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gdb+gdbserver/Linux: Remove USE_SIGTRAP_SIGINFO fallback

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It's been over 9 years (since commit faf09f0119da) since Linux GDB and
GDBserver started relying on SIGTRAP si_code to tell whether a
breakpoint triggered, which is important for non-stop mode.  When that
then-new code was added, I had left the then-old code as fallback, in
case some architectured still needed it.  Given AFAIK there haven't
been complaints since, this commit finally removes the fallback code,
along with USE_SIGTRAP_SIGINFO.

Change-Id: I140a5333a9fe70e90dbd186aca1f081549b2e63d
This commit is contained in:
Pedro Alves 2024-04-17 18:20:35 +01:00
parent c7d73a7157
commit 5739a1b98d
3 changed files with 8 additions and 95 deletions
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53
gdb/linux-nat.c
View File

@ -2633,18 +2633,6 @@ status_callback (struct lwp_info *lp)
discard = 1;
}
#if !USE_SIGTRAP_SIGINFO
else if (!breakpoint_inserted_here_p (lwp_inferior (lp)->aspace, pc))
{
linux_nat_debug_printf ("previous breakpoint of %s, at %s gone",
lp->ptid.to_string ().c_str (),
paddress (current_inferior ()->arch (),
lp->stop_pc));
discard = 1;
}
#endif
if (discard)
{
linux_nat_debug_printf ("pending event of %s cancelled.",
@ -2724,9 +2712,7 @@ save_stop_reason (struct lwp_info *lp)
struct gdbarch *gdbarch;
CORE_ADDR pc;
CORE_ADDR sw_bp_pc;
#if USE_SIGTRAP_SIGINFO
siginfo_t siginfo;
#endif
gdb_assert (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON);
gdb_assert (lp->status != 0);
@ -2744,7 +2730,6 @@ save_stop_reason (struct lwp_info *lp)
pc = regcache_read_pc (regcache);
sw_bp_pc = pc - gdbarch_decr_pc_after_break (gdbarch);
#if USE_SIGTRAP_SIGINFO
if (linux_nat_get_siginfo (lp->ptid, &siginfo))
{
if (siginfo.si_signo == SIGTRAP)
@ -2787,21 +2772,6 @@ save_stop_reason (struct lwp_info *lp)
}
}
}
#else
if ((!lp->step || lp->stop_pc == sw_bp_pc)
&& software_breakpoint_inserted_here_p (inf->aspace, sw_bp_pc))
{
/* The LWP was either continued, or stepped a software
breakpoint instruction. */
lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
}
if (hardware_breakpoint_inserted_here_p (inf->aspace, pc))
lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
if (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON)
check_stopped_by_watchpoint (lp);
#endif
if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
{
@ -2847,7 +2817,7 @@ linux_nat_target::stopped_by_sw_breakpoint ()
bool
linux_nat_target::supports_stopped_by_sw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
return true;
}
/* Returns true if the LWP had stopped for a hardware
@ -2868,7 +2838,7 @@ linux_nat_target::stopped_by_hw_breakpoint ()
bool
linux_nat_target::supports_stopped_by_hw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
return true;
}
/* Select one LWP out of those that have events pending. */
@ -3461,25 +3431,6 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
gdb_assert (lp != NULL);
/* Now that we've selected our final event LWP, un-adjust its PC if
it was a software breakpoint, and we can't reliably support the
"stopped by software breakpoint" stop reason. */
if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
&& !USE_SIGTRAP_SIGINFO)
{
struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
struct gdbarch *gdbarch = regcache->arch ();
int decr_pc = gdbarch_decr_pc_after_break (gdbarch);
if (decr_pc != 0)
{
CORE_ADDR pc;
pc = regcache_read_pc (regcache);
regcache_write_pc (regcache, pc + decr_pc);
}
}
/* We'll need this to determine whether to report a SIGSTOP as
GDB_SIGNAL_0. Need to take a copy because resume_clear_callback
clears it. */

11
gdb/nat/linux-ptrace.h
View File

@ -95,9 +95,9 @@
#define __WALL 0x40000000 /* Wait for any child. */
#endif
/* True if whether a breakpoint/watchpoint triggered can be determined
from the si_code of SIGTRAP's siginfo_t (TRAP_BRKPT/TRAP_HWBKPT).
That is, if the kernel can tell us whether the thread executed a
/* Whether a breakpoint/watchpoint triggered can be determined from
the si_code of SIGTRAP's siginfo_t (TRAP_BRKPT/TRAP_HWBKPT). That
is, since the kernel can tell us whether the thread executed a
software breakpoint, we trust it. The kernel will be determining
that from the hardware (e.g., from which exception was raised in
the CPU). Relying on whether a breakpoint is planted in memory at
@ -110,10 +110,7 @@
architectures. The moribund location mechanism helps with that
somewhat but it is an heuristic, and can well fail. Getting that
information out of the kernel and ultimately out of the CPU is the
way to go. That said, some architecture may get the si_code wrong,
and as such we're leaving fallback code in place. We'll remove
this after a while if no problem is reported. */
#define USE_SIGTRAP_SIGINFO 1
way to go. */
/* The x86 kernel gets some of the si_code values backwards, like
this:

39
gdbserver/linux-low.cc
View File

@ -824,9 +824,7 @@ linux_process_target::save_stop_reason (lwp_info *lwp)
{
CORE_ADDR pc;
CORE_ADDR sw_breakpoint_pc;
#if USE_SIGTRAP_SIGINFO
siginfo_t siginfo;
#endif
if (!low_supports_breakpoints ())
return false;
@ -846,7 +844,6 @@ linux_process_target::save_stop_reason (lwp_info *lwp)
scoped_restore_current_thread restore_thread;
switch_to_thread (get_lwp_thread (lwp));
#if USE_SIGTRAP_SIGINFO
if (ptrace (PTRACE_GETSIGINFO, lwpid_of (current_thread),
(PTRACE_TYPE_ARG3) 0, &siginfo) == 0)
{
@ -888,21 +885,6 @@ linux_process_target::save_stop_reason (lwp_info *lwp)
}
}
}
#else
/* We may have just stepped a breakpoint instruction. E.g., in
non-stop mode, GDB first tells the thread A to step a range, and
then the user inserts a breakpoint inside the range. In that
case we need to report the breakpoint PC. */
if ((!lwp->stepping || lwp->stop_pc == sw_breakpoint_pc)
&& low_breakpoint_at (sw_breakpoint_pc))
lwp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
if (hardware_breakpoint_inserted_here (pc))
lwp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
if (lwp->stop_reason == TARGET_STOPPED_BY_NO_REASON)
check_stopped_by_watchpoint (lwp);
#endif
if (lwp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
{
@ -1704,23 +1686,6 @@ linux_process_target::thread_still_has_status_pending (thread_info *thread)
discard = 1;
}
#if !USE_SIGTRAP_SIGINFO
else if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
&& !low_breakpoint_at (pc))
{
threads_debug_printf ("previous SW breakpoint of %ld gone",
lwpid_of (thread));
discard = 1;
}
else if (lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT
&& !hardware_breakpoint_inserted_here (pc))
{
threads_debug_printf ("previous HW breakpoint of %ld gone",
lwpid_of (thread));
discard = 1;
}
#endif
if (discard)
{
threads_debug_printf ("discarding pending breakpoint status");
@ -5652,7 +5617,7 @@ linux_process_target::stopped_by_sw_breakpoint ()
bool
linux_process_target::supports_stopped_by_sw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
return true;
}
/* Implement the stopped_by_hw_breakpoint target_ops
@ -5672,7 +5637,7 @@ linux_process_target::stopped_by_hw_breakpoint ()
bool
linux_process_target::supports_stopped_by_hw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
return true;
}
/* Implement the supports_hardware_single_step target_ops method. */