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authorDaniel Thompson <daniel.thompson@linaro.org>2020-09-27 22:15:30 +0100
committerDaniel Thompson <daniel.thompson@linaro.org>2020-10-01 14:23:21 +0100
commit4c4197eda710d197c7474abcceb3f8789ec22a64 (patch)
tree99ba58ab76ee1bac1dfeff6cb530103fdd7808e0 /kernel/debug
parentf2d10ff4a903813df767a4b56b651a26b938df06 (diff)
kgdb: Add NOKPROBE labels on the trap handler functions
Currently kgdb honours the kprobe blocklist but doesn't place its own trap handling code on the list. Add labels to discourage attempting to use kgdb to debug itself. Not every functions that executes from the trap handler needs to be marked up: relatively early in the trap handler execution (just after we bring the other CPUs to a halt) all breakpoints are replaced with the original opcodes. This patch marks up code in the debug_core that executes between trap entry and the breakpoints being deactivated and, also, code that executes between breakpoint activation and trap exit. To be clear these changes are not sufficient to make recursive trapping impossible since they do not include library calls made during kgdb's entry/exit logic. However going much further whilst we are sharing the kprobe blocklist risks reducing the capabilities of kprobe and this would be a bad trade off (especially so given kgdb's users are currently conditioned to avoid recursive traps). Reviewed-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20200927211531.1380577-3-daniel.thompson@linaro.org Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Diffstat (limited to 'kernel/debug')
-rw-r--r--kernel/debug/debug_core.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 6b9383fa8278..0761cbcbdd6d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -169,12 +169,14 @@ 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)
{
@@ -204,6 +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)
{
@@ -214,6 +217,7 @@ int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
{
return 0;
}
+NOKPROBE_SYMBOL(kgdb_skipexception);
#ifdef CONFIG_SMP
@@ -235,6 +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)
{
@@ -268,6 +273,7 @@ void __weak kgdb_roundup_cpus(void)
kgdb_info[cpu].rounding_up = false;
}
}
+NOKPROBE_SYMBOL(kgdb_roundup_cpus);
#endif
@@ -294,6 +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:
@@ -321,6 +328,7 @@ int dbg_activate_sw_breakpoints(void)
}
return ret;
}
+NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints);
int dbg_set_sw_break(unsigned long addr)
{
@@ -384,6 +392,7 @@ int dbg_deactivate_sw_breakpoints(void)
}
return ret;
}
+NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints);
int dbg_remove_sw_break(unsigned long addr)
{
@@ -505,6 +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)
{
@@ -552,6 +562,7 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
return 1;
}
+NOKPROBE_SYMBOL(kgdb_reenter_check);
static void dbg_touch_watchdogs(void)
{
@@ -559,6 +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)
@@ -790,6 +802,7 @@ kgdb_restore:
return kgdb_info[cpu].ret_state;
}
+NOKPROBE_SYMBOL(kgdb_cpu_enter);
/*
* kgdb_handle_exception() - main entry point from a kernel exception
@@ -834,6 +847,7 @@ 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.
@@ -868,6 +882,7 @@ 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)
@@ -893,6 +908,7 @@ 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)