Hi Peter and Josh, So here is 3rd version of the patches to fix kprobes and optprobe with CONFIG_RETHUNK and CONFIG_SLS. Previous version is here; https://lore.kernel.org/all/166260087224.759381.4170102827490658262.stgit@devnote2/ In this version, I simplified all code and just checks the INT3 comes from kgdb or not. Other INT3 are treated as one-byte instruction. With CONFIG_RETHUNK/CONFIG_SLS, the kernel functions may includes INT3 for stopping speculative execution in the function code block (body) in addition to the gaps between functions. Since kprobes on x86 has to ensure the probe address is an instruction bondary, it decodes the instructions in the function until the address. If it finds an INT3 which is not embedded by kprobe, it stops decoding because usually the INT3 is used for debugging as a software breakpoint and such INT3 will replace the first byte of an original instruction. Without recovering it, kprobes can not continue to decode it. Thus the kprobes returns -EILSEQ as below. # echo "p:probe/vfs_truncate_L19 vfs_truncate+98" >> kprobe_events sh: write error: Invalid or incomplete multibyte or wide character Actually, such INT3 can be ignored except the INT3 installed by kgdb. To avoid this issue, just check whether the INT3 is owned by kgdb or not and if so, it just stopped and return failure. With thses fixes, kprobe and optprobe can probe the kernel again with CONFIG_RETHUNK=y. # echo "p:probe/vfs_truncate_L19 vfs_truncate+98" >> kprobe_events # echo 1 > events/probe/vfs_truncate_L19/enable # cat /sys/kernel/debug/kprobes/list ffffffff81307b52 k vfs_truncate+0x62 [OPTIMIZED] Thank you, --- Masami Hiramatsu (Google) (2): x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK x86/kprobes: Fix optprobe optimization check with CONFIG_RETHUNK arch/x86/kernel/kprobes/core.c | 10 +++++++--- arch/x86/kernel/kprobes/opt.c | 28 ++++++++-------------------- 2 files changed, 15 insertions(+), 23 deletions(-) -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
