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SubjectRe: [PATCH] kprobes: x86_64: blacklist non-attachable interrupt functions
Hi Andrea and Ingo,

Here is the patch what I meant. I just ran it on qemu-x86, and seemed working.
After introducing this patch, I will start adding arch_populate_kprobe_blacklist()
to some arches.

Thank you,

[RFC] kprobes: x86/kprobes: Blacklist symbols in arch-defined prohibited area

From: Masami Hiramatsu <mhiramat@kernel.org>

Blacklist symbols in arch-defined probe-prohibited areas.
With this change, user can see all symbols which are prohibited
to probe in debugfs.

All archtectures which have custom prohibit areas should define
its own arch_populate_kprobe_blacklist() function, but unless that,
all symbols marked __kprobes are blacklisted.

Reported-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 27 ++++++++++++++++++
include/linux/kprobes.h | 2 +
kernel/kprobes.c | 60 +++++++++++++++++++++++++++++++---------
3 files changed, 75 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index c33b06f..52771e3 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1034,6 +1034,33 @@ bool arch_within_kprobe_blacklist(unsigned long addr)
addr < (unsigned long)__entry_text_end);
}

+int __init arch_populate_kprobe_blacklist(void)
+{
+ unsigned long entry;
+ int ret = 0;
+
+ for (entry = (unsigned long)__kprobes_text_start;
+ entry < (unsigned long)__kprobes_text_end;
+ entry += ret) {
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) /* In case of alias symbol */
+ ret = 1;
+ }
+
+ for (entry = (unsigned long)__entry_text_start;
+ entry < (unsigned long)__entry_text_end;
+ entry += ret) {
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) /* In case of alias symbol */
+ ret = 1;
+ }
+ return 0;
+}
+
int __init arch_init_kprobes(void)
{
return 0;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e909413..a68cbbe 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -242,10 +242,12 @@ extern int arch_init_kprobes(void);
extern void show_registers(struct pt_regs *regs);
extern void kprobes_inc_nmissed_count(struct kprobe *p);
extern bool arch_within_kprobe_blacklist(unsigned long addr);
+extern int arch_populate_kprobe_blacklist(void);
extern bool arch_kprobe_on_func_entry(unsigned long offset);
extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);

extern bool within_kprobe_blacklist(unsigned long addr);
+extern int kprobe_add_ksym_blacklist(unsigned long entry);

struct kprobe_insn_cache {
struct mutex mutex;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 90e98e2..8b2eb62 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2093,6 +2093,44 @@ void dump_kprobe(struct kprobe *kp)
}
NOKPROBE_SYMBOL(dump_kprobe);

+int kprobe_add_ksym_blacklist(unsigned long entry)
+{
+ struct kprobe_blacklist_entry *ent;
+ unsigned long offset = 0, size = 0;
+
+ if (!kernel_text_address(entry) ||
+ !kallsyms_lookup_size_offset(entry, &size, &offset))
+ return -EINVAL;
+
+ ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+ if (!ent)
+ return -ENOMEM;
+ ent->start_addr = entry - offset;
+ ent->end_addr = entry - offset + size;
+ INIT_LIST_HEAD(&ent->list);
+ list_add_tail(&ent->list, &kprobe_blacklist);
+
+ return (int)size;
+}
+
+/* Add functions in arch defined probe-prohibited area */
+int __weak arch_populate_kprobe_blacklist(void)
+{
+ unsigned long entry;
+ int ret = 0;
+
+ for (entry = (unsigned long)__kprobes_text_start;
+ entry < (unsigned long)__kprobes_text_end;
+ entry += ret) {
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) /* In case of alias symbol */
+ ret = 1;
+ }
+ return 0;
+}
+
/*
* Lookup and populate the kprobe_blacklist.
*
@@ -2104,26 +2142,20 @@ NOKPROBE_SYMBOL(dump_kprobe);
static int __init populate_kprobe_blacklist(unsigned long *start,
unsigned long *end)
{
+ unsigned long entry;
unsigned long *iter;
- struct kprobe_blacklist_entry *ent;
- unsigned long entry, offset = 0, size = 0;
+ int ret;

for (iter = start; iter < end; iter++) {
entry = arch_deref_entry_point((void *)*iter);
-
- if (!kernel_text_address(entry) ||
- !kallsyms_lookup_size_offset(entry, &size, &offset))
+ ret = kprobe_add_ksym_blacklist(entry);
+ if (ret == -EINVAL)
continue;
-
- ent = kmalloc(sizeof(*ent), GFP_KERNEL);
- if (!ent)
- return -ENOMEM;
- ent->start_addr = entry;
- ent->end_addr = entry + size;
- INIT_LIST_HEAD(&ent->list);
- list_add_tail(&ent->list, &kprobe_blacklist);
+ if (ret < 0)
+ return ret;
}
- return 0;
+
+ return arch_populate_kprobe_blacklist();
}

/* Module notifier call back, checking kprobes on the module */
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