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[73.78.62.130]) by smtp.googlemail.com with ESMTPSA id e32-20020a026d60000000b0039e583abceasm6497289jaf.68.2023.01.13.11.31.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jan 2023 11:31:03 -0800 (PST) From: Jim Cromie To: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Cc: jani.nikula@intel.com, ville.syrjala@linux.intel.com, daniel.vetter@ffwll.ch, seanpaul@chromium.org, robdclark@gmail.com, jbaron@akamai.com, gregkh@linuxfoundation.org, Jim Cromie , Peter Zijlstra Subject: [PATCH v2 20/20] jump_label: RFC - tolerate toggled state Date: Fri, 13 Jan 2023 12:30:16 -0700 Message-Id: <20230113193016.749791-21-jim.cromie@gmail.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230113193016.749791-1-jim.cromie@gmail.com> References: <20230113193016.749791-1-jim.cromie@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754937636379715993?= X-GMAIL-MSGID: =?utf-8?q?1754937636379715993?= __jump_label_patch currently will "crash the box" if it finds a jump_entry not as expected. ISTM this overly harsh; it doesn't distinguish between "alternate/opposite" state, and truly "insane/corrupted". The "opposite" (but well-formed) state is a milder mis-initialization problem, and some less severe mitigation seems practical. ATM this just warns about it; a range/enum of outcomes: warn, crash, silence, ok, fixup-continue, etc, are possible on a case-by-case basis. Ive managed to create this mis-initialization condition with test_dynamic_debug.ko & _submod.ko. These replicate DRM's regression on DRM_USE_DYNAMIC_DEBUG=y; drm.debug callsites in drivers/helpers (dependent modules) are not enabled along with those in drm.ko itself. Heres that "opposite" state, occurring: :#> echo 1 > /sys/module/test_dynamic_debug/parameters/p_disjoint_bits [ 235.258452] dyndbg: bits:0x1 > *.p_disjoint_bits [ 235.258908] dyndbg: apply bitmap: 0x1 to: 0x4f for '*' [ 235.259351] dyndbg: query 0: "class D2_DRIVER -p" mod:* [ 235.259799] dyndbg: split into words: "class" "D2_DRIVER" "-p" [ 235.260290] dyndbg: op='-' flags=0x0 maskp=0xfffffffe [ 235.260720] dyndbg: parsed: func="" file="" module="" format="" lineno=0-0 class=D2_DRIVER [ 235.261418] dyndbg: good-class: test_dynamic_debug.D2_DRIVER module: test_dynamic_debug nd: 32 nc: 4 nu: 0 [ 235.262276] dyndbg: class-ref: test_dynamic_debug_submod.D2_DRIVER module: test_dynamic_debug_submod nd: 32 nc: 0 nu: 4 [ 235.263178] jump_label: found alternate op at do_cats+0x16/0x180 [test_dynamic_debug_submod] [00000000ba944cc2] (0f 1f 44 00 00 != e9 e1 00 00 00)) size:5 type:0 [ 235.264431] dyndbg: processed 1 queries, with 2 matches, 0 errs [ 235.264951] dyndbg: bit_1: 2 matches on class: D2_DRIVER -> 0x1 [ 235.265444] dyndbg: query 0: "class D2_KMS -p" mod:* [ 235.265869] dyndbg: split into words: "class" "D2_KMS" "-p" [ 235.266337] dyndbg: op='-' flags=0x0 maskp=0xfffffffe [ 235.266767] dyndbg: parsed: func="" file="" module="" format="" lineno=0-0 class=D2_KMS [ 235.267432] dyndbg: good-class: test_dynamic_debug.D2_KMS module: test_dynamic_debug nd: 32 nc: 4 nu: 0 [ 235.268264] dyndbg: class-ref: test_dynamic_debug_submod.D2_KMS module: test_dynamic_debug_submod nd: 32 nc: 0 nu: 4 [ 235.269142] jump_label: found alternate op at do_cats+0x1b/0x180 [test_dynamic_debug_submod] [00000000e8d6c160] (0f 1f 44 00 00 != e9 c4 00 00 00)) size:5 type:0 [ 235.270384] dyndbg: processed 1 queries, with 2 matches, 0 errs RFC: Ive hit this case a few times, but havent been able to isolate the when and why. warn-only is something of a punt, and I'm still left with remaining bugs which are likely related; I'm able to toggle the p-flag on callsites in the submod, but their enablement still doesn't yield logging activity. CC: Jason Baron CC: Peter Zijlstra Signed-off-by: Jim Cromie --- heres the Fatal kernel bug: (its on a -dirty kernel) [ 2831.639643] dyndbg: good-class: test_dynamic_debug.D2_CORE module: test_dynamic_debug nd: 32 nc: 4 nu: 0 [ 2831.641316] dyndbg: class-ref: test_dynamic_debug_submod.D2_CORE module: test_dynamic_debug_submod nd: 32 nc: 0 nu: 4 [ 2831.642048] jump_label: Fatal kernel bug, unexpected op at do_cats+0x11/0x180 [test_dynamic_debug_submod] [00000000fa724232] (0f 1f 44 00 00 != e9 fe 00 00 00)) size:5 type:0 [ 2831.643077] ------------[ cut here ]------------ [ 2831.643537] kernel BUG at arch/x86/kernel/jump_label.c:73! [ 2831.643902] invalid opcode: 0000 [#1] PREEMPT SMP KASAN [ 2831.644248] CPU: 1 PID: 425 Comm: bash Tainted: G E 6.1.0-tf2-00021-gbe37efe8728f-dirty #696 [ 2831.644862] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 [ 2831.645431] RIP: 0010:__jump_label_patch.cold+0x24/0x26 [ 2831.645773] Code: 83 e9 ef 00 ac fe 48 c7 c3 20 4c 5c 85 41 56 45 89 f9 49 89 d8 4c 89 e9 4c 89 ea 4c 89 ee 48 c7 c7 00 70 c5 82 e8 d7 1a 01 00 <0f> 0b 41 54 45 31 e4 55 48 89 fd 53 bb 00 00 00 80 48 81 c3 00 20 [ 2831.646896] RSP: 0018:ffffc9000101f738 EFLAGS: 00010282 [ 2831.647242] RAX: 00000000000000a2 RBX: ffffffff855c4c20 RCX: 0000000000000000 [ 2831.647702] RDX: 00000000000000a2 RSI: ffffffff81294fc4 RDI: fffff52000203ede [ 2831.648155] RBP: ffffc9000101f778 R08: 0000000000000003 R09: ffffc9000101f4ff [ 2831.648626] R10: fffff52000203e9f R11: 78656e75202c756a R12: ffffffff855c4c20 [ 2831.649096] R13: ffffffffc0250011 R14: 0000000000000000 R15: 0000000000000005 [ 2831.649498] FS: 00007fe4014aa740(0000) GS:ffff88805ae00000(0000) knlGS:0000000000000000 [ 2831.649894] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2831.650175] CR2: 00007f9c326e6c08 CR3: 000000000ff59000 CR4: 0000000000750ee0 [ 2831.650520] PKRU: 55555554 [ 2831.650667] Call Trace: [ 2831.650793] [ 2831.650903] ? do_cats+0x11/0x180 [test_dynamic_debug_submod] [ 2831.651195] arch_jump_label_transform_queue+0x43/0xa0 [ 2831.651450] __jump_label_update+0x9b/0x1b0 [ 2831.651670] static_key_disable_cpuslocked+0x9f/0xd0 [ 2831.651917] static_key_disable+0x16/0x20 [ 2831.652117] ddebug_change+0x45d/0x5c0 --- arch/x86/kernel/jump_label.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index f5b8ef02d172..9175f7e8c267 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -35,7 +35,7 @@ struct jump_label_patch { static struct jump_label_patch __jump_label_patch(struct jump_entry *entry, enum jump_label_type type) { - const void *expect, *code, *nop; + const void *expect, *code, *nop, *alt; const void *addr, *dest; int size; @@ -57,20 +57,28 @@ __jump_label_patch(struct jump_entry *entry, enum jump_label_type type) default: BUG(); } - if (type == JUMP_LABEL_JMP) + if (type == JUMP_LABEL_JMP) { expect = nop; - else + alt = code; + } else { expect = code; - + alt = nop; + } if (memcmp(addr, expect, size)) { /* - * The location is not an op that we were expecting. - * Something went wrong. Crash the box, as something could be - * corrupting the kernel. + * The location is not the op that we were expecting. + * If its the alternate/toggled op, then warn, otherwise + * something went more wrong. Crash the box, as + * something could be corrupting the kernel. */ - pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n", + if (memcmp(addr, alt, size)) { + pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n", + addr, addr, addr, expect, size, type); + BUG(); + } else { + pr_warn("jump_label: found alternate op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n", addr, addr, addr, expect, size, type); - BUG(); + } } if (type == JUMP_LABEL_NOP)