From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>
Subject: Re: [RFC bpf-next 1/4] kallsyms: Add kallsyms_lookup_names function
Date: Mon, 11 Apr 2022 15:15:23 -0700 [thread overview]
Message-ID: <CAEf4BzYffXGFigxywjP391s4G=6VpykxaqD5OYuOR5mBRa1Tmw@mail.gmail.com> (raw)
In-Reply-To: <20220407125224.310255-2-jolsa@kernel.org>
On Thu, Apr 7, 2022 at 5:52 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding kallsyms_lookup_names function that resolves array of symbols
> with single pass over kallsyms.
>
> The user provides array of string pointers with count and pointer to
> allocated array for resolved values.
>
> int kallsyms_lookup_names(const char **syms, u32 cnt,
> unsigned long *addrs)
>
> Before we iterate kallsyms we sort user provided symbols by name and
> then use that in kalsyms iteration to find each kallsyms symbol in
> user provided symbols.
>
> We also check each symbol to pass ftrace_location, because this API
> will be used for fprobe symbols resolving. This can be optional in
> future if there's a need.
>
> Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> include/linux/kallsyms.h | 6 +++++
> kernel/kallsyms.c | 48 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
> index ce1bd2fbf23e..5320a5e77f61 100644
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -72,6 +72,7 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
> #ifdef CONFIG_KALLSYMS
> /* Lookup the address for a symbol. Returns 0 if not found. */
> unsigned long kallsyms_lookup_name(const char *name);
> +int kallsyms_lookup_names(const char **syms, u32 cnt, unsigned long *addrs);
>
> extern int kallsyms_lookup_size_offset(unsigned long addr,
> unsigned long *symbolsize,
> @@ -103,6 +104,11 @@ static inline unsigned long kallsyms_lookup_name(const char *name)
> return 0;
> }
>
> +int kallsyms_lookup_names(const char **syms, u32 cnt, unsigned long *addrs)
> +{
> + return -ERANGE;
> +}
> +
> static inline int kallsyms_lookup_size_offset(unsigned long addr,
> unsigned long *symbolsize,
> unsigned long *offset)
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 79f2eb617a62..a3738ddf9e87 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -29,6 +29,8 @@
> #include <linux/compiler.h>
> #include <linux/module.h>
> #include <linux/kernel.h>
> +#include <linux/bsearch.h>
> +#include <linux/sort.h>
>
> /*
> * These will be re-linked against their real values
> @@ -572,6 +574,52 @@ int sprint_backtrace_build_id(char *buffer, unsigned long address)
> return __sprint_symbol(buffer, address, -1, 1, 1);
> }
>
> +static int symbols_cmp(const void *a, const void *b)
isn't this literally strcmp? Or compiler will actually complain about
const void * vs const char *?
> +{
> + const char **str_a = (const char **) a;
> + const char **str_b = (const char **) b;
> +
> + return strcmp(*str_a, *str_b);
> +}
> +
> +struct kallsyms_data {
> + unsigned long *addrs;
> + const char **syms;
> + u32 cnt;
> + u32 found;
> +};
> +
> +static int kallsyms_callback(void *data, const char *name,
> + struct module *mod, unsigned long addr)
> +{
> + struct kallsyms_data *args = data;
> +
> + if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp))
> + return 0;
> +
> + addr = ftrace_location(addr);
> + if (!addr)
> + return 0;
> +
> + args->addrs[args->found++] = addr;
> + return args->found == args->cnt ? 1 : 0;
> +}
> +
> +int kallsyms_lookup_names(const char **syms, u32 cnt, unsigned long *addrs)
> +{
> + struct kallsyms_data args;
> +
> + sort(syms, cnt, sizeof(*syms), symbols_cmp, NULL);
> +
> + args.addrs = addrs;
> + args.syms = syms;
> + args.cnt = cnt;
> + args.found = 0;
> + kallsyms_on_each_symbol(kallsyms_callback, &args);
> +
> + return args.found == args.cnt ? 0 : -EINVAL;
ESRCH or ENOENT makes a bit more sense as an error?
> +}
> +
> /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
> struct kallsym_iter {
> loff_t pos;
> --
> 2.35.1
>
next prev parent reply other threads:[~2022-04-11 22:15 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 12:52 [RFC bpf-next 0/4] bpf: Speed up symbol resolving in kprobe multi link Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 1/4] kallsyms: Add kallsyms_lookup_names function Jiri Olsa
2022-04-08 0:57 ` Masami Hiramatsu
2022-04-13 7:27 ` Jiri Olsa
2022-04-08 23:19 ` Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-12 20:46 ` Jiri Olsa
2022-04-15 0:47 ` Masami Hiramatsu
2022-04-15 22:39 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko [this message]
2022-04-12 20:28 ` Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 2/4] fprobe: Resolve symbols with kallsyms_lookup_names Jiri Olsa
2022-04-08 0:58 ` Masami Hiramatsu
2022-04-07 12:52 ` [RFC bpf-next 3/4] bpf: Resolve symbols with kallsyms_lookup_names for kprobe multi link Jiri Olsa
2022-04-08 23:26 ` Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-12 18:42 ` Jiri Olsa
2022-04-07 12:52 ` [RFC bpf-next 4/4] selftests/bpf: Add attach bench test Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-12 0:49 ` Masami Hiramatsu
2022-04-12 22:51 ` Andrii Nakryiko
2022-04-16 14:21 ` Masami Hiramatsu
2022-04-18 17:33 ` Steven Rostedt
2022-04-28 13:58 ` Steven Rostedt
2022-04-28 13:59 ` Steven Rostedt
2022-04-28 18:59 ` Alexei Starovoitov
2022-04-28 20:05 ` Steven Rostedt
2022-04-28 23:32 ` Andrii Nakryiko
2022-04-28 23:53 ` Steven Rostedt
2022-04-29 0:09 ` Steven Rostedt
2022-04-29 0:31 ` Steven Rostedt
2022-04-13 16:44 ` Steven Rostedt
2022-04-13 16:45 ` Andrii Nakryiko
2022-04-13 16:59 ` Steven Rostedt
2022-04-13 19:02 ` Andrii Nakryiko
2022-04-12 15:44 ` Jiri Olsa
2022-04-12 22:59 ` Andrii Nakryiko
2022-04-08 23:29 ` [RFC bpf-next 0/4] bpf: Speed up symbol resolving in kprobe multi link Alexei Starovoitov
2022-04-09 20:24 ` Jiri Olsa
2022-04-11 22:15 ` Andrii Nakryiko
2022-04-11 22:18 ` Alexei Starovoitov
2022-04-11 22:21 ` Andrii Nakryiko
2022-04-12 15:46 ` Jiri Olsa
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