On Thu, 17 Jan 2019 09:08:41 +0100 Andreas Ziegler <andreas.zieg...@fau.de> wrote:
> On 17.01.19 09:00, Masami Hiramatsu wrote: > > On Thu, 17 Jan 2019 15:13:09 +0900 > > Masami Hiramatsu <mhira...@kernel.org> wrote: > > > >> On Wed, 16 Jan 2019 11:16:07 +0100 > >> Andreas Ziegler <andreas.zieg...@fau.de> wrote: > >> > >>> > >>> I went into this a bit deeper today, and right now it is simply failing > >>> to parse the code because there is no FETCH_OP_COMM case in > >>> process_fetch_insn() for uprobes so that will return -EILSEQ, leading to > >>> a make_data_loc(0, ...) in store_trace_args(). If we just add > >>> FETCH_OP_COMM and let val point to current->comm (that's what > >>> trace_kprobe.c does), we get an -EFAULT return value from > >>> fetch_store_string because strncpy_from_user() checks if the argument is > >>> in user space. > >> > >> Correct. I missed to add OP_COMM support. And uprobe's fetch_store_string > >> is only for user space strings. > >> > >>> So I think we might need a special case for that, something like > >>> FETCH_OP_ST_COMM_STRING which is only used for FETCH_OP_COMM and copies > >>> current->comm over to the dynamic area. The implementation could be > >>> similar to the old fetch_comm_string implementation before your rewrite. > >> > >> Hmm, instead, I would like to add current->comm checker and only allows > >> to copy that. That would be simpler and enough. > >> > >> Could you test below patch? > >> > >> > >> tracing: uprobes: Re-enable $comm support for uprobe events > >> > >> From: Masami Hiramatsu <mhira...@kernel.org> > >> > >> Since commit 533059281ee5 ("tracing: probeevent: Introduce new > >> argument fetching code") dropped the $comm support from uprobe > >> events, this re-enable it. > > this should read 're-enables'. > > >> > >> For $comm support, use strncpy() instead of strncpy_from_user() > ^ > we're using strlcpy(), not strncpy(). > > >> to copy current task's comm. Because it is in the kernel space, > >> strncpy_from_user() always fails to copy the comm. > >> This also use strlen() instead of strlen_user() to measure the > ^ ^ > 'uses', and the function should be 'strnlen_user()'. > > >> length of the comm. > >> > >> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> > >> Reported-by: Andreas Ziegler <andreas.zieg...@fau.de> > >> --- > >> kernel/trace/trace_uprobe.c | 13 +++++++++++-- > >> 1 file changed, 11 insertions(+), 2 deletions(-) > >> > >> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > >> index e335576b9411..97d134e83e0f 100644 > >> --- a/kernel/trace/trace_uprobe.c > >> +++ b/kernel/trace/trace_uprobe.c > >> @@ -156,7 +156,10 @@ fetch_store_string(unsigned long addr, void *dest, > >> void *base) > >> if (unlikely(!maxlen)) > >> return -ENOMEM; > >> > >> - ret = strncpy_from_user(dst, src, maxlen); > >> + if (addr == (unsigned long)current->comm) > >> + ret = strlcpy(dst, current->comm, maxlen); > >> + else > >> + ret = strncpy_from_user(dst, src, maxlen); > >> if (ret >= 0) { > >> if (ret == maxlen) > >> dst[ret - 1] = '\0'; > >> @@ -173,7 +176,10 @@ fetch_store_strlen(unsigned long addr) > >> int len; > >> void __user *vaddr = (void __force __user *) addr; > >> > >> - len = strnlen_user(vaddr, MAX_STRING_SIZE); > >> + if (addr == (unsigned long)current->comm) > >> + len = strlen(current->comm); > > > > To balance with the strnlen_user, we must increse the len in this block. > > (strlen doesn't count the final '\0', but strnlen_user counts it) > > > > yes, we need to add a '+ 1' here. > > With the typos and this one fixed, this is > > Acked-by: Andreas Ziegler <andreas.zieg...@fau.de> Thank you for fixing typo and Ack :) Thanks you, > > > Thank you, > > > >> + else > >> + len = strnlen_user(vaddr, MAX_STRING_SIZE); > >> > >> return (len > MAX_STRING_SIZE) ? 0 : len; > >> } > >> @@ -213,6 +219,9 @@ process_fetch_insn(struct fetch_insn *code, struct > >> pt_regs *regs, void *dest, > >> case FETCH_OP_IMM: > >> val = code->immediate; > >> break; > >> + case FETCH_OP_COMM: > >> + val = (unsigned long)current->comm; > >> + break; > >> case FETCH_OP_FOFFS: > >> val = translate_user_vaddr(code->immediate); > >> break; > > > > > -- Masami Hiramatsu <mhira...@kernel.org>