From f2d10ff4a903813df767a4b56b651a26b938df06 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Sun, 27 Sep 2020 22:15:29 +0100 Subject: kgdb: Honour the kprobe blocklist when setting breakpoints Currently kgdb has absolutely no safety rails in place to discourage or prevent a user from placing a breakpoint in dangerous places such as the debugger's own trap entry/exit and other places where it is not safe to take synchronous traps. Introduce a new config symbol KGDB_HONOUR_BLOCKLIST and modify the default implementation of kgdb_validate_break_address() so that we use the kprobe blocklist to prohibit instrumentation of critical functions if the config symbol is set. The config symbol dependencies are set to ensure that the blocklist will be enabled by default if we enable KGDB and are compiling for an architecture where we HAVE_KPROBES. Suggested-by: Peter Zijlstra Reviewed-by: Douglas Anderson Reviewed-by: Masami Hiramatsu Link: https://lore.kernel.org/r/20200927211531.1380577-2-daniel.thompson@linaro.org Signed-off-by: Daniel Thompson --- lib/Kconfig.kgdb | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'lib/Kconfig.kgdb') 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 -- cgit