
}
#endif
for (i = 0; i < SYS_MAX_ARGS; i++)
data->param[i] = dr_syscall_get_param(drcontext, i);
/* suppress stderr */
if (dr_syscall_get_param(drcontext, 0) == (reg_t) STDERR
#ifdef WINDOWS
&& first == 'H'
#endif
) {
/* pretend it succeeded */
#ifdef UNIX
/* return the #bytes == 3rd param */
dr_syscall_result_info_t info = { sizeof(info), };
info.succeeded = true;
info.value = dr_syscall_get_param(drcontext, 2);
dr_syscall_set_result_ex(drcontext, &info);
#else
/* XXX: we should also set the IO_STATUS_BLOCK.Information field */
dr_syscall_set_result(drcontext, 0);
#endif
#ifdef SHOW_RESULTS
dr_fprintf(STDERR, "<---- skipping write to stderr ---->\n");
#endif
return false; /* skip syscall */
} else if (dr_syscall_get_param(drcontext, 0) == (reg_t) STDOUT) {
if (!data->repeat) {
/* redirect stdout to stderr (unless it's our repeat) */
#ifdef SHOW_RESULTS
dr_fprintf(STDERR, "<---- changing stdout to stderr ---->\n");
#endif
dr_syscall_set_param(drcontext, 0, (reg_t) STDERR);
}
/* we're going to repeat this syscall once */
data->repeat = !data->repeat;
}
}
return true; /* execute normally */
}
static bool
event_pre_syscall(void *drcontext, int sysnum)
{
ATOMIC_INC(num_syscalls);
#ifdef LINUX
if (sysnum == SYS_execve) {
/* our stats will be re-set post-execve so display now */
show_results();
# ifdef SHOW_RESULTS
dr_fprintf(STDERR, "<---- execve ---->\n");
# endif
}
#endif
#ifdef SHOW_RESULTS
dr_fprintf(STDERR, "[%d] "PFX" "PFX" "PFX"\n",
sysnum,
dr_syscall_get_param(drcontext, 0),
dr_syscall_get_param(drcontext, 1),
dr_syscall_get_param(drcontext, 2));
#endif
if (sysnum == write_sysnum) {
/* store params for access post-syscall */
int i;
per_thread_t *data = (per_thread_t *) drmgr_get_cls_field(drcontext, tcls_idx);
#ifdef WINDOWS
/* stderr and stdout are identical in our cygwin rxvt shell so for
* our example we suppress output starting with 'H' instead
*/
byte *output = (byte *) dr_syscall_get_param(drcontext, 5);
byte first;
size_t read;
bool ok = dr_safe_read(output, 1, &first, &read);
if (!ok || read != 1)
return true; /* data unreadable: execute normally */
if (dr_is_wow64()) {
/* store the xcx emulation parameter for wow64 */
dr_mcontext_t mc = {sizeof(mc),DR_MC_INTEGER/*only need xcx*/};
dr_get_mcontext(drcontext, &mc);
data->xcx = mc.xcx;
}
#endif
for (i = 0; i < SYS_MAX_ARGS; i++)
data->param[i] = dr_syscall_get_param(drcontext, i);
/* suppress stderr */
if (dr_syscall_get_param(drcontext, 0) == (reg_t) STDERR
#ifdef WINDOWS
&& first == 'H'
#endif
) {
/* pretend it succeeded */
#ifdef LINUX
/* return the #bytes == 3rd param */
dr_syscall_set_result(drcontext, dr_syscall_get_param(drcontext, 2));
#else
/* we should also set the IO_STATUS_BLOCK.Information field */
dr_syscall_set_result(drcontext, 0);
#endif
#ifdef SHOW_RESULTS
dr_fprintf(STDERR, " [%d] => skipped\n", sysnum);
#endif
return false; /* skip syscall */
} else if (dr_syscall_get_param(drcontext, 0) == (reg_t) STDOUT) {
if (!data->repeat) {
/* redirect stdout to stderr (unless it's our repeat) */
#ifdef SHOW_RESULTS
dr_fprintf(STDERR, " [%d] STDOUT => STDERR\n", sysnum);
#endif
dr_syscall_set_param(drcontext, 0, (reg_t) STDERR);
}
/* we're going to repeat this syscall once */
data->repeat = !data->repeat;
}
}
return true; /* execute normally */
}