Re: [RFC PATCH 5/9] powerpc/kprobes: Use ftrace to determine if a probe is at function entry
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2023-12-11 05:40:01
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On Fri, 8 Dec 2023 22:00:44 +0530 Naveen N Rao [off-list ref] wrote:
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.
OK, so this can cover both KPROBES_ON_FTRACE=y/n cases and the function is traced by ftrace or not. Looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thanks,
quoted hunk ↗ jump to hunk
Signed-off-by: Naveen N Rao <naveen@kernel.org> --- arch/powerpc/kernel/kprobes.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index b20ee72e873a..42665dfab59e 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c@@ -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 - return offset <= 8; -#endif -#else + unsigned long ip = ftrace_location(addr); + + if (ip) + return offset <= (ip - addr); + if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2)) + return offset <= 8; 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); }-- 2.43.0
-- Masami Hiramatsu (Google) [off-list ref]