From: Rong Tao rongtao@cestc.cn
Static ksyms often have problems because the number of symbols exceeds the MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves the problem somewhat, but it's not the perfect way.
This commit uses dynamic memory allocation, which completely solves the problem caused by the limitation of the number of kallsyms.
Acked-by: Stanislav Fomichev sdf@google.com Signed-off-by: Rong Tao rongtao@cestc.cn --- v5: Release the allocated memory once the load_kallsyms_refresh() upon error given it's dynamically allocated. v4: https://lore.kernel.org/lkml/tencent_59C74613113F0C728524B2A82FE5540A5E09@qq... Make sure most cases we don't need the realloc() path to begin with, and check strdup() return value. v3: https://lore.kernel.org/lkml/tencent_50B4B2622FE7546A5FF9464310650C008509@qq... Do not use structs and judge ksyms__add_symbol function return value. v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq... Do the usual len/capacity scheme here to amortize the cost of realloc, and don't free symbols. v1: https://lore.kernel.org/lkml/tencent_AB461510B10CD484E0B2F62E3754165F2909@qq... --- tools/testing/selftests/bpf/trace_helpers.c | 62 +++++++++++++++++---- 1 file changed, 52 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index f83d9f65c65b..0053ba22f0cb 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -18,10 +18,47 @@ #define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe" #define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
-#define MAX_SYMS 400000 -static struct ksym syms[MAX_SYMS]; +static struct ksym *syms; +static int sym_cap; static int sym_cnt;
+static int ksyms__add_symbol(const char *name, unsigned long addr) +{ + void *tmp; + unsigned int new_cap; + + if (sym_cnt + 1 > sym_cap) { + new_cap = sym_cap * 4 / 3; + tmp = realloc(syms, sizeof(struct ksym) * new_cap); + if (!tmp) + return -ENOMEM; + syms = tmp; + sym_cap = new_cap; + } + + tmp = strdup(name); + if (!tmp) + return -ENOMEM; + syms[sym_cnt].addr = addr; + syms[sym_cnt].name = tmp; + + sym_cnt++; + + return 0; +} + +static void ksyms__free(void) +{ + unsigned int i; + + if (!syms) + return; + + for (i = 0; i < sym_cnt; i++) + free(syms[i].name); + free(syms); +} + static int ksym_cmp(const void *p1, const void *p2) { return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr; @@ -33,9 +70,14 @@ int load_kallsyms_refresh(void) char func[256], buf[256]; char symbol; void *addr; - int i = 0; + int ret;
+ /* Make sure most cases we don't need the realloc() path to begin with */ + sym_cap = 400000; sym_cnt = 0; + syms = malloc(sizeof(struct ksym) * sym_cap); + if (!syms) + return -ENOMEM;
f = fopen("/proc/kallsyms", "r"); if (!f) @@ -46,17 +88,17 @@ int load_kallsyms_refresh(void) break; if (!addr) continue; - if (i >= MAX_SYMS) - return -EFBIG; - - syms[i].addr = (long) addr; - syms[i].name = strdup(func); - i++; + ret = ksyms__add_symbol(func, (unsigned long)addr); + if (ret) + goto error; } fclose(f); - sym_cnt = i; qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp); return 0; + +error: + ksyms__free(); + return ret; }
int load_kallsyms(void)
On Thu, Aug 17, 2023 at 01:03:45PM +0800, Rong Tao wrote:
From: Rong Tao rongtao@cestc.cn
Static ksyms often have problems because the number of symbols exceeds the MAX_SYMS limit. Like changing the MAX_SYMS from 300000 to 400000 in commit e76a014334a6("selftests/bpf: Bump and validate MAX_SYMS") solves the problem somewhat, but it's not the perfect way.
This commit uses dynamic memory allocation, which completely solves the problem caused by the limitation of the number of kallsyms.
Acked-by: Stanislav Fomichev sdf@google.com Signed-off-by: Rong Tao rongtao@cestc.cn
v5: Release the allocated memory once the load_kallsyms_refresh() upon error given it's dynamically allocated. v4: https://lore.kernel.org/lkml/tencent_59C74613113F0C728524B2A82FE5540A5E09@qq... Make sure most cases we don't need the realloc() path to begin with, and check strdup() return value. v3: https://lore.kernel.org/lkml/tencent_50B4B2622FE7546A5FF9464310650C008509@qq... Do not use structs and judge ksyms__add_symbol function return value. v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq... Do the usual len/capacity scheme here to amortize the cost of realloc, and don't free symbols. v1: https://lore.kernel.org/lkml/tencent_AB461510B10CD484E0B2F62E3754165F2909@qq...
tools/testing/selftests/bpf/trace_helpers.c | 62 +++++++++++++++++---- 1 file changed, 52 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index f83d9f65c65b..0053ba22f0cb 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -18,10 +18,47 @@ #define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe" #define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe" -#define MAX_SYMS 400000 -static struct ksym syms[MAX_SYMS]; +static struct ksym *syms; +static int sym_cap; static int sym_cnt; +static int ksyms__add_symbol(const char *name, unsigned long addr) +{
- void *tmp;
- unsigned int new_cap;
- if (sym_cnt + 1 > sym_cap) {
new_cap = sym_cap * 4 / 3;tmp = realloc(syms, sizeof(struct ksym) * new_cap);if (!tmp)return -ENOMEM;syms = tmp;sym_cap = new_cap;- }
sorry I did not notice earlier, but we have helper for realloc
libbpf_ensure_mem
check the usage for example in prog_tests/kprobe_multi_test.c
- tmp = strdup(name);
- if (!tmp)
return -ENOMEM;- syms[sym_cnt].addr = addr;
- syms[sym_cnt].name = tmp;
- sym_cnt++;
- return 0;
+}
+static void ksyms__free(void) +{
- unsigned int i;
- if (!syms)
return;- for (i = 0; i < sym_cnt; i++)
free(syms[i].name);- free(syms);
+}
static int ksym_cmp(const void *p1, const void *p2) { return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr; @@ -33,9 +70,14 @@ int load_kallsyms_refresh(void) char func[256], buf[256]; char symbol; void *addr;
- int i = 0;
- int ret;
- /* Make sure most cases we don't need the realloc() path to begin with */
- sym_cap = 400000; sym_cnt = 0;
- syms = malloc(sizeof(struct ksym) * sym_cap);
- if (!syms)
return -ENOMEM;
libbpf_ensure_mem will also take care of first allocation and the capacity increase
jirka
f = fopen("/proc/kallsyms", "r"); if (!f) @@ -46,17 +88,17 @@ int load_kallsyms_refresh(void) break; if (!addr) continue;
if (i >= MAX_SYMS)return -EFBIG;syms[i].addr = (long) addr;syms[i].name = strdup(func);i++;
ret = ksyms__add_symbol(func, (unsigned long)addr);if (ret)goto error;
- sym_cnt = i; qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp); return 0;
+error:
- ksyms__free();
- return ret;
} int load_kallsyms(void) -- 2.39.3
Hi, Jiri. Thanks for your reply.
libbpf_ensure_mem() is in libbpf_internal.h, samples/bpf/ can't see it, do we reposition the function declaration?
Good Day Rong Tao
On Fri, Aug 18, 2023 at 09:39:32AM +0800, Rong Tao wrote:
Hi, Jiri. Thanks for your reply.
libbpf_ensure_mem() is in libbpf_internal.h, samples/bpf/ can't see it, do we reposition the function declaration?
I see, I had no idea trace_helpers.[ch] is included in samples/bpf
but it seems to have libbpf linked statically.. so you could just include libbpf_internal.h and it should work, right? like we do in selftests
jirka
Good Day Rong Tao
Hi, jirka
Sadly, we can't include libbpf_internal.h in trace_helpers.{h,c}. we only have the following headers when compile samples/bpf/:
tree of samples/bpf/libbpf/ +-- bpf_helper_defs.h +-- include |���� '-- bpf |���� +-- bpf_core_read.h |���� +-- bpf_endian.h |���� +-- bpf.h |���� +-- bpf_helper_defs.h |���� +-- bpf_helpers.h |���� +-- bpf_tracing.h |���� +-- btf.h |���� +-- libbpf_common.h |���� +-- libbpf.h |���� +-- libbpf_legacy.h |���� +-- libbpf_version.h |���� +-- skel_internal.h |���� '-- usdt.bpf.h +-- libbpf.a
No libbpf_internal.h here.
What if we add a declaration to libbpf_ensure_mem() in trace_helpers.c?
Good Day, Rong Tao
On 8/18/23 8:36 AM, Rong Tao wrote:
Hi, jirka
Sadly, we can't include libbpf_internal.h in trace_helpers.{h,c}. we only have the following headers when compile samples/bpf/:
tree of samples/bpf/libbpf/ +-- bpf_helper_defs.h +-- include | '-- bpf | +-- bpf_core_read.h | +-- bpf_endian.h | +-- bpf.h | +-- bpf_helper_defs.h | +-- bpf_helpers.h | +-- bpf_tracing.h | +-- btf.h | +-- libbpf_common.h | +-- libbpf.h | +-- libbpf_legacy.h | +-- libbpf_version.h | +-- skel_internal.h | '-- usdt.bpf.h +-- libbpf.a
No libbpf_internal.h here.
What if we add a declaration to libbpf_ensure_mem() in trace_helpers.c?
[~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$ grep libbpf_internal.h * cpu_mask.c:#include "bpf/libbpf_internal.h" kprobe_multi_test.c:#include "bpf/libbpf_internal.h" kprobe_multi_testmod_test.c:#include "bpf/libbpf_internal.h" module_fentry_shadow.c:#include "bpf/libbpf_internal.h" perf_branches.c:#include "bpf/libbpf_internal.h" perf_buffer.c:#include "bpf/libbpf_internal.h" raw_tp_test_run.c:#include "bpf/libbpf_internal.h" [~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$ grep libbpf_ensure_mem *.c kprobe_multi_test.c: err = libbpf_ensure_mem((void **) &syms, &cap, [~/work/bpf-next/tools/testing/selftests/bpf/prog_tests (master)]$
Looks like it is already used for selftets.
The libbpf_internal.h exists in the following directory when you build the selftest.
[~/work/bpf-next/tools/testing/selftests/bpf/tools/include/bpf (master)]$ ls bpf_core_read.h bpf.h bpf_helpers.h btf.h libbpf_common.h libbpf_internal.h libbpf_version.h relo_core.h usdt.bpf.h bpf_endian.h bpf_helper_defs.h bpf_tracing.h hashmap.h libbpf.h libbpf_legacy.h nlattr.h skel_internal.h
Good Day, Rong Tao
Sorry Song, I did not state clear.
libbpf_ensure_mem() is declared in libbpf_internal.h, we want to use libbpf_ensure_mem() in trace_helpers.c, Unforturnately, we could only include the headers 'install_headers:' defined in tools/lib/bpf/Makefile, the 'install_headers:' target does not include libbpf_internal.h, like:
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: libbpf_internal.h: No such file or directory 17 | #include "libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: bpf/libbpf_internal.h: No such file or directory 17 | #include "bpf/libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~~~~~
How about
1. dup-declare libbpf_ensure_mem() in trace_helpers.c 2. move libbpf_ensure_mem() declare into libbpf_common.h
Which one do you like best.
Best wishes, Rong Tao
On 8/20/23 7:03 PM, Rong Tao wrote:
Sorry Song, I did not state clear.
libbpf_ensure_mem() is declared in libbpf_internal.h, we want to use libbpf_ensure_mem() in trace_helpers.c, Unforturnately, we could only include the headers 'install_headers:' defined in tools/lib/bpf/Makefile, the 'install_headers:' target does not include libbpf_internal.h, like:
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: libbpf_internal.h: No such file or directory 17 | #include "libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: bpf/libbpf_internal.h: No such file or directory 17 | #include "bpf/libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~~~~~
It works fine for me. On top of your patch, the following works fine:
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index 0053ba22f0cb..087383c5dc3a 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -14,6 +14,7 @@ #include <linux/limits.h> #include <libelf.h> #include <gelf.h> +#include "bpf/libbpf_internal.h"
#define TRACEFS_PIPE "/sys/kernel/tracing/trace_pipe" #define DEBUGFS_PIPE "/sys/kernel/debug/tracing/trace_pipe"
With V=1 when building selftests, the following is the compilation command line: clang --target=x86_64-linux-gnu -fintegrated-as -g -O0 -rdynamic -Wall -Werror -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include -I/home/yhs/work/bpf-next/include/generated -I/home/yhs/work/bpf-next/tools/lib -I/home/yhs/work/bpf-next/tools/include -I/home/yhs/work/bpf-next/tools/include/uapi -I/home/yhs/work/bpf-next/tools/testing/selftests/bpf -Wno-unused-command-line-argument -c trace_helpers.c -lelf -lz -lrt -lpthread -o /home/yhs/work/bpf-next/tools/testing/selftests/bpf/trace_helpers.o
This include path /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include will make including 'bpf/libbpf_internal.h' work.
How about
- dup-declare libbpf_ensure_mem() in trace_helpers.c
- move libbpf_ensure_mem() declare into libbpf_common.h
Which one do you like best.
Best wishes, Rong Tao
tools/testing/selftests/bpf/ compile OK, however, samples/bpf/ compile failed.
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: libbpf_internal.h: No such file or directory 17 | #include "libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~
tools/testing/selftests/bpf/trace_helpers.c:17:10: fatal error: bpf/libbpf_internal.h: No such file or directory 17 | #include "bpf/libbpf_internal.h" | ^~~~~~~~~~~~~~~~~~~~~~~
I just submit v6 [0], which apply libbpf_ensure_mem() and
TPROGS_CFLAGS += -I$(srctree)/tools/lib
to samples/bpf/Makefile, make sure, samples/bpf/Makefile could found libbpf_internal.h.
Please review, thanks.
Rong Tao
[0] https://lore.kernel.org/lkml/tencent_4A09A36F883A06EA428A593497642AF8AF08@qq...
linux-kselftest-mirror@lists.linaro.org
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Yonghong Song