/** Gets user space registers when available, also sets context
* full_uregs_p if appropriate. Should be used instead of accessing
* context uregs field directly when (full) uregs are needed from
* kernel context.
*/
static struct pt_regs *_stp_get_uregs(struct context *c)
{
/* When the probe occurred in user context uregs are always complete. */
if (c->uregs && c->user_mode_p)
c->full_uregs_p = 1;
else if (c->uregs == NULL)
{
dbug_unwind(1, "computing uregs\n");
/* First try simple recovery through task_pt_regs,
on some platforms that already provides complete uregs. */
c->uregs = _stp_current_pt_regs();
if (c->uregs && _stp_task_pt_regs_valid(current, c->uregs))
c->full_uregs_p = 1;
/* Sadly powerpc does support the dwarf unwinder, but doesn't have enough
CFI in the kernel to recover fully to user space. */
#if defined(STP_USE_DWARF_UNWINDER) && !defined (__powerpc__)
else if (c->uregs != NULL && c->kregs != NULL && !c->user_mode_p)
{
struct unwind_frame_info *info = &c->uwcontext_kernel.info;
int ret = 0;
int levels;
/* We might be lucky and this probe already ran the kernel
unwind to end up in the user regs. */
if (UNW_PC(info) == REG_IP(c->uregs))
{
levels = 0;
dbug_unwind(1, "feeling lucky, info pc == uregs pc\n");
}
else
{
/* Try to recover the uregs by unwinding from the the kernel
probe location. */
levels = MAXBACKTRACE;
arch_unw_init_frame_info(info, c->kregs, 0);
dbug_unwind(1, "Trying to recover... searching for 0x%llx\n",
(unsigned long long) REG_IP(c->uregs));
/* Mark the kernel unwind cache as invalid
(uwcache_kernel.depth is no longer consistent with
the actual current depth of the unwind).
We don't save PCs in the cache at this point because
this kernel unwind procedure does not fetch the top
level PC, so uwcache_kernel.pc[0] would be left
unpopulated. We would have to either fetch the
current PC here, or specially represent this state of
the cache, something we don't bother with at this
stage.
XXX: this can create (tolerable amounts of) inefficiency
if the probe intersperses user and kernel unwind calls,
since the other unwind code can clear uregs, triggering
a redundant unwind the next time we need them. */
dbug_unwind(1, "clearing kernel unwind cache\n");
c->uwcache_kernel.state = uwcache_uninitialized;
}
while (levels > 0 && ret == 0 && UNW_PC(info) != REG_IP(c->uregs))
{
levels--;
ret = unwind(&c->uwcontext_kernel, 0);
dbug_unwind(1, "unwind levels: %d, ret: %d, pc=0x%llx\n",
levels, ret, (unsigned long long) UNW_PC(info));
}
/* Have we arrived where we think user space currently is? */
if (ret == 0 && UNW_PC(info) == REG_IP(c->uregs))
{
/* Note we need to clear this state again when the unwinder
has been rerun. See __stp_stack_print invocation below. */
UNW_SP(info) = REG_SP(c->uregs); /* Fix up user stack */
c->uregs = &info->regs;
c->full_uregs_p = 1;
dbug_unwind(1, "recovered with pc=0x%llx sp=0x%llx\n",
(unsigned long long) UNW_PC(info),
(unsigned long long) UNW_SP(info));
}
else
dbug_unwind(1, "failed to recover user reg state\n");
}
#endif
}
return c->uregs;
}
/** Gets user space registers when available, also sets context probe_flags
* _STP_PROBE_STATE_FULL_UREGS if appropriate. Should be used instead of
* accessing context uregs field directly when (full) uregs are needed
* from kernel context.
*/
static struct pt_regs *_stp_get_uregs(struct context *c)
{
/* When the probe occurred in user context uregs are always complete. */
if (c->uregs && c->probe_flags & _STP_PROBE_STATE_USER_MODE)
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
else if (c->uregs == NULL)
{
/* First try simple recovery through task_pt_regs,
on some platforms that already provides complete uregs. */
c->uregs = _stp_current_pt_regs();
if (c->uregs && _stp_task_pt_regs_valid(current, c->uregs))
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
/* Sadly powerpc does support the dwarf unwinder, but doesn't have enough
CFI in the kernel to recover fully to user space. */
#if defined(STP_USE_DWARF_UNWINDER) && !defined (__powerpc__)
else if (c->uregs != NULL && c->kregs != NULL
&& ! (c->probe_flags & _STP_PROBE_STATE_USER_MODE))
{
struct unwind_frame_info *info = &c->uwcontext.info;
int ret = 0;
int levels;
/* We might be lucky and this probe already ran the kernel
unwind to end up in the user regs. */
if (UNW_PC(info) == REG_IP(c->uregs))
{
levels = 0;
dbug_unwind(1, "feeling lucky, info pc == uregs pc\n");
}
else
{
/* Try to recover the uregs by unwinding from the the kernel
probe location. */
levels = MAXBACKTRACE;
arch_unw_init_frame_info(info, c->kregs, 0);
dbug_unwind(1, "Trying to recover... searching for 0x%lx\n",
REG_IP(c->uregs));
}
while (levels > 0 && ret == 0 && UNW_PC(info) != REG_IP(c->uregs))
{
levels--;
ret = unwind(&c->uwcontext, 0);
dbug_unwind(1, "unwind levels: %d, ret: %d, pc=0x%lx\n",
levels, ret, UNW_PC(info));
}
/* Have we arrived where we think user space currently is? */
if (ret == 0 && UNW_PC(info) == REG_IP(c->uregs))
{
/* Note we need to clear this state again when the unwinder
has been rerun. See __stp_stack_print invocation below. */
UNW_SP(info) = REG_SP(c->uregs); /* Fix up user stack */
c->uregs = &info->regs;
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
dbug_unwind(1, "recovered with pc=0x%lx sp=0x%lx\n",
UNW_PC(info), UNW_SP(info));
}
else
dbug_unwind(1, "failed to recover user reg state\n");
}
#endif
}
return c->uregs;
}
