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[94.113.247.30]) by smtp.gmail.com with ESMTPSA id y15-20020a05600015cf00b00203e324347bsm26840249wry.102.2022.04.09.13.24.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 09 Apr 2022 13:24:34 -0700 (PDT) Date: Sat, 9 Apr 2022 22:24:32 +0200 From: Jiri Olsa To: Alexei Starovoitov Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Masami Hiramatsu , netdev@vger.kernel.org, bpf@vger.kernel.org, lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh Subject: Re: [RFC bpf-next 1/4] kallsyms: Add kallsyms_lookup_names function Message-ID: References: <20220407125224.310255-1-jolsa@kernel.org> <20220407125224.310255-2-jolsa@kernel.org> <20220408231925.uc2cfeev7p6nzfww@MBP-98dd607d3435.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220408231925.uc2cfeev7p6nzfww@MBP-98dd607d3435.dhcp.thefacebook.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Apr 08, 2022 at 04:19:25PM -0700, Alexei Starovoitov wrote: > On Thu, Apr 07, 2022 at 02:52:21PM +0200, Jiri Olsa 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 > > Signed-off-by: Jiri Olsa > > --- > > 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 > > #include > > #include > > +#include > > +#include > > > > /* > > * 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) > > +{ > > + 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); > > It's nice to share symbols_cmp for sort and bsearch, > but messing technically input argument 'syms' like this will cause > issues sooner or later. > Lets make caller do the sort. > Unordered input will cause issue with bsearch, of course, > but it's a lesser evil. imo. ok, will move it out and make some proper comment for the function mentioning the sort requirement for syms thanks, jirka > > > + > > + 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; > > +} > > + > > /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */ > > struct kallsym_iter { > > loff_t pos; > > -- > > 2.35.1 > >