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Booting one of my machines, it triggered the following crash: Kernel/User page tables isolation: enabled ftrace: allocating 36577 entries in 143 pages Starting tracer 'function' BUG: unable to handle page fault for address: ffffffffa000005c #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 2014067 P4D 2014067 PUD2015063PMD 7b253067 PTE7b252061Oops: 0003 [#1] PREEMPT SMP PTI CPU: 0 PID: 0 Comm: swapper Not tainted 5.4.0-test+ #24 Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007 RIP: 0010:text_poke_early+0x4a/0x58 Code: 34 24 48 89 54 24 08 e8 bf 72 0b 00 48 8b 34 24 48 8b 4c 24 08 84 c0 74 0b 48 89 df f3 a4 48 83 c4 10 5b c3 9c 58 fa 48 89 df <f3> a4 50 9d 48 83 c4 10 5b e9 d6 f9 ff ff 0 41 57 49 RSP: 0000:ffffffff82003d38 EFLAGS: 00010046 RAX: 0000000000000046 RBX: ffffffffa000005c RCX: 0000000000000005 RDX: 0000000000000005 RSI: ffffffff825b9a90 RDI: ffffffffa000005c RBP: ffffffffa000005c R08: 0000000000000000 R09: ffffffff8206e6e0 R10: ffff88807b01f4c0 R11: ffffffff8176c106 R12: ffffffff8206e6e0 R13: ffffffff824f2440 R14: 0000000000000000 R15: ffffffff8206eac0 FS: 0000000000000000(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffa000005c CR3: 0000000002012000 CR4: 00000000000006b0 Call Trace: text_poke_bp+0x27/0x64 ? mutex_lock+0x36/0x5d arch_ftrace_update_trampoline+0x287/0x2d5 ? ftrace_replace_code+0x14b/0x160 ? ftrace_update_ftrace_func+0x65/0x6c __register_ftrace_function+0x6d/0x81 ftrace_startup+0x23/0xc1 register_ftrace_function+0x20/0x37 func_set_flag+0x59/0x77 __set_tracer_option.isra.19+0x20/0x3e trace_set_options+0xd6/0x13e apply_trace_boot_options+0x44/0x6d register_tracer+0x19e/0x1ac early_trace_init+0x21b/0x2c9 start_kernel+0x241/0x518 ? load_ucode_intel_bsp+0x21/0x52 secondary_startup_64+0xa4/0xb0 I was able to trigger it on other machines, when I added to the kernel command line of both "ftrace=function" and "trace_options=func_stack_trace". The cause is the "ftrace=function" would register the function tracer and create a trampoline, and it will set it as executable and read-only. Then the "trace_options=func_stack_trace" would then update the same trampoline to include the stack tracer version of the function tracer. But since the trampoline already exists, it updates it with text_poke_bp(). The problem is that text_poke_bp() called while system_state == SYSTEM_BOOTING, it will simply do a memcpy() and not the page mapping, as it would think that the text is still read-write. But in this case it is not, and we take a fault and crash. Instead, lets keep the ftrace trampolines read-write during boot up, and then when the kernel executable text is set to read-only, the ftrace trampolines get set to read-only as well. Link: https://lkml.kernel.org/r/20200430202147.4dc6e2de@oasis.local.home Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: stable@vger.kernel.org Fixes:768ae4406a("x86/ftrace: Use text_poke()") Acked-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
54 lines
1.5 KiB
C
54 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_KERNEL_FTRACE_INTERNAL_H
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#define _LINUX_KERNEL_FTRACE_INTERNAL_H
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#ifdef CONFIG_FUNCTION_TRACER
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extern struct mutex ftrace_lock;
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extern struct ftrace_ops global_ops;
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#ifdef CONFIG_DYNAMIC_FTRACE
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int ftrace_startup(struct ftrace_ops *ops, int command);
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int ftrace_shutdown(struct ftrace_ops *ops, int command);
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int ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs);
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#else /* !CONFIG_DYNAMIC_FTRACE */
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int __register_ftrace_function(struct ftrace_ops *ops);
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int __unregister_ftrace_function(struct ftrace_ops *ops);
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/* Keep as macros so we do not need to define the commands */
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# define ftrace_startup(ops, command) \
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({ \
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int ___ret = __register_ftrace_function(ops); \
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if (!___ret) \
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(ops)->flags |= FTRACE_OPS_FL_ENABLED; \
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___ret; \
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})
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# define ftrace_shutdown(ops, command) \
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({ \
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int ___ret = __unregister_ftrace_function(ops); \
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if (!___ret) \
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(ops)->flags &= ~FTRACE_OPS_FL_ENABLED; \
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___ret; \
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})
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static inline int
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ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
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{
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return 1;
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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extern int ftrace_graph_active;
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void update_function_graph_func(void);
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#else /* !CONFIG_FUNCTION_GRAPH_TRACER */
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# define ftrace_graph_active 0
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static inline void update_function_graph_func(void) { }
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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#else /* !CONFIG_FUNCTION_TRACER */
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#endif /* CONFIG_FUNCTION_TRACER */
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#endif
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