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-rw-r--r--include/linux/kgdb.h18
-rw-r--r--kernel/debug/debug_core.c48
-rw-r--r--kernel/debug/gdbstub.c5
-rw-r--r--kernel/debug/kdb/kdb_bp.c9
-rw-r--r--kernel/debug/kdb/kdb_bt.c4
-rw-r--r--kernel/debug/kdb/kdb_debugger.c2
-rw-r--r--kernel/debug/kdb/kdb_io.c22
-rw-r--r--kernel/debug/kdb/kdb_main.c8
-rw-r--r--kernel/debug/kdb/kdb_private.h4
-rw-r--r--lib/Kconfig.kgdb15
10 files changed, 101 insertions, 34 deletions
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 477b8b7c908f..0d6cf64c8bb1 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -16,6 +16,7 @@
#include <linux/linkage.h>
#include <linux/init.h>
#include <linux/atomic.h>
+#include <linux/kprobes.h>
#ifdef CONFIG_HAVE_ARCH_KGDB
#include <asm/kgdb.h>
#endif
@@ -335,6 +336,23 @@ extern int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
atomic_t *snd_rdy);
extern void gdbstub_exit(int status);
+/*
+ * kgdb and kprobes both use the same (kprobe) blocklist (which makes sense
+ * given they are both typically hooked up to the same trap meaning on most
+ * architectures one cannot be used to debug the other)
+ *
+ * However on architectures where kprobes is not (yet) implemented we permit
+ * breakpoints everywhere rather than blocking everything by default.
+ */
+static inline bool kgdb_within_blocklist(unsigned long addr)
+{
+#ifdef CONFIG_KGDB_HONOUR_BLOCKLIST
+ return within_kprobe_blacklist(addr);
+#else
+ return false;
+#endif
+}
+
extern int kgdb_single_step;
extern atomic_t kgdb_active;
#define in_dbg_master() \
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index b16dbc1bf056..1e75a8923a8d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -80,7 +80,7 @@ static int exception_level;
struct kgdb_io *dbg_io_ops;
static DEFINE_SPINLOCK(kgdb_registration_lock);
-/* Action for the reboot notifiter, a global allow kdb to change it */
+/* Action for the reboot notifier, a global allow kdb to change it */
static int kgdbreboot;
/* kgdb console driver is loaded */
static int kgdb_con_registered;
@@ -94,14 +94,6 @@ int dbg_switch_cpu;
/* Use kdb or gdbserver mode */
int dbg_kdb_mode = 1;
-static int __init opt_kgdb_con(char *str)
-{
- kgdb_use_con = 1;
- return 0;
-}
-
-early_param("kgdbcon", opt_kgdb_con);
-
module_param(kgdb_use_con, int, 0644);
module_param(kgdbreboot, int, 0644);
@@ -163,7 +155,7 @@ early_param("nokgdbroundup", opt_nokgdbroundup);
/*
* Weak aliases for breakpoint management,
- * can be overriden by architectures when needed:
+ * can be overridden by architectures when needed:
*/
int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
@@ -177,17 +169,23 @@ int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
return err;
}
+NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint);
int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
return copy_to_kernel_nofault((char *)bpt->bpt_addr,
(char *)bpt->saved_instr, BREAK_INSTR_SIZE);
}
+NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint);
int __weak kgdb_validate_break_address(unsigned long addr)
{
struct kgdb_bkpt tmp;
int err;
+
+ if (kgdb_within_blocklist(addr))
+ return -EINVAL;
+
/* Validate setting the breakpoint and then removing it. If the
* remove fails, the kernel needs to emit a bad message because we
* are deep trouble not being able to put things back the way we
@@ -208,6 +206,7 @@ unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
{
return instruction_pointer(regs);
}
+NOKPROBE_SYMBOL(kgdb_arch_pc);
int __weak kgdb_arch_init(void)
{
@@ -218,6 +217,7 @@ int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
{
return 0;
}
+NOKPROBE_SYMBOL(kgdb_skipexception);
#ifdef CONFIG_SMP
@@ -239,6 +239,7 @@ void __weak kgdb_call_nmi_hook(void *ignored)
*/
kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
}
+NOKPROBE_SYMBOL(kgdb_call_nmi_hook);
void __weak kgdb_roundup_cpus(void)
{
@@ -272,6 +273,7 @@ void __weak kgdb_roundup_cpus(void)
kgdb_info[cpu].rounding_up = false;
}
}
+NOKPROBE_SYMBOL(kgdb_roundup_cpus);
#endif
@@ -298,6 +300,7 @@ static void kgdb_flush_swbreak_addr(unsigned long addr)
/* Force flush instruction cache if it was outside the mm */
flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
}
+NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr);
/*
* SW breakpoint management:
@@ -325,6 +328,7 @@ int dbg_activate_sw_breakpoints(void)
}
return ret;
}
+NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
int dbg_set_sw_break(unsigned long addr)
{
@@ -388,6 +392,7 @@ int dbg_deactivate_sw_breakpoints(void)
}
return ret;
}
+NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
int dbg_remove_sw_break(unsigned long addr)
{
@@ -509,6 +514,7 @@ static int kgdb_io_ready(int print_wait)
}
return 1;
}
+NOKPROBE_SYMBOL(kgdb_io_ready);
static int kgdb_reenter_check(struct kgdb_state *ks)
{
@@ -556,6 +562,7 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
return 1;
}
+NOKPROBE_SYMBOL(kgdb_reenter_check);
static void dbg_touch_watchdogs(void)
{
@@ -563,6 +570,7 @@ static void dbg_touch_watchdogs(void)
clocksource_touch_watchdog();
rcu_cpu_stall_reset();
}
+NOKPROBE_SYMBOL(dbg_touch_watchdogs);
static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
int exception_state)
@@ -752,6 +760,8 @@ cpu_master_loop:
}
}
+ dbg_activate_sw_breakpoints();
+
/* Call the I/O driver's post_exception routine */
if (dbg_io_ops->post_exception)
dbg_io_ops->post_exception();
@@ -794,6 +804,7 @@ kgdb_restore:
return kgdb_info[cpu].ret_state;
}
+NOKPROBE_SYMBOL(kgdb_cpu_enter);
/*
* kgdb_handle_exception() - main entry point from a kernel exception
@@ -838,6 +849,7 @@ out:
arch_kgdb_ops.enable_nmi(1);
return ret;
}
+NOKPROBE_SYMBOL(kgdb_handle_exception);
/*
* GDB places a breakpoint at this function to know dynamically loaded objects.
@@ -872,6 +884,7 @@ int kgdb_nmicallback(int cpu, void *regs)
#endif
return 1;
}
+NOKPROBE_SYMBOL(kgdb_nmicallback);
int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
atomic_t *send_ready)
@@ -897,6 +910,7 @@ int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
#endif
return 1;
}
+NOKPROBE_SYMBOL(kgdb_nmicallin);
static void kgdb_console_write(struct console *co, const char *s,
unsigned count)
@@ -920,6 +934,20 @@ static struct console kgdbcons = {
.index = -1,
};
+static int __init opt_kgdb_con(char *str)
+{
+ kgdb_use_con = 1;
+
+ if (kgdb_io_module_registered && !kgdb_con_registered) {
+ register_console(&kgdbcons);
+ kgdb_con_registered = 1;
+ }
+
+ return 0;
+}
+
+early_param("kgdbcon", opt_kgdb_con);
+
#ifdef CONFIG_MAGIC_SYSRQ
static void sysrq_handle_dbg(int key)
{
diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index cc3c43dfec44..a77df59d9ca5 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -725,7 +725,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
}
}
- do_each_thread(g, p) {
+ for_each_process_thread(g, p) {
if (i >= ks->thr_query && !finished) {
int_to_threadref(thref, p->pid);
ptr = pack_threadid(ptr, thref);
@@ -735,7 +735,7 @@ static void gdb_cmd_query(struct kgdb_state *ks)
finished = 1;
}
i++;
- } while_each_thread(g, p);
+ }
*(--ptr) = '\0';
break;
@@ -1061,7 +1061,6 @@ int gdb_serial_stub(struct kgdb_state *ks)
error_packet(remcom_out_buffer, -EINVAL);
break;
}
- dbg_activate_sw_breakpoints();
fallthrough; /* to default processing */
default:
default_handle:
diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c
index d7ebb2c79cb8..ec4940146612 100644
--- a/kernel/debug/kdb/kdb_bp.c
+++ b/kernel/debug/kdb/kdb_bp.c
@@ -307,6 +307,15 @@ static int kdb_bp(int argc, const char **argv)
return KDB_BADINT;
/*
+ * This check is redundant (since the breakpoint machinery should
+ * be doing the same check during kdb_bp_install) but gives the
+ * user immediate feedback.
+ */
+ diag = kgdb_validate_break_address(template.bp_addr);
+ if (diag)
+ return diag;
+
+ /*
* Find an empty bp structure to allocate
*/
for (bpno = 0, bp = kdb_breakpoints; bpno < KDB_MAXBPT; bpno++, bp++) {
diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 18e03aba2cfc..1f9f0e47aeda 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -149,14 +149,14 @@ kdb_bt(int argc, const char **argv)
return 0;
}
/* Now the inactive tasks */
- kdb_do_each_thread(g, p) {
+ for_each_process_thread(g, p) {
if (KDB_FLAG(CMD_INTERRUPT))
return 0;
if (task_curr(p))
continue;
if (kdb_bt1(p, mask, btaprompt))
return 0;
- } kdb_while_each_thread(g, p);
+ }
} else if (strcmp(argv[0], "btp") == 0) {
struct task_struct *p;
unsigned long pid;
diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c
index 53a0df6e4d92..0220afda3200 100644
--- a/kernel/debug/kdb/kdb_debugger.c
+++ b/kernel/debug/kdb/kdb_debugger.c
@@ -147,7 +147,6 @@ int kdb_stub(struct kgdb_state *ks)
return DBG_PASS_EVENT;
}
kdb_bp_install(ks->linux_regs);
- dbg_activate_sw_breakpoints();
/* Set the exit state to a single step or a continue */
if (KDB_STATE(DOING_SS))
gdbstub_state(ks, "s");
@@ -167,7 +166,6 @@ int kdb_stub(struct kgdb_state *ks)
* differently vs the gdbstub
*/
kgdb_single_step = 0;
- dbg_deactivate_sw_breakpoints();
return DBG_SWITCH_CPU_EVENT;
}
return kgdb_info[ks->cpu].ret_state;
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 9d847ab851db..6735ac36b718 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -545,18 +545,18 @@ static int kdb_search_string(char *searched, char *searchfor)
static void kdb_msg_write(const char *msg, int msg_len)
{
struct console *c;
+ const char *cp;
+ int len;
if (msg_len == 0)
return;
- if (dbg_io_ops) {
- const char *cp = msg;
- int len = msg_len;
+ cp = msg;
+ len = msg_len;
- while (len--) {
- dbg_io_ops->write_char(*cp);
- cp++;
- }
+ while (len--) {
+ dbg_io_ops->write_char(*cp);
+ cp++;
}
for_each_console(c) {
@@ -706,12 +706,16 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
size_avail = sizeof(kdb_buffer) - len;
goto kdb_print_out;
}
- if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH)
+ if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH) {
/*
* This was a interactive search (using '/' at more
- * prompt) and it has completed. Clear the flag.
+ * prompt) and it has completed. Replace the \0 with
+ * its original value to ensure multi-line strings
+ * are handled properly, and return to normal mode.
*/
+ *cphold = replaced_byte;
kdb_grepping_flag = 0;
+ }
/*
* at this point the string is a full line and
* should be printed, up to the null.
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 5c7949061671..930ac1b25ec7 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2299,10 +2299,10 @@ void kdb_ps_suppressed(void)
if (kdb_task_state(p, mask_I))
++idle;
}
- kdb_do_each_thread(g, p) {
+ for_each_process_thread(g, p) {
if (kdb_task_state(p, mask_M))
++daemon;
- } kdb_while_each_thread(g, p);
+ }
if (idle || daemon) {
if (idle)
kdb_printf("%d idle process%s (state I)%s\n",
@@ -2370,12 +2370,12 @@ static int kdb_ps(int argc, const char **argv)
}
kdb_printf("\n");
/* Now the real tasks */
- kdb_do_each_thread(g, p) {
+ for_each_process_thread(g, p) {
if (KDB_FLAG(CMD_INTERRUPT))
return 0;
if (kdb_task_state(p, mask))
kdb_ps1(p);
- } kdb_while_each_thread(g, p);
+ }
return 0;
}
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 2e296e4a234c..a4281fb99299 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -230,10 +230,6 @@ extern struct task_struct *kdb_curr_task(int);
#define kdb_task_has_cpu(p) (task_curr(p))
-/* Simplify coexistence with NPTL */
-#define kdb_do_each_thread(g, p) do_each_thread(g, p)
-#define kdb_while_each_thread(g, p) while_each_thread(g, p)
-
#define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
extern void *debug_kmalloc(size_t size, gfp_t flags);
diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
index 256f2486f9bd..05dae05b6cc9 100644
--- a/lib/Kconfig.kgdb
+++ b/lib/Kconfig.kgdb
@@ -24,6 +24,21 @@ menuconfig KGDB
if KGDB
+config KGDB_HONOUR_BLOCKLIST
+ bool "KGDB: use kprobe blocklist to prohibit unsafe breakpoints"
+ depends on HAVE_KPROBES
+ depends on MODULES
+ select KPROBES
+ default y
+ help
+ If set to Y the debug core will use the kprobe blocklist to
+ identify symbols where it is unsafe to set breakpoints.
+ In particular this disallows instrumentation of functions
+ called during debug trap handling and thus makes it very
+ difficult to inadvertently provoke recursive trap handling.
+
+ If unsure, say Y.
+
config KGDB_SERIAL_CONSOLE
tristate "KGDB: use kgdb over the serial console"
select CONSOLE_POLL

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