pm24.git/kernel/debug, branch v5.2-rc1

kdb: Fix bound check compiler warning

2019-05-14T12:44:24Z

The strncpy() function may leave the destination string buffer unterminated, better use strscpy() instead. This fixes the following warning with gcc 8.2: kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr': kernel/debug/kdb/kdb_io.c:449:3: warning: 'strncpy' specified bound 256 equals destination size [-Wstringop-truncation] strncpy(kdb_prompt_str, prompt, CMD_BUFLEN); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Signed-off-by: Wenlin Kang Signed-off-by: Daniel Thompson

kdb: do a sanity check on the cpu in kdb_per_cpu()

2019-05-12T08:50:44Z

The "whichcpu" comes from argv[3]. The cpu_online() macro looks up the cpu in a bitmap of online cpus, but if the value is too high then it could read beyond the end of the bitmap and possibly Oops. Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)") Signed-off-by: Dan Carpenter Reviewed-by: Douglas Anderson Signed-off-by: Daniel Thompson

kdb: Get rid of broken attempt to print CCVERSION in kdb summary

2019-05-12T08:50:43Z

If you drop into kdb and type "summary", it prints out a line that says this: ccversion CCVERSION ...and I don't mean that it actually prints out the version of the C compiler. It literally prints out the string "CCVERSION". The version of the C Compiler is already printed at boot up and it doesn't seem useful to replicate this in kdb. Let's just delete it. We can also delete the bit of the Makefile that called the C compiler in an attempt to pass this into kdb. This will remove one extra call to the C compiler at Makefile parse time and (very slightly) speed up builds. Signed-off-by: Douglas Anderson Reviewed-by: Masahiro Yamada Signed-off-by: Daniel Thompson

kdb: kdb_support: replace strcpy() by strscpy()

2019-05-02T12:42:01Z

The strcpy() function is being deprecated. Replace it by the safer strscpy() and fix the following Coverity warning: "You might overrun the 129-character fixed-size string ks_namebuf by copying name without checking the length." Addresses-Coverity-ID: 138995 ("Copy into fixed size buffer") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Daniel Thompson

gdbstub: Replace strcpy() by strscpy()

2019-05-02T12:40:27Z

The strcpy() function is being deprecated. Replace it by the safer strscpy() and fix the following Coverity warning: "You might overrun the 1024-character fixed-size string remcom_in_buffer by copying cmd without checking the length." Addresses-Coverity-ID: 138999 ("Copy into fixed size buffer") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Daniel Thompson

gdbstub: mark expected switch fall-throughs

2019-05-02T12:38:04Z

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where we are expecting to fall through. This patch fixes the following warnings: kernel/debug/gdbstub.c: In function ‘gdb_serial_stub’: kernel/debug/gdbstub.c:1031:7: warning: this statement may fall through [-Wimplicit-fallthrough=] if (remcom_in_buffer[1] == '\0') { ^ kernel/debug/gdbstub.c:1036:3: note: here case 'C': /* Exception passing */ ^~~~ kernel/debug/gdbstub.c:1040:7: warning: this statement may fall through [-Wimplicit-fallthrough=] if (tmp == 0) ^ kernel/debug/gdbstub.c:1043:3: note: here case 'c': /* Continue packet */ ^~~~ kernel/debug/gdbstub.c:1050:4: warning: this statement may fall through [-Wimplicit-fallthrough=] dbg_activate_sw_breakpoints(); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ kernel/debug/gdbstub.c:1052:3: note: here default: ^~~~~~~ Warning level 3 was used: -Wimplicit-fallthrough=3 Notice that, in this particular case, the code comment is modified in accordance with what GCC is expecting to find. This patch is part of the ongoing efforts to enable -Wimplicit-fallthrough. Signed-off-by: Gustavo A. R. Silva Acked-by: Jason Wessel Signed-off-by: Daniel Thompson

kdb: use bool for binary state indicators

2018-12-30T08:31:52Z

defcmd_in_progress is the state trace for command group processing - within a command group or not - usable is an indicator if a command set is valid (allocated/non-empty) - so use a bool for those binary indication here. Signed-off-by: Nicholas Mc Guire Reviewed-by: Daniel Thompson Signed-off-by: Daniel Thompson

kdb: Don't back trace on a cpu that didn't round up

2018-12-30T08:31:23Z

If you have a CPU that fails to round up and then run 'btc' you'll end up crashing in kdb becaue we dereferenced NULL. Let's add a check. It's wise to also set the task to NULL when leaving the debugger so that if we fail to round up on a later entry into the debugger we won't backtrace a stale task. Signed-off-by: Douglas Anderson Acked-by: Daniel Thompson Signed-off-by: Daniel Thompson

kgdb: Don't round up a CPU that failed rounding up before

2018-12-30T08:29:13Z

If we're using the default implementation of kgdb_roundup_cpus() that uses smp_call_function_single_async() we can end up hanging kgdb_roundup_cpus() if we try to round up a CPU that failed to round up before. Specifically smp_call_function_single_async() will try to wait on the csd lock for the CPU that we're trying to round up. If the previous round up never finished then that lock could still be held and we'll just sit there hanging. There's not a lot of use trying to round up a CPU that failed to round up before. Let's keep a flag that indicates whether the CPU started but didn't finish to round up before. If we see that flag set then we'll skip the next round up. In general we have a few goals here: - We never want to end up calling smp_call_function_single_async() when the csd is still locked. This is accomplished because flush_smp_call_function_queue() unlocks the csd _before_ invoking the callback. That means that when kgdb_nmicallback() runs we know for sure the the csd is no longer locked. Thus when we set "rounding_up = false" we know for sure that the csd is unlocked. - If there are no timeouts rounding up we should never skip a round up. NOTE #1: In general trying to continue running after failing to round up CPUs doesn't appear to be supported in the debugger. When I simulate this I find that kdb reports "Catastrophic error detected" when I try to continue. I can overrule and continue anyway, but it should be noted that we may be entering the land of dragons here. Possibly the "Catastrophic error detected" was added _because_ of the future failure to round up, but even so this is an area of the code that hasn't been strongly tested. NOTE #2: I did a bit of testing before and after this change. I introduced a 10 second hang in the kernel while holding a spinlock that I could invoke on a certain CPU with 'taskset -c 3 cat /sys/...". Before this change if I did: - Invoke hang - Enter debugger - g (which warns about Catastrophic error, g again to go anyway) - g - Enter debugger ...I'd hang the rest of the 10 seconds without getting a debugger prompt. After this change I end up in the debugger the 2nd time after only 1 second with the standard warning about 'Timed out waiting for secondary CPUs.' I'll also note that once the CPU finished waiting I could actually debug it (aka "btc" worked) I won't promise that everything works perfectly if the errant CPU comes back at just the wrong time (like as we're entering or exiting the debugger) but it certainly seems like an improvement. NOTE #3: setting 'kgdb_info[cpu].rounding_up = false' is in kgdb_nmicallback() instead of kgdb_call_nmi_hook() because some implementations override kgdb_call_nmi_hook(). It shouldn't hurt to have it in kgdb_nmicallback() in any case. NOTE #4: this logic is really only needed because there is no API call like "smp_try_call_function_single_async()" or "smp_csd_is_locked()". If such an API existed then we'd use it instead, but it seemed a bit much to add an API like this just for kgdb. Signed-off-by: Douglas Anderson Acked-by: Daniel Thompson Signed-off-by: Daniel Thompson

kgdb: Fix kgdb_roundup_cpus() for arches who used smp_call_function()

2018-12-30T08:28:02Z

When I had lockdep turned on and dropped into kgdb I got a nice splat on my system. Specifically it hit: DEBUG_LOCKS_WARN_ON(current->hardirq_context) Specifically it looked like this: sysrq: SysRq : DEBUG ------------[ cut here ]------------ DEBUG_LOCKS_WARN_ON(current->hardirq_context) WARNING: CPU: 0 PID: 0 at .../kernel/locking/lockdep.c:2875 lockdep_hardirqs_on+0xf0/0x160 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0 #27 pstate: 604003c9 (nZCv DAIF +PAN -UAO) pc : lockdep_hardirqs_on+0xf0/0x160 ... Call trace: lockdep_hardirqs_on+0xf0/0x160 trace_hardirqs_on+0x188/0x1ac kgdb_roundup_cpus+0x14/0x3c kgdb_cpu_enter+0x53c/0x5cc kgdb_handle_exception+0x180/0x1d4 kgdb_compiled_brk_fn+0x30/0x3c brk_handler+0x134/0x178 do_debug_exception+0xfc/0x178 el1_dbg+0x18/0x78 kgdb_breakpoint+0x34/0x58 sysrq_handle_dbg+0x54/0x5c __handle_sysrq+0x114/0x21c handle_sysrq+0x30/0x3c qcom_geni_serial_isr+0x2dc/0x30c ... ... irq event stamp: ...45 hardirqs last enabled at (...44): [...] __do_softirq+0xd8/0x4e4 hardirqs last disabled at (...45): [...] el1_irq+0x74/0x130 softirqs last enabled at (...42): [...] _local_bh_enable+0x2c/0x34 softirqs last disabled at (...43): [...] irq_exit+0xa8/0x100 ---[ end trace adf21f830c46e638 ]--- Looking closely at it, it seems like a really bad idea to be calling local_irq_enable() in kgdb_roundup_cpus(). If nothing else that seems like it could violate spinlock semantics and cause a deadlock. Instead, let's use a private csd alongside smp_call_function_single_async() to round up the other CPUs. Using smp_call_function_single_async() doesn't require interrupts to be enabled so we can remove the offending bit of code. In order to avoid duplicating this across all the architectures that use the default kgdb_roundup_cpus(), we'll add a "weak" implementation to debug_core.c. Looking at all the people who previously had copies of this code, there were a few variants. I've attempted to keep the variants working like they used to. Specifically: * For arch/arc we passed NULL to kgdb_nmicallback() instead of get_irq_regs(). * For arch/mips there was a bit of extra code around kgdb_nmicallback() NOTE: In this patch we will still get into trouble if we try to round up a CPU that failed to round up before. We'll try to round it up again and potentially hang when we try to grab the csd lock. That's not new behavior but we'll still try to do better in a future patch. Suggested-by: Daniel Thompson Signed-off-by: Douglas Anderson Cc: Vineet Gupta Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Richard Kuo Cc: Ralf Baechle Cc: Paul Burton Cc: James Hogan Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Yoshinori Sato Cc: Rich Felker Cc: "David S. Miller" Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Acked-by: Will Deacon Signed-off-by: Daniel Thompson