| Message ID | tencent_BD6E19C00BF565CD5C36A9A0BD828CFA210A@qq.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next,v7] selftests/bpf: trace_helpers.c: optimize kallsyms cache | expand |
On Fri, Aug 25, 2023 at 06:36:24PM +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> > --- > v7: Fix __must_check macro. > v6: https://lore.kernel.org/lkml/tencent_4A09A36F883A06EA428A593497642AF8AF08@qq.com/ > Apply libbpf_ensure_mem() > v5: https://lore.kernel.org/lkml/tencent_0E9E1A1C0981678D5E7EA9E4BDBA8EE2200A@qq.com/ > 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.com/ > 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.com/ > Do not use structs and judge ksyms__add_symbol function return value. > v2: https://lore.kernel.org/lkml/tencent_B655EE5E5D463110D70CD2846AB3262EED09@qq.com/ > 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.com/ > --- > samples/bpf/Makefile | 2 + > tools/testing/selftests/bpf/trace_helpers.c | 58 ++++++++++++++++----- > 2 files changed, 48 insertions(+), 12 deletions(-) > > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > index 4ccf4236031c..0cd45c42af2f 100644 > --- a/samples/bpf/Makefile > +++ b/samples/bpf/Makefile > @@ -175,6 +175,7 @@ TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/ > TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE) > TPROGS_CFLAGS += -I$(srctree)/tools/include > TPROGS_CFLAGS += -I$(srctree)/tools/perf > +TPROGS_CFLAGS += -I$(srctree)/tools/lib > TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0 > > ifdef SYSROOT > @@ -314,6 +315,7 @@ XDP_SAMPLE_CFLAGS += -Wall -O2 \ > > $(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS) > $(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h > +$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check= please add some comment why we did that, perhaps like: +# Override includes for trace_helpers.o because __must_check won't be +# defined in our include path. +$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check= > > -include $(BPF_SAMPLES_PATH)/Makefile.target > > diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c > index f83d9f65c65b..d62ab3b77153 100644 > --- a/tools/testing/selftests/bpf/trace_helpers.c > +++ b/tools/testing/selftests/bpf/trace_helpers.c > @@ -14,13 +14,44 @@ > #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" > > -#define MAX_SYMS 400000 > -static struct ksym syms[MAX_SYMS]; > -static int sym_cnt; > +static struct ksym *syms; > +static size_t sym_cap; > +static size_t sym_cnt; > + > +static int ksyms__add_symbol(const char *name, unsigned long addr) > +{ > + void *tmp; > + > + 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); > + syms = NULL; > + sym_cnt = 0; > + sym_cap = 0; > +} > > static int ksym_cmp(const void *p1, const void *p2) > { > @@ -33,9 +64,7 @@ int load_kallsyms_refresh(void) > char func[256], buf[256]; > char symbol; > void *addr; > - int i = 0; > - > - sym_cnt = 0; you need to release all symbols in here, for static version it was enough to zero the sym_cnt value, but we need to release current symbols now also after discussing with Daniel we found there's a problem with paralel run where both load_kallsyms and load_kallsyms_refresh and other helpers like ksym_search are racy because another test can just drop the cache that was problem even before, but I wonder now it will expose more because we will touch freed pointer instead of accessing same static array perhaps we could fix that with 2 sets of functions: - load_kallsyms ksym_search ksym_get_addr that work like now on global syms pointer, perhaps we should initialize it before we run tests or use mutex for init - struct ksym *load_kallsyms_local() ksym_search_local(struct ksym *syms, ...) ksym_get_addr_local(struct ksym *syms, ...) that work on local ksyms cache and the test frees it at the end, it would be used in all tests that need updated kallsyms data and use load_kallsyms_refresh for that jirka > + int ret; > > f = fopen("/proc/kallsyms", "r"); > if (!f) > @@ -46,17 +75,22 @@ 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 = libbpf_ensure_mem((void **) &syms, &sym_cap, > + sizeof(struct ksym), sym_cnt + 1); > + if (ret) > + goto error; > + 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) > -- > 2.39.3 >
> perhaps we could fix that with 2 sets of functions: > > - load_kallsyms > ksym_search > ksym_get_addr > > that work like now on global syms pointer, perhaps we should > initialize it before we run tests or use mutex for init > > - struct ksym *load_kallsyms_local() > ksym_search_local(struct ksym *syms, ...) > ksym_get_addr_local(struct ksym *syms, ...) > > that work on local ksyms cache and the test frees it at the end, > it would be used in all tests that need updated kallsyms data and > use load_kallsyms_refresh for that Hi, jirka How about keeping only one type of interface to avoid confusion about use and mutex locks. Like: struct ksyms *load_kallsyms(void); struct ksyms *load_kallsyms_refresh(struct ksyms *ksyms); void free_kallsyms(struct ksyms *ksyms); struct ksym *ksym_search(struct ksyms *ksyms, long key); long ksym_get_addr(struct ksyms *ksyms, const char *name); I just submit v8 [0], please review. [0] https://lore.kernel.org/lkml/tencent_6D23FE187408D965E95DFAA858BC7E8C760A@qq.com/
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index 4ccf4236031c..0cd45c42af2f 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -175,6 +175,7 @@ TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/ TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE) TPROGS_CFLAGS += -I$(srctree)/tools/include TPROGS_CFLAGS += -I$(srctree)/tools/perf +TPROGS_CFLAGS += -I$(srctree)/tools/lib TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0 ifdef SYSROOT @@ -314,6 +315,7 @@ XDP_SAMPLE_CFLAGS += -Wall -O2 \ $(obj)/$(XDP_SAMPLE): TPROGS_CFLAGS = $(XDP_SAMPLE_CFLAGS) $(obj)/$(XDP_SAMPLE): $(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h +$(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check= -include $(BPF_SAMPLES_PATH)/Makefile.target diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index f83d9f65c65b..d62ab3b77153 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -14,13 +14,44 @@ #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" -#define MAX_SYMS 400000 -static struct ksym syms[MAX_SYMS]; -static int sym_cnt; +static struct ksym *syms; +static size_t sym_cap; +static size_t sym_cnt; + +static int ksyms__add_symbol(const char *name, unsigned long addr) +{ + void *tmp; + + 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); + syms = NULL; + sym_cnt = 0; + sym_cap = 0; +} static int ksym_cmp(const void *p1, const void *p2) { @@ -33,9 +64,7 @@ int load_kallsyms_refresh(void) char func[256], buf[256]; char symbol; void *addr; - int i = 0; - - sym_cnt = 0; + int ret; f = fopen("/proc/kallsyms", "r"); if (!f) @@ -46,17 +75,22 @@ 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 = libbpf_ensure_mem((void **) &syms, &sym_cap, + sizeof(struct ksym), sym_cnt + 1); + if (ret) + goto error; + 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)