On Sat, Jul 1, 2023 at 12:22 PM Guo Ren <guoren@xxxxxxxxxx> wrote: > > On Sat, Jul 1, 2023 at 11:08 AM Guo Ren <guoren@xxxxxxxxxx> wrote: > > > > On Sat, Jul 1, 2023 at 10:55 AM Guo Ren <guoren@xxxxxxxxxx> wrote: > > > > > > On Fri, Jun 30, 2023 at 10:51 PM Daniel Thompson > > > <daniel.thompson@xxxxxxxxxx> wrote: > > > > > > > > On Fri, Jun 30, 2023 at 07:22:40AM -0400, Guo Ren wrote: > > > > > On Fri, Jun 30, 2023 at 7:16 AM Guo Ren <guoren@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Thu, Jun 29, 2023 at 10:02 AM Daniel Thompson > > > > > > <daniel.thompson@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > On Tue, Feb 21, 2023 at 10:30:18PM -0500, guoren@xxxxxxxxxx wrote: > > > > > > > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > > > > > > > > > > > > > > > This patch converts riscv to use the generic entry infrastructure from > > > > > > > > kernel/entry/*. The generic entry makes maintainers' work easier and > > > > > > > > codes more elegant. Here are the changes: > > > > > > > > > > > > > > > > - More clear entry.S with handle_exception and ret_from_exception > > > > > > > > - Get rid of complex custom signal implementation > > > > > > > > - Move syscall procedure from assembly to C, which is much more > > > > > > > > readable. > > > > > > > > - Connect ret_from_fork & ret_from_kernel_thread to generic entry. > > > > > > > > - Wrap with irqentry_enter/exit and syscall_enter/exit_from_user_mode > > > > > > > > - Use the standard preemption code instead of custom > > > > > > > > > > > > > > > > Suggested-by: Huacai Chen <chenhuacai@xxxxxxxxxx> > > > > > > > > Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx> > > > > > > > > Tested-by: Yipeng Zou <zouyipeng@xxxxxxxxxx> > > > > > > > > Tested-by: Jisheng Zhang <jszhang@xxxxxxxxxx> > > > > > > > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > > > > > > > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx> > > > > > > > > Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx> > > > > > > > > > > > > > > Apologies for the late feedback but I've been swamped lately and only > > > > > > > recently got round to running the full kgdb test suite on the v6.4 > > > > > > > series. > > > > > > > > > > > > > > The kgdb test suite includes a couple of tests that verify that the > > > > > > > system resumes after breakpointing due to a BUG(): > > > > > > > https://github.com/daniel-thompson/kgdbtest/blob/master/tests/test_kdb_fault_injection.py#L24-L45 > > > > > > > > > > > > > > These tests have regressed on riscv between v6.3 and v6.4 and a bisect > > > > > > > is pointing at this patch. With these changes in place then, after kdb > > > > > > > resumes the system, the BUG() message is printed as normal but then > > > > > > > immediately fails. From the backtrace it looks like the new entry/exit > > > > > > > code cannot advance past a compiled breakpoint instruction: > > > > > > > ~~~ > > > > > > > PANIC: Fatal exception in interrupt > > > > > > It comes from: > > > > > > void die(struct pt_regs *regs, ... > > > > > > { > > > > > > ... > > > > > > if (in_interrupt()) > > > > > > panic("Fatal exception in interrupt"); > > > > > > ... > > > > > > > > > > > > We could add a dump_backtrace to see what happened: > > > > > > if (in_interrupt()) { > > > > > > + dump_backtrace(regs, NULL, KERN_DEFAULT); > > > > > Sorry, it should be: > > > > > + dump_backtrace(NULL, NULL, KERN_DEFAULT); > > > > > We need current stack info, not exception context. > > > > > > > > I added this... and I also stopped kgdb from intercepting the panic() > > > > since that interferes with the console output from dump_backtrace(). > > > > > > > > ~~~ > > > > # /bin/echo BUG > /sys/kernel/debug/provoke-crash/DIRECT > > > > [ 3.380565] lkdtm: Performing direct entry BUG > > > > > > > > Entering kdb (current=0xff6000000380ab00, pid 98) on processor 0 due to NonMaskable Interrupt @ 0xffffffff8064b844 > > > > kdb> go > > > > Catastrophic error detected > > > > kdb_continue_catastrophic=0, type go a second time if you really want to continue > > > > kdb> go > > > > Catastrophic error detected > > > > kdb_continue_catastrophic=0, attempting to continue > > > > [ 3.381411] ------------[ cut here ]------------ > > > > [ 3.381454] kernel BUG at drivers/misc/lkdtm/bugs.c:78! > > > > [ 3.381609] Kernel BUG [#1] > > > > [ 3.381632] Modules linked in: > > > > [ 3.381734] CPU: 0 PID: 98 Comm: echo Not tainted 6.4.0-rc6-00004-ge6e9d4598760-dirty #126 > > > > [ 3.381817] Hardware name: riscv-virtio,qemu (DT) > > > > [ 3.381885] epc : lkdtm_BUG+0x6/0x8 > > > > [ 3.381959] ra : lkdtm_do_action+0x10/0x1c > > > > [ 3.381978] epc : ffffffff8064b844 ra : ffffffff8064afb4 sp : ff200000008c3d30 > > > > [ 3.381991] gp : ffffffff810665a0 tp : ff6000000380ab00 t0 : 6500000000000000 > > > > [ 3.382002] t1 : 0000000000000001 t2 : 6550203a6d74646b s0 : ff200000008c3d40 > > > > [ 3.382012] s1 : ff60000003988000 a0 : ffffffff80fc0260 a1 : ff6000003ffad788 > > > > [ 3.382023] a2 : ff6000003ffb9530 a3 : 0000000000000000 a4 : 0000000000000000 > > > > [ 3.382034] a5 : ffffffff8064b83e a6 : 0000000000000050 a7 : 0000000000040000 > > > > [ 3.382045] s2 : 0000000000000004 s3 : ffffffff80fc0260 s4 : ff200000008c3e70 > > > > [ 3.382056] s5 : ff600000033223a8 s6 : 00000000000f0cc0 s7 : ff60000002211000 > > > > [ 3.382066] s8 : 00ffffffafc50c08 s9 : 00ffffffafc4b9b8 s10: 0000000000000000 > > > > [ 3.382077] s11: 0000000000000001 t3 : 461f715700000000 t4 : 0000000000000002 > > > > [ 3.382087] t5 : 0000000000000000 t6 : ff200000008c3b58 > > > > [ 3.382097] status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003 > > > > [ 3.382139] [<ffffffff8064b844>] lkdtm_BUG+0x6/0x8 > > > > [ 3.382245] Code: 0513 9245 b097 0039 80e7 7f20 bf39 1141 e422 0800 (9002) 1141 > > > > [ 3.594697] ---[ end trace 0000000000000000 ]--- > > > > > > > > At this point we expect a shell prompt since we should have taken the BUG(), > > > > killed the echo process and returned to the shell. However in v6.4 we get the > > > > following instead (including the instrumentation you asked for): > > > > > > After comparing with arm64, I found that arm64 uses spinlock_irq to > > > protect the in_interrupt(). I think this would make in_interrupt() = > > > 0. > > > > > > So how about trying: > > > > > > diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > > > index 5158961ea977..0ac914a99ee3 100644 > > > --- a/arch/riscv/kernel/traps.c > > > +++ b/arch/riscv/kernel/traps.c > > > @@ -82,13 +82,15 @@ void die(struct pt_regs *regs, const char *str) > > > > > > bust_spinlocks(0); > > > add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE); > > > - spin_unlock_irqrestore(&die_lock, flags); > > > oops_exit(); > > > > > > if (in_interrupt()) > > > panic("Fatal exception in interrupt"); > > > if (panic_on_oops) > > > panic("Fatal exception"); > > > + > > > + spin_unlock_irqrestore(&die_lock, flags); > > En... It seems it's not correct, how can I reproduce your environment > > on qemu? Sorry, I'm not familiar with kgdb. > > I got it: > Normal is: > # mount -t debugfs none /sys/kernel/debug/ > # /bin/echo BUG > /sys/kernel/debug/provoke-crash/DIRECT > [ 8.948041] lkdtm: Performing direct entry BUG > [ 8.949228] ------------[ cut here ]------------ > [ 8.949640] kernel BUG at drivers/misc/lkdtm/bugs.c:78! > [ 8.950534] Kernel BUG [#1] > [ 8.950944] Modules linked in: > [ 8.951805] CPU: 0 PID: 106 Comm: echo Not tainted > 6.3.0-rc2-00295-gb4e5219985e8 #22 > [ 8.952831] Hardware name: riscv-virtio,qemu (DT) > [ 8.953587] epc : lkdtm_BUG+0x6/0x8 > [ 8.954232] ra : lkdtm_do_action+0x14/0x1c > [ 8.954713] epc : ffffffff805549e2 ra : ffffffff8087245c sp : > ff2000000081bd60 > [ 8.955378] gp : ffffffff814ffec0 tp : ff600000023c8000 t0 : > 6500000000000000 > [ 8.956029] t1 : 000000000000006c t2 : 6550203a6d74646b s0 : > ff2000000081bd70 > [ 8.956699] s1 : ffffffff814bee50 a0 : ffffffff814bee50 a1 : > ff6000001fbd8608 > [ 8.957381] a2 : ff6000001fbdb868 a3 : 0000000000000000 a4 : > 0000000000000000 > [ 8.958035] a5 : ffffffff805549dc a6 : 0000000000000032 a7 : > 0000000000000038 > [ 8.958708] s2 : 0000000000000004 s3 : 00000000556371a0 s4 : > ff2000000081be90 > [ 8.959397] s5 : ff60000001c90000 s6 : 00000000556371a0 s7 : > 0000000000000030 > [ 8.960053] s8 : 000000007fffec78 s9 : 0000000000000007 s10: > 0000000055637480 > [ 8.960717] s11: 0000000000000001 t3 : ffffffff81512e97 t4 : > ffffffff81512e97 > [ 8.961379] t5 : ffffffff81512e98 t6 : ff2000000081bba8 > [ 8.961888] status: 0000000100000120 badaddr: 0000000000000000 > cause: 0000000000000003 > [ 8.962923] [<ffffffff805549e2>] lkdtm_BUG+0x6/0x8 > [ 8.964194] Code: 0513 d665 7097 0031 80e7 f000 b705 1141 e422 0800 > (9002) 1141 > [ 8.965847] ---[ end trace 0000000000000000 ]--- > [ 8.966637] note: echo[106] exited with irqs disabled > Segmentation fault > # > > After generic_entry: > # mount -t debugfs none /sys/kernel/debug/ > # /bin/echo BUG > /sys/kernel/debug/provoke-crash/DIRECT > [ 8.152247] lkdtm: Performing direct entry BUG > [ 8.153652] ------------[ cut here ]------------ > [ 8.153825] kernel BUG at drivers/misc/lkdtm/bugs.c:78! > [ 8.154341] Kernel BUG [#1] > [ 8.154440] Modules linked in: > [ 8.154918] CPU: 0 PID: 106 Comm: echo Not tainted > 6.4.0-rc1-00055-g0ca05a4b079f #21 > [ 8.155301] Hardware name: riscv-virtio,qemu (DT) > [ 8.155581] epc : lkdtm_BUG+0x6/0x8 > [ 8.155880] ra : lkdtm_do_action+0x14/0x1c > [ 8.155977] epc : ffffffff8059d4b4 ra : ffffffff808c1a84 sp : > ff2000000081bd40 > [ 8.156030] gp : ffffffff81503c08 tp : ff600000028ebac0 t0 : > 6500000000000000 > [ 8.156079] t1 : 000000000000006c t2 : 6550203a6d74646b s0 : > ff2000000081bd50 > [ 8.156144] s1 : ffffffff814c2e88 a0 : ffffffff814c2e88 a1 : > ff6000001ffd8608 > [ 8.156193] a2 : ff6000001ffdb870 a3 : 0000000000000000 a4 : > 0000000000000000 > [ 8.156241] a5 : ffffffff8059d4ae a6 : 0000000000000032 a7 : > 0000000000000038 > [ 8.156288] s2 : 0000000000000004 s3 : 00000000556371a0 s4 : > ff2000000081be70 > [ 8.156335] s5 : ff60000002090000 s6 : 00000000556371a0 s7 : > 0000000000000030 > [ 8.156382] s8 : 000000007fffec78 s9 : 0000000000000007 s10: > 0000000055637480 > [ 8.156428] s11: 0000000000000001 t3 : ffffffff815173d7 t4 : > ffffffff815173d7 > [ 8.156473] t5 : ffffffff815173d8 t6 : ff2000000081bb88 > [ 8.156516] status: 0000000100000120 badaddr: 0000000000000000 > cause: 0000000000000003 > [ 8.156830] [<ffffffff8059d4b4>] lkdtm_BUG+0x6/0x8 > [ 8.157630] Code: 0513 1745 d097 0031 80e7 70a0 b705 1141 e422 0800 > (9002) 1141 > [ 8.169646] ---[ end trace 0000000000000000 ]--- > [ 8.170148] Kernel panic - not syncing: Fatal exception in interrupt > [ 8.171839] ---[ end Kernel panic - not syncing: Fatal exception in > interrupt ]--- > > I'm debugging on it, and soon give the patch. Thx, Daniel, for the report; here is the fixup: https://lore.kernel.org/linux-riscv/20230702025708.784106-1-guoren@xxxxxxxxxx/ I've tested, and it's okay now. # /bin/echo BUG > /sys/kernel/debug/provoke-crash/DIRECT > > > > > > + > > > if (ret != NOTIFY_STOP) > > > make_task_dead(SIGSEGV); > > > } > > > > > > > > > > > [ 3.594801] [<ffffffff80005e3a>] dump_backtrace+0x1c/0x24 > > > > [ 3.594826] [<ffffffff800059f0>] die+0x228/0x238 > > > > [ 3.594835] [<ffffffff80005b38>] handle_break+0x9a/0xe0 > > > > [ 3.594843] [<ffffffff809f30d6>] do_trap_break+0x48/0x5c > > > > [ 3.594854] [<ffffffff80003ee4>] ret_from_exception+0x0/0x64 > > > > [ 3.594862] [<ffffffff8064b844>] lkdtm_BUG+0x6/0x8 > > > > [ 3.594959] Kernel panic - not syncing: Fatal exception in interrupt > > > > [ 3.595005] SMP: stopping secondary CPUs > > > > [ 3.596444] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]--- > > > > ~~~ > > > > > > > > > > > > Daniel. > > > > > > > > > > > > -- > > > Best Regards > > > Guo Ren > > > > > > > > -- > > Best Regards > > Guo Ren > > > > -- > Best Regards > Guo Ren -- Best Regards Guo Ren
