Commit 4a912f99 authored by Zheng Yejian's avatar Zheng Yejian
Browse files

livepatch: Fix find wrong ftrace entry 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9UQ7I



--------------------------------

There is case that 'kernel_kexec' has multiple fentrys, and when
CONFIG_LIVEPATCH_ISOLATE_KPROBE enable, livepatch want to find the
fentry at function start, however it actually find a wrong fentry due
to binary search in ftrace_location_range() through the whole function
range.

  # grep kernel_kexec /sys/kernel/tracing/available_filter_functions
  kernel_kexec  <-- kernel_kexec+0x4/0xf8
  kernel_kexec  <-- kernel_kexec+0xdc/0xf8
  kernel_kexec  <-- kernel_kexec+0xdc/0xf8

To solve the issue, shrink the search range in first several
instructions.

Fixes: fe25ad14 ("livepatch: Avoid patching conflicts with kprobes")
Signed-off-by: default avatarZheng Yejian <zhengyejian1@huawei.com>
parent 83e8197d

arch/arm64/kernel/livepatch.c

+11 −0
Original line number Diff line number Diff line
@@ -330,3 +330,14 @@ void arch_klp_unpatch_func(struct klp_func *func) 
		do_patch(pc, (unsigned long)next_func->new_func);

	}

}



#ifdef CONFIG_LIVEPATCH_ISOLATE_KPROBE

unsigned long arch_klp_fentry_range_size(void)

{

	/*

	 * If first instruction is not 'bti', expect fentry exists

	 * at second instruction otherwise third instruction.

	 */

	return 3 * AARCH64_INSN_SIZE;

}

#endif /* CONFIG_LIVEPATCH_ISOLATE_KPROBE */

arch/x86/kernel/livepatch.c

+18 −0
Original line number Diff line number Diff line
@@ -386,4 +386,22 @@ void arch_klp_unpatch_func(struct klp_func *func) 
	/* replace the text with the new text */

	klp_patch_text((void *)ip, (const void *)new, JMP_E9_INSN_SIZE);

}



#ifdef CONFIG_LIVEPATCH_ISOLATE_KPROBE

unsigned long arch_klp_fentry_range_size(void)

{

	/*

	 * If CONFIG_X86_KERNEL_IBT enabled, there would be an 'endbr64'

	 * at function start, then it should be consider into the range

	 * size. But since CONFIG_X86_KERNEL_IBT is not introduced in this

	 * version, add a check here avoid this patch being port to later

	 * version but this case not being handled.

	 */

#ifdef CONFIG_X86_KERNEL_IBT

	BUILD_BUG_ON(1);

#endif

	/* Expect fentry exists at first instruction. */

	return MCOUNT_INSN_SIZE;

}

#endif /* CONFIG_LIVEPATCH_ISOLATE_KPROBE */

#endif

kernel/livepatch/core.c

+35 −7
Original line number Diff line number Diff line
@@ -984,6 +984,33 @@ int __weak arch_klp_init_func(struct klp_object *obj, struct klp_func *func) 
{

	return 0;

}



#ifdef CONFIG_LIVEPATCH_ISOLATE_KPROBE

unsigned long __weak arch_klp_fentry_range_size(void)

{

	return 0;

}



static unsigned long klp_ftrace_location(unsigned long func_addr,

					 unsigned long func_size)

{

	unsigned long loc;

	unsigned long range_size = arch_klp_fentry_range_size();



	/*

	 * When some arch not need to modify codes after fentry, they are no

	 * need to override the weak arch_klp_fentry_range_size() which return

	 * 0, so just return here.

	 */

	if (range_size == 0 || range_size > func_size)

		return 0;

	loc = ftrace_location_range(func_addr, func_addr + range_size);

	if (WARN_ON(loc && (loc < func_addr || loc >= func_addr + range_size)))

		loc = 0;

	return loc;

}

#endif /* CONFIG_LIVEPATCH_ISOLATE_KPROBE */



#endif



static int klp_init_func(struct klp_object *obj, struct klp_func *func)
@@ -1089,15 +1116,16 @@ static int klp_init_object_loaded(struct klp_patch *patch, 
		}

#ifdef CONFIG_LIVEPATCH_ISOLATE_KPROBE

		old_func = (unsigned long)func->old_func;

		ftrace_loc = ftrace_location_range(old_func, old_func + func->old_size - 1);

		ftrace_loc = klp_ftrace_location(old_func, func->old_size);

		if (ftrace_loc) {

			if (WARN_ON(ftrace_loc < old_func ||

			    ftrace_loc >= old_func + func->old_size - MCOUNT_INSN_SIZE)) {

				pr_err("ftrace location for '%s' invalid", func->old_name);

				return -EINVAL;

			}

			if (ftrace_loc >= old_func &&

			    ftrace_loc < old_func + func->old_size - MCOUNT_INSN_SIZE) {

				func->old_func = (void *)(ftrace_loc + MCOUNT_INSN_SIZE);

				func->old_size -= ((unsigned long)func->old_func - old_func);

			} else {

				pr_warn("space not enough after ftrace location in '%s'\n",

					func->old_name);

			}

		}

#endif