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Subject[PATCH v2 15/39] x86/ibt,kprobes: Fix more +0 assumptions
With IBT on, sym+0 is no longer the __fentry__ site.

NOTE: the architecture has a special case and *does* allow placing an
INT3 breakpoint over ENDBR in which case #BP has precedence over #CP
and as such we don't need to disallow probing these instructions.

NOTE: irrespective of the above; there is a complication in that
direct branches to functions are rewritten to not execute ENDBR, so
any breakpoint thereon might miss lots of actual function executions.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/kprobes/core.c | 11 +++++++++++
kernel/kprobes.c | 15 ++++++++++++---
2 files changed, 23 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1156,3 +1162,8 @@ int arch_trampoline_kprobe(struct kprobe
{
return 0;
}
+
+bool arch_kprobe_on_func_entry(unsigned long offset)
+{
+ return offset <= 4*HAS_KERNEL_IBT;
+}
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -67,10 +67,19 @@ static bool kprobes_all_disarmed;
static DEFINE_MUTEX(kprobe_mutex);
static DEFINE_PER_CPU(struct kprobe *, kprobe_instance);

-kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
- unsigned int __unused)
+kprobe_opcode_t * __weak kprobe_lookup_name(const char *name, unsigned int offset)
{
- return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
+ kprobe_opcode_t *addr = NULL;
+
+ addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ if (addr && !offset) {
+ unsigned long faddr = ftrace_location((unsigned long)addr);
+ if (faddr)
+ addr = (kprobe_opcode_t *)faddr;
+ }
+#endif
+ return addr;
}

/*

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