kernel/linux.git/include/linux/kgdb.h, branch v6.6.132

kgdb: Provide a stub kgdb_nmicallback() if !CONFIG_KGDB

2023-06-29T14:06:32+00:00

To save architectures from needing to wrap the call in #ifdefs, add a stub no-op version of kgdb_nmicallback(), which returns 1 if it didn't handle anything. Reviewed-by: Daniel Thompson Signed-off-by: Douglas Anderson Link: https://lore.kernel.org/r/20230601143109.v9.6.Ia3aeac89bb6751b682237e76e5ba594318e4b1aa@changeid Signed-off-by: Daniel Thompson

kgdb: Fix spelling mistakes

2021-06-01T09:29:21+00:00

Fix some spelling mistakes in comments: initalization ==> initialization detatch ==> detach represntation ==> representation hexidecimal ==> hexadecimal delimeter ==> delimiter architecure ==> architecture Signed-off-by: Zhen Lei Link: https://lore.kernel.org/r/20210529110305.9446-3-thunder.leizhen@huawei.com Signed-off-by: Daniel Thompson

kgdb: fix to kill breakpoints on initmem after boot

2021-02-26T17:41:05+00:00

Currently breakpoints in kernel .init.text section are not handled correctly while allowing to remove them even after corresponding pages have been freed. Fix it via killing .init.text section breakpoints just prior to initmem pages being freed. Doug: "HW breakpoints aren't handled by this patch but it's probably not such a big deal". Link: https://lkml.kernel.org/r/20210224081652.587785-1-sumit.garg@linaro.org Signed-off-by: Sumit Garg Suggested-by: Doug Anderson Acked-by: Doug Anderson Acked-by: Daniel Thompson Tested-by: Daniel Thompson Cc: Masami Hiramatsu Cc: Steven Rostedt (VMware) Cc: Jason Wessel Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kgdb: Remove kgdb_schedule_breakpoint()

2021-02-11T10:51:56+00:00

To the very best of my knowledge there has never been any in-tree code that calls this function. It exists largely to support an out-of-tree driver that provides kgdb-over-ethernet using the netpoll API. kgdboe has been out-of-tree for more than 10 years and I don't recall any serious attempt to upstream it at any point in the last five. At this stage it looks better to stop carrying this code in the kernel and integrate the code into the out-of-tree driver instead. The long term trajectory for the kernel looks likely to include effort to remove or reduce the use of tasklets (something that has also been true for the last 10 years). Thus the main real reason for this patch is to make explicit that the in-tree kgdb features do not require tasklets. Signed-off-by: Daniel Thompson Link: https://lore.kernel.org/r/20210210142525.2876648-1-daniel.thompson@linaro.org Reviewed-by: Douglas Anderson Acked-by: Davidlohr Bueso Acked-by: Jason Wessel

kgdb: Honour the kprobe blocklist when setting breakpoints

2020-09-28T11:14:08+00:00

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

kgdb: Move the extern declaration kgdb_has_hit_break() to generic kgdb.h

2020-07-10T03:12:19+00:00

Currently, only riscv kgdb.c uses the kgdb_has_hit_break() to identify the kgdb breakpoint. It causes other architectures will encounter the "no previous prototype" warnings if the compile option has W=1. Moving the declaration of extern kgdb_has_hit_break() from risc-v kgdb.h to generic kgdb.h to avoid generating these warnings. Signed-off-by: Vincent Chen Acked-by: Daniel Thompson Signed-off-by: Palmer Dabbelt

kgdb: enable arch to support XML packet.

2020-07-10T03:09:28+00:00

The XML packet could be supported by required architecture if the architecture defines CONFIG_HAVE_ARCH_KGDB_QXFER_PKT and implement its own kgdb_arch_handle_qxfer_pkt(). Except for the kgdb_arch_handle_qxfer_pkt(), the architecture also needs to record the feature supported by gdb stub into the kgdb_arch_gdb_stub_feature, and these features will be reported to host gdb when gdb stub receives the qSupported packet. Signed-off-by: Vincent Chen Acked-by: Daniel Thompson Signed-off-by: Palmer Dabbelt

kdb: Switch to use safer dbg_io_ops over console APIs

2020-06-26T14:40:16+00:00

In kgdb context, calling console handlers aren't safe due to locks used in those handlers which could in turn lead to a deadlock. Although, using oops_in_progress increases the chance to bypass locks in most console handlers but it might not be sufficient enough in case a console uses more locks (VT/TTY is good example). Currently when a driver provides both polling I/O and a console then kdb will output using the console. We can increase robustness by using the currently active polling I/O driver (which should be lockless) instead of the corresponding console. For several common cases (e.g. an embedded system with a single serial port that is used both for console output and debugger I/O) this will result in no console handler being used. In order to achieve this we need to reverse the order of preference to use dbg_io_ops (uses polling I/O mode) over console APIs. So we just store "struct console" that represents debugger I/O in dbg_io_ops and while emitting kdb messages, skip console that matches dbg_io_ops console in order to avoid duplicate messages. After this change, "is_console" param becomes redundant and hence removed. Suggested-by: Daniel Thompson Signed-off-by: Sumit Garg Link: https://lore.kernel.org/r/1591264879-25920-5-git-send-email-sumit.garg@linaro.org Reviewed-by: Douglas Anderson Reviewed-by: Petr Mladek Acked-by: Greg Kroah-Hartman Signed-off-by: Daniel Thompson

kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles

2020-05-18T16:49:27+00:00

We want to enable kgdb to debug the early parts of the kernel. Unfortunately kgdb normally is a client of the tty API in the kernel and serial drivers don't register to the tty layer until fairly late in the boot process. Serial drivers do, however, commonly register a boot console. Let's enable the kgdboc driver to work with boot consoles to provide early debugging. This change co-opts the existing read() function pointer that's part of "struct console". It's assumed that if a boot console (with the flag CON_BOOT) has implemented read() that both the read() and write() function are polling functions. That means they work without interrupts and read() will return immediately (with 0 bytes read) if there's nothing to read. This should be a safe assumption since it appears that no current boot consoles implement read() right now and there seems no reason to do so unless they wanted to support "kgdboc_earlycon". The normal/expected way to make all this work is to use "kgdboc_earlycon" and "kgdboc" together. You should point them both to the same physical serial connection. At boot time, as the system transitions from the boot console to the normal console (and registers a tty), kgdb will switch over. One awkward part of all this, though, is that there can be a window where the boot console goes away and we can't quite transtion over to the main kgdboc that uses the tty layer. There are two main problems: 1. The act of registering the tty doesn't cause any call into kgdboc so there is a window of time when the tty is there but kgdboc's init code hasn't been called so we can't transition to it. 2. On some serial drivers the normal console inits (and replaces the boot console) quite early in the system. Presumably these drivers were coded up before earlycon worked as well as it does today and probably they don't need to do this anymore, but it causes us problems nontheless. Problem #1 is not too big of a deal somewhat due to the luck of probe ordering. kgdboc is last in the tty/serial/Makefile so its probe gets right after all other tty devices. It's not fun to rely on this, but it does work for the most part. Problem #2 is a big deal, but only for some serial drivers. Other serial drivers end up registering the console (which gets rid of the boot console) and tty at nearly the same time. The way we'll deal with the window when the system has stopped using the boot console and the time when we're setup using the tty is to keep using the boot console. This may sound surprising, but it has been found to work well in practice. If it doesn't work, it shouldn't be too hard for a given serial driver to make it keep working. Specifically, it's expected that the read()/write() function provided in the boot console should be the same (or nearly the same) as the normal kgdb polling functions. That means continuing to use them should work just fine. To make things even more likely to work work we'll also trap the recently added exit() function in the boot console we're using and delay any calls to it until we're all done with the boot console. NOTE: there could be ways to use all this in weird / unexpected ways. If you do something like this, it's a bit of a buyer beware situation. Specifically: - If you specify only "kgdboc_earlycon" but not "kgdboc" then (depending on your serial driver) things will probably work OK, but you'll get a warning printed the first time you use kgdb after the boot console is gone. You'd only be able to do this, of course, if the serial driver you're running atop provided an early boot console. - If your "kgdboc_earlycon" and "kgdboc" devices are not the same device things should work OK, but it'll be your job to switch over which device you're monitoring (including figuring out how to switch over gdb in-flight if you're using it). When trying to enable "kgdboc_earlycon" it should be noted that the names that are registered through the boot console layer and the tty layer are not the same for the same port. For example when debugging on one board I'd need to pass "kgdboc_earlycon=qcom_geni kgdboc=ttyMSM0" to enable things properly. Since digging up the boot console name is a pain and there will rarely be more than one boot console enabled, you can provide the "kgdboc_earlycon" parameter without specifying the name of the boot console. In this case we'll just pick the first boot that implements read() that we find. This new "kgdboc_earlycon" parameter should be contrasted to the existing "ekgdboc" parameter. While both provide a way to debug very early, the usage and mechanisms are quite different. Specifically "kgdboc_earlycon" is meant to be used in tandem with "kgdboc" and there is a transition from one to the other. The "ekgdboc" parameter, on the other hand, replaces the "kgdboc" parameter. It runs the same logic as the "kgdboc" parameter but just relies on your TTY driver being present super early. The only known usage of the old "ekgdboc" parameter is documented as "ekgdboc=kbd earlyprintk=vga". It should be noted that "kbd" has special treatment allowing it to init early as a tty device. Signed-off-by: Douglas Anderson Reviewed-by: Greg Kroah-Hartman Tested-by: Sumit Garg Link: https://lore.kernel.org/r/20200507130644.v4.8.I8fba5961bf452ab92350654aa61957f23ecf0100@changeid Signed-off-by: Daniel Thompson

kgdb: Return true in kgdb_nmi_poll_knock()

2020-05-07T14:20:55+00:00

Fix the following coccicheck warning: include/linux/kgdb.h:301:54-55: WARNING: return of 0/1 in function 'kgdb_nmi_poll_knock' with return type bool Signed-off-by: Jason Yan Link: https://lore.kernel.org/r/20200507110649.37426-1-yanaijie@huawei.com Signed-off-by: Daniel Thompson