Commit be87d713 authored by Naveen N Rao's avatar Naveen N Rao Committed by Michael Ellerman
Browse files

powerpc/kprobes: Use ftrace to determine if a probe is at function entry 



Rather than hard-coding the offset into a function to be used to
determine if a kprobe is at function entry, use ftrace_location() to
determine the ftrace location within the function and categorize all
instructions till that offset to be function entry.

For functions that cannot be traced, we fall back to using a fixed
offset of 8 (two instructions) to categorize a probe as being at
function entry for 64-bit elfv2, unless we are using pcrel.

Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarNaveen N Rao <naveen@kernel.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-3-hbathini@linux.ibm.com
parent 0b984652

arch/powerpc/kernel/kprobes.c

+8 −10
Original line number Diff line number Diff line
@@ -105,24 +105,22 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset) 
	return addr;

}



static bool arch_kprobe_on_func_entry(unsigned long offset)

static bool arch_kprobe_on_func_entry(unsigned long addr, unsigned long offset)

{

#ifdef CONFIG_PPC64_ELF_ABI_V2

#ifdef CONFIG_KPROBES_ON_FTRACE

	return offset <= 16;

#else

	unsigned long ip = ftrace_location(addr);



	if (ip)

		return offset <= (ip - addr);

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))

		return offset <= 8;

#endif

#else

	return !offset;

#endif

}



/* XXX try and fold the magic of kprobe_lookup_name() in this */

kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,

					 bool *on_func_entry)

{

	*on_func_entry = arch_kprobe_on_func_entry(offset);

	*on_func_entry = arch_kprobe_on_func_entry(addr, offset);

	return (kprobe_opcode_t *)(addr + offset);

}