On Thu, 9 May 2019 11:15:07 +0200 Ingo Molnar <[email protected]> wrote:
> > * Masami Hiramatsu <[email protected]> wrote: > > > Add "ustring" type for fetching user-space string from kprobe event. > > User can specify ustring type at uprobe event, and it is same as > > "string" for uprobe. > > > > Note that probe-event provides this option but it doesn't choose the > > correct type automatically since we have not way to decide the address > > is in user-space or not on some arch (and on some other arch, you can > > fetch the string by "string" type). So user must carefully check the > > target code (e.g. if you see __user on the target variable) and > > use this new type. > > > > Signed-off-by: Masami Hiramatsu <[email protected]> > > Acked-by: Steven Rostedt (VMware) <[email protected]> > > > > --- > > Changes in v5: > > - Use strnlen_unsafe_user() in fetch_store_strlen_user(). > > Changes in v2: > > - Use strnlen_user() instead of open code for fetch_store_strlen_user(). > > --- > > Documentation/trace/kprobetrace.rst | 9 +++++++-- > > kernel/trace/trace.c | 2 +- > > kernel/trace/trace_kprobe.c | 29 +++++++++++++++++++++++++++++ > > kernel/trace/trace_probe.c | 14 +++++++++++--- > > kernel/trace/trace_probe.h | 1 + > > kernel/trace/trace_probe_tmpl.h | 14 +++++++++++++- > > kernel/trace/trace_uprobe.c | 12 ++++++++++++ > > 7 files changed, 74 insertions(+), 7 deletions(-) > > > > diff --git a/Documentation/trace/kprobetrace.rst > > b/Documentation/trace/kprobetrace.rst > > index 235ce2ab131a..a3ac7c9ac242 100644 > > --- a/Documentation/trace/kprobetrace.rst > > +++ b/Documentation/trace/kprobetrace.rst > > @@ -55,7 +55,8 @@ Synopsis of kprobe_events > > NAME=FETCHARG : Set NAME as the argument name of FETCHARG. > > FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types > > (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types > > - (x8/x16/x32/x64), "string" and bitfield are supported. > > + (x8/x16/x32/x64), "string", "ustring" and bitfield > > + are supported. > > > > (\*1) only for the probe on function entry (offs == 0). > > (\*2) only for return probe. > > @@ -77,7 +78,11 @@ apply it to registers/stack-entries etc. (for example, > > '$stack1:x8[8]' is > > wrong, but '+8($stack):x8[8]' is OK.) > > String type is a special type, which fetches a "null-terminated" string > > from > > kernel space. This means it will fail and store NULL if the string > > container > > -has been paged out. > > +has been paged out. "ustring" type is an alternative of string for > > user-space. > > +Note that kprobe-event provides string/ustring types, but doesn't change it > > +automatically. So user has to decide if the targe string in kernel or in > > user > > +space carefully. On some arch, if you choose wrong one, it always fails to > > +record string data. > > The string array type is a bit different from other types. For other base > > types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same > > as +0(%di):x32.) But string[1] is not equal to string. The string type > > itself > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index dcb9adb44be9..101a5d09a632 100644 > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -4858,7 +4858,7 @@ static const char readme_msg[] = > > "\t $stack<index>, $stack, $retval, $comm\n" > > #endif > > "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n" > > - "\t b<bit-width>@<bit-offset>/<container-size>,\n" > > + "\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n" > > "\t <type>\\[<array-size>\\]\n" > > #ifdef CONFIG_HIST_TRIGGERS > > "\t field: <stype> <name>;\n" > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index 7d736248a070..fcb8806fc93c 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -886,6 +886,14 @@ fetch_store_strlen(unsigned long addr) > > return (ret < 0) ? ret : len; > > } > > > > +/* Return the length of string -- including null terminal byte */ > > +static nokprobe_inline int > > +fetch_store_strlen_user(unsigned long addr) > > +{ > > + return strnlen_unsafe_user((__force const void __user *)addr, > > + MAX_STRING_SIZE); > > +} > > + > > /* > > * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max > > * length and relative data location. > > @@ -910,6 +918,27 @@ fetch_store_string(unsigned long addr, void *dest, > > void *base) > > return ret; > > } > > > > +/* > > + * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf > > + * with max length and relative data location. > > + */ > > +static nokprobe_inline int > > +fetch_store_string_user(unsigned long addr, void *dest, void *base) > > +{ > > + int maxlen = get_loc_len(*(u32 *)dest); > > + u8 *dst = get_loc_data(dest, base); > > + long ret; > > + > > + if (unlikely(!maxlen)) > > + return -ENOMEM; > > + ret = strncpy_from_unsafe_user(dst, (__force const void __user *)addr, > > + maxlen); > > Pointless line break. OK. > > > + > > + if (ret >= 0) > > + *(u32 *)dest = make_data_loc(ret, (void *)dst - base); > > + return ret; > > +} > > Plus the problem as in the earlier patch. OK, I'll fix it too. Thank you! > > Thanks, > > Ingo -- Masami Hiramatsu <[email protected]>
