From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- arch/csky/lib/Makefile | 6 ++ arch/csky/lib/delay.c | 39 ++++++++ arch/csky/lib/error-inject.c | 10 ++ arch/csky/lib/string.c | 134 +++++++++++++++++++++++++++ arch/csky/lib/usercopy.c | 214 +++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 403 insertions(+) create mode 100644 arch/csky/lib/Makefile create mode 100644 arch/csky/lib/delay.c create mode 100644 arch/csky/lib/error-inject.c create mode 100644 arch/csky/lib/string.c create mode 100644 arch/csky/lib/usercopy.c (limited to 'arch/csky/lib') diff --git a/arch/csky/lib/Makefile b/arch/csky/lib/Makefile new file mode 100644 index 000000000..d0ce6e2d7 --- /dev/null +++ b/arch/csky/lib/Makefile @@ -0,0 +1,6 @@ +# SPDX-License-Identifier: GPL-2.0-only +lib-y := usercopy.o delay.o +obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o +ifneq ($(CONFIG_HAVE_EFFICIENT_UNALIGNED_STRING_OPS), y) +lib-y += string.o +endif diff --git a/arch/csky/lib/delay.c b/arch/csky/lib/delay.c new file mode 100644 index 000000000..f5db31731 --- /dev/null +++ b/arch/csky/lib/delay.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. +#include +#include +#include +#include + +void __aligned(8) __delay(unsigned long loops) +{ + asm volatile ( + "mov r0, r0\n" + "1:declt %0\n" + "bf 1b" + : "=r"(loops) + : "0"(loops)); +} +EXPORT_SYMBOL(__delay); + +void __const_udelay(unsigned long xloops) +{ + unsigned long long loops; + + loops = (unsigned long long)xloops * loops_per_jiffy * HZ; + + __delay(loops >> 32); +} +EXPORT_SYMBOL(__const_udelay); + +void __udelay(unsigned long usecs) +{ + __const_udelay(usecs * 0x10C7UL); /* 2**32 / 1000000 (rounded up) */ +} +EXPORT_SYMBOL(__udelay); + +void __ndelay(unsigned long nsecs) +{ + __const_udelay(nsecs * 0x5UL); /* 2**32 / 1000000000 (rounded up) */ +} +EXPORT_SYMBOL(__ndelay); diff --git a/arch/csky/lib/error-inject.c b/arch/csky/lib/error-inject.c new file mode 100644 index 000000000..c15fb36fe --- /dev/null +++ b/arch/csky/lib/error-inject.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include + +void override_function_with_return(struct pt_regs *regs) +{ + instruction_pointer_set(regs, regs->lr); +} +NOKPROBE_SYMBOL(override_function_with_return); diff --git a/arch/csky/lib/string.c b/arch/csky/lib/string.c new file mode 100644 index 000000000..d65626fca --- /dev/null +++ b/arch/csky/lib/string.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * String functions optimized for hardware which doesn't + * handle unaligned memory accesses efficiently. + * + * Copyright (C) 2021 Matteo Croce + */ + +#include +#include + +/* Minimum size for a word copy to be convenient */ +#define BYTES_LONG sizeof(long) +#define WORD_MASK (BYTES_LONG - 1) +#define MIN_THRESHOLD (BYTES_LONG * 2) + +/* convenience union to avoid cast between different pointer types */ +union types { + u8 *as_u8; + unsigned long *as_ulong; + uintptr_t as_uptr; +}; + +union const_types { + const u8 *as_u8; + unsigned long *as_ulong; + uintptr_t as_uptr; +}; + +void *memcpy(void *dest, const void *src, size_t count) +{ + union const_types s = { .as_u8 = src }; + union types d = { .as_u8 = dest }; + int distance = 0; + + if (count < MIN_THRESHOLD) + goto copy_remainder; + + /* Copy a byte at time until destination is aligned. */ + for (; d.as_uptr & WORD_MASK; count--) + *d.as_u8++ = *s.as_u8++; + + distance = s.as_uptr & WORD_MASK; + + if (distance) { + unsigned long last, next; + + /* + * s is distance bytes ahead of d, and d just reached + * the alignment boundary. Move s backward to word align it + * and shift data to compensate for distance, in order to do + * word-by-word copy. + */ + s.as_u8 -= distance; + + next = s.as_ulong[0]; + for (; count >= BYTES_LONG; count -= BYTES_LONG) { + last = next; + next = s.as_ulong[1]; + + d.as_ulong[0] = last >> (distance * 8) | + next << ((BYTES_LONG - distance) * 8); + + d.as_ulong++; + s.as_ulong++; + } + + /* Restore s with the original offset. */ + s.as_u8 += distance; + } else { + /* + * If the source and dest lower bits are the same, do a simple + * 32/64 bit wide copy. + */ + for (; count >= BYTES_LONG; count -= BYTES_LONG) + *d.as_ulong++ = *s.as_ulong++; + } + +copy_remainder: + while (count--) + *d.as_u8++ = *s.as_u8++; + + return dest; +} +EXPORT_SYMBOL(memcpy); + +/* + * Simply check if the buffer overlaps an call memcpy() in case, + * otherwise do a simple one byte at time backward copy. + */ +void *memmove(void *dest, const void *src, size_t count) +{ + if (dest < src || src + count <= dest) + return memcpy(dest, src, count); + + if (dest > src) { + const char *s = src + count; + char *tmp = dest + count; + + while (count--) + *--tmp = *--s; + } + return dest; +} +EXPORT_SYMBOL(memmove); + +void *memset(void *s, int c, size_t count) +{ + union types dest = { .as_u8 = s }; + + if (count >= MIN_THRESHOLD) { + unsigned long cu = (unsigned long)c; + + /* Compose an ulong with 'c' repeated 4/8 times */ + cu |= cu << 8; + cu |= cu << 16; + /* Suppress warning on 32 bit machines */ + cu |= (cu << 16) << 16; + + for (; count && dest.as_uptr & WORD_MASK; count--) + *dest.as_u8++ = c; + + /* Copy using the largest size allowed */ + for (; count >= BYTES_LONG; count -= BYTES_LONG) + *dest.as_ulong++ = cu; + } + + /* copy the remainder */ + while (count--) + *dest.as_u8++ = c; + + return s; +} +EXPORT_SYMBOL(memset); diff --git a/arch/csky/lib/usercopy.c b/arch/csky/lib/usercopy.c new file mode 100644 index 000000000..3c01c5442 --- /dev/null +++ b/arch/csky/lib/usercopy.c @@ -0,0 +1,214 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. + +#include +#include + +unsigned long raw_copy_from_user(void *to, const void *from, + unsigned long n) +{ + int tmp, nsave; + + __asm__ __volatile__( + "0: cmpnei %1, 0 \n" + " bf 7f \n" + " mov %3, %1 \n" + " or %3, %2 \n" + " andi %3, 3 \n" + " cmpnei %3, 0 \n" + " bf 1f \n" + " br 5f \n" + "1: cmplti %0, 16 \n" + " bt 3f \n" + "2: ldw %3, (%2, 0) \n" + "10: ldw %4, (%2, 4) \n" + " stw %3, (%1, 0) \n" + " stw %4, (%1, 4) \n" + "11: ldw %3, (%2, 8) \n" + "12: ldw %4, (%2, 12) \n" + " stw %3, (%1, 8) \n" + " stw %4, (%1, 12) \n" + " addi %2, 16 \n" + " addi %1, 16 \n" + " subi %0, 16 \n" + " br 1b \n" + "3: cmplti %0, 4 \n" + " bt 5f \n" + "4: ldw %3, (%2, 0) \n" + " stw %3, (%1, 0) \n" + " addi %2, 4 \n" + " addi %1, 4 \n" + " subi %0, 4 \n" + " br 3b \n" + "5: cmpnei %0, 0 \n" + " bf 7f \n" + "6: ldb %3, (%2, 0) \n" + " stb %3, (%1, 0) \n" + " addi %2, 1 \n" + " addi %1, 1 \n" + " subi %0, 1 \n" + " br 5b \n" + "8: stw %3, (%1, 0) \n" + " subi %0, 4 \n" + " bf 7f \n" + "9: subi %0, 8 \n" + " bf 7f \n" + "13: stw %3, (%1, 8) \n" + " subi %0, 12 \n" + " bf 7f \n" + ".section __ex_table, \"a\" \n" + ".align 2 \n" + ".long 2b, 7f \n" + ".long 4b, 7f \n" + ".long 6b, 7f \n" + ".long 10b, 8b \n" + ".long 11b, 9b \n" + ".long 12b,13b \n" + ".previous \n" + "7: \n" + : "=r"(n), "=r"(to), "=r"(from), "=r"(nsave), + "=r"(tmp) + : "0"(n), "1"(to), "2"(from) + : "memory"); + + return n; +} +EXPORT_SYMBOL(raw_copy_from_user); + +unsigned long raw_copy_to_user(void *to, const void *from, + unsigned long n) +{ + int w0, w1, w2, w3; + + __asm__ __volatile__( + "0: cmpnei %1, 0 \n" + " bf 8f \n" + " mov %3, %1 \n" + " or %3, %2 \n" + " andi %3, 3 \n" + " cmpnei %3, 0 \n" + " bf 1f \n" + " br 5f \n" + "1: cmplti %0, 16 \n" /* 4W */ + " bt 3f \n" + " ldw %3, (%2, 0) \n" + " ldw %4, (%2, 4) \n" + " ldw %5, (%2, 8) \n" + " ldw %6, (%2, 12) \n" + "2: stw %3, (%1, 0) \n" + "9: stw %4, (%1, 4) \n" + "10: stw %5, (%1, 8) \n" + "11: stw %6, (%1, 12) \n" + " addi %2, 16 \n" + " addi %1, 16 \n" + " subi %0, 16 \n" + " br 1b \n" + "3: cmplti %0, 4 \n" /* 1W */ + " bt 5f \n" + " ldw %3, (%2, 0) \n" + "4: stw %3, (%1, 0) \n" + " addi %2, 4 \n" + " addi %1, 4 \n" + " subi %0, 4 \n" + " br 3b \n" + "5: cmpnei %0, 0 \n" /* 1B */ + " bf 13f \n" + " ldb %3, (%2, 0) \n" + "6: stb %3, (%1, 0) \n" + " addi %2, 1 \n" + " addi %1, 1 \n" + " subi %0, 1 \n" + " br 5b \n" + "7: subi %0, 4 \n" + "8: subi %0, 4 \n" + "12: subi %0, 4 \n" + " br 13f \n" + ".section __ex_table, \"a\" \n" + ".align 2 \n" + ".long 2b, 13f \n" + ".long 4b, 13f \n" + ".long 6b, 13f \n" + ".long 9b, 12b \n" + ".long 10b, 8b \n" + ".long 11b, 7b \n" + ".previous \n" + "13: \n" + : "=r"(n), "=r"(to), "=r"(from), "=r"(w0), + "=r"(w1), "=r"(w2), "=r"(w3) + : "0"(n), "1"(to), "2"(from) + : "memory"); + + return n; +} +EXPORT_SYMBOL(raw_copy_to_user); + +/* + * __clear_user: - Zero a block of memory in user space, with less checking. + * @to: Destination address, in user space. + * @n: Number of bytes to zero. + * + * Zero a block of memory in user space. Caller must check + * the specified block with access_ok() before calling this function. + * + * Returns number of bytes that could not be cleared. + * On success, this will be zero. + */ +unsigned long +__clear_user(void __user *to, unsigned long n) +{ + int data, value, tmp; + + __asm__ __volatile__( + "0: cmpnei %1, 0 \n" + " bf 7f \n" + " mov %3, %1 \n" + " andi %3, 3 \n" + " cmpnei %3, 0 \n" + " bf 1f \n" + " br 5f \n" + "1: cmplti %0, 32 \n" /* 4W */ + " bt 3f \n" + "8: stw %2, (%1, 0) \n" + "10: stw %2, (%1, 4) \n" + "11: stw %2, (%1, 8) \n" + "12: stw %2, (%1, 12) \n" + "13: stw %2, (%1, 16) \n" + "14: stw %2, (%1, 20) \n" + "15: stw %2, (%1, 24) \n" + "16: stw %2, (%1, 28) \n" + " addi %1, 32 \n" + " subi %0, 32 \n" + " br 1b \n" + "3: cmplti %0, 4 \n" /* 1W */ + " bt 5f \n" + "4: stw %2, (%1, 0) \n" + " addi %1, 4 \n" + " subi %0, 4 \n" + " br 3b \n" + "5: cmpnei %0, 0 \n" /* 1B */ + "9: bf 7f \n" + "6: stb %2, (%1, 0) \n" + " addi %1, 1 \n" + " subi %0, 1 \n" + " br 5b \n" + ".section __ex_table,\"a\" \n" + ".align 2 \n" + ".long 8b, 9b \n" + ".long 10b, 9b \n" + ".long 11b, 9b \n" + ".long 12b, 9b \n" + ".long 13b, 9b \n" + ".long 14b, 9b \n" + ".long 15b, 9b \n" + ".long 16b, 9b \n" + ".long 4b, 9b \n" + ".long 6b, 9b \n" + ".previous \n" + "7: \n" + : "=r"(n), "=r" (data), "=r"(value), "=r"(tmp) + : "0"(n), "1"(to), "2"(0) + : "memory"); + + return n; +} +EXPORT_SYMBOL(__clear_user); -- cgit v1.3.1