The BPF implementation of RV monitors cannot use standard reactors in the kernel and currently reactions are skipped.
Add rv_react() to build the printk format using BPF macros and pass that to a BPF function with a single message parameter, since BPF doesn't support variable arguments. This function is defined as weak, so the rv tool can link a different implementation on top at load time. Implement a printk reactor that is simply reimplementing this function passing the message to bpf_printk(). Signed-off-by: Gabriele Monaco <[email protected]> --- include/rv/da_monitor.h | 4 +- tools/verification/rv/Makefile | 12 ++- tools/verification/rv/Makefile.rv | 5 + .../rv/bpf_monitors/da_monitor_bpf.h | 12 ++- tools/verification/rv/bpf_reactors/.gitignore | 2 + tools/verification/rv/bpf_reactors/panic.c | 15 +++ tools/verification/rv/bpf_reactors/printk.c | 13 +++ tools/verification/rv/src/bpf_monitor.c | 102 +++++++++++++++++- 8 files changed, 157 insertions(+), 8 deletions(-) create mode 100644 tools/verification/rv/bpf_reactors/.gitignore create mode 100644 tools/verification/rv/bpf_reactors/panic.c create mode 100644 tools/verification/rv/bpf_reactors/printk.c diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h index ee1cec73ec85..28cff26aecfe 100644 --- a/include/rv/da_monitor.h +++ b/include/rv/da_monitor.h @@ -84,7 +84,8 @@ static struct rv_monitor rv_this; #ifdef __BPF__ #include "da_monitor_bpf.h" -#else +#endif + static void react(enum states curr_state, enum events event) { rv_react(&rv_this, @@ -93,7 +94,6 @@ static void react(enum states curr_state, enum events event) model_get_event_name(event), model_get_state_name(curr_state)); } -#endif /* * da_monitor_reset_state - reset a monitor and setting it to init state diff --git a/tools/verification/rv/Makefile b/tools/verification/rv/Makefile index bb81593acd71..44b0e3af1488 100644 --- a/tools/verification/rv/Makefile +++ b/tools/verification/rv/Makefile @@ -73,8 +73,11 @@ static: $(RV_IN) $(QUIET_LINK)$(CC) $(LDFLAGS) -o $(RV)-static $(RV_IN) $(EXTLIBS) BPF_DIR := bpf_monitors +BPF_REACT_DIR := bpf_reactors BPF_SOURCES := $(wildcard $(BPF_DIR)/*.c) BPF_OBJECTS := $(BPF_SOURCES:.c=.o) +BPF_REACT_SOURCES := $(wildcard $(BPF_REACT_DIR)/*.c) +BPF_REACT_OBJECTS := $(BPF_REACT_SOURCES:.c=.o) VMLINUX_H := $(BPF_DIR)/vmlinux.h BPF_INCLUDES := -I$(srctree)/include/uapi @@ -95,9 +98,14 @@ $(BPF_DIR)/%.o: $(BPF_DIR)/%.c $(VMLINUX_H) $(Q)$(LLVM_STRIP) -g $@ $(Q)$(LLVM_OBJCOPY) --remove-section=.rel.rodata $@ --include $(BPF_SOURCES:.c=.d) +$(BPF_REACT_DIR)/%.o: $(BPF_REACT_DIR)/%.c $(VMLINUX_H) + $(QUIET_CLANG)$(CLANG) $(BPF_CFLAGS) -c $< -o $@ + $(Q)$(LLVM_STRIP) -g $@ + $(Q)$(LLVM_OBJCOPY) --remove-section=.rel.rodata $@ + +-include $(BPF_SOURCES:.c=.d) $(BPF_REACT_SOURCES:.c=.d) -bpf: $(BPF_OBJECTS) +bpf: $(BPF_OBJECTS) $(BPF_REACT_OBJECTS) rv.%: fixdep FORCE make -f $(srctree)/tools/build/Makefile.build dir=. $@ diff --git a/tools/verification/rv/Makefile.rv b/tools/verification/rv/Makefile.rv index 418748bc3aa1..3ac329851914 100644 --- a/tools/verification/rv/Makefile.rv +++ b/tools/verification/rv/Makefile.rv @@ -34,6 +34,7 @@ MKDIR := mkdir STRIP := strip BINDIR := /usr/bin BPF_MON_DIR := /usr/share/rv/bpf_monitors +BPF_REACT_DIR := /usr/share/rv/bpf_reactors .PHONY: install install: doc_install @@ -44,6 +45,10 @@ ifneq ($(wildcard bpf_monitors/*.o),) $(Q)$(MKDIR) -p $(DESTDIR)$(BPF_MON_DIR) $(call QUIET_INSTALL,bpf_monitors)$(INSTALL) bpf_monitors/*.o -m 644 $(DESTDIR)$(BPF_MON_DIR) endif +ifneq ($(wildcard bpf_reactors/*.o),) + $(Q)$(MKDIR) -p $(DESTDIR)$(BPF_REACT_DIR) + $(call QUIET_INSTALL,bpf_reactors)$(INSTALL) bpf_reactors/*.o -m 644 $(DESTDIR)$(BPF_REACT_DIR) +endif .PHONY: doc doc_clean doc_install doc: diff --git a/tools/verification/rv/bpf_monitors/da_monitor_bpf.h b/tools/verification/rv/bpf_monitors/da_monitor_bpf.h index 12f0f78b9c9d..a37d11fef6f1 100644 --- a/tools/verification/rv/bpf_monitors/da_monitor_bpf.h +++ b/tools/verification/rv/bpf_monitors/da_monitor_bpf.h @@ -17,7 +17,6 @@ #include "bpf_atomic.h" /* BPF monitors don't support these */ -#define rv_react(...) do {} while (0) #define trace_rv_retries_error(...) do {} while (0) #define pr_warn(fmt, ...) bpf_printk(fmt, ##__VA_ARGS__) #define rv_monitoring_on() 1 @@ -75,8 +74,15 @@ static const struct rv_trace_entry __used *_btf_trace; static inline void da_monitor_reset(struct da_monitor *da_mon); -/* BPF monitors do not use reactors */ -static inline void react(enum states curr_state, enum events event) { } +__noinline __weak void bpf_rv_react(char *msg) { } + +#define rv_react(mon, fmt, ...) \ + ({ \ + char ___msg[256]; \ + \ + if (BPF_SNPRINTF(___msg, sizeof(___msg), fmt, ##__VA_ARGS__) > 0) \ + bpf_rv_react(___msg); \ + }) /* * BPF monitor implementations diff --git a/tools/verification/rv/bpf_reactors/.gitignore b/tools/verification/rv/bpf_reactors/.gitignore new file mode 100644 index 000000000000..e5add9141ef5 --- /dev/null +++ b/tools/verification/rv/bpf_reactors/.gitignore @@ -0,0 +1,2 @@ +*.d +vmlinux.h diff --git a/tools/verification/rv/bpf_reactors/panic.c b/tools/verification/rv/bpf_reactors/panic.c new file mode 100644 index 000000000000..775f91a300f0 --- /dev/null +++ b/tools/verification/rv/bpf_reactors/panic.c @@ -0,0 +1,15 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> + +void bpf_rv_react(char *msg) +{ + struct pt_regs regs = { 0 }; + + crash_kexec(®s); +} + +char LICENSE[] SEC("license") = "GPL"; +static char DESCRIPTION[] SEC(".rodata.description") = + "panic the system if an exception is found."; diff --git a/tools/verification/rv/bpf_reactors/printk.c b/tools/verification/rv/bpf_reactors/printk.c new file mode 100644 index 000000000000..580410d2a1fc --- /dev/null +++ b/tools/verification/rv/bpf_reactors/printk.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> + +void bpf_rv_react(char *msg) +{ + bpf_printk("%s", msg); +} + +char LICENSE[] SEC("license") = "GPL"; +static char DESCRIPTION[] SEC(".rodata.description") = + "prints the exception msg to the trace buffer."; diff --git a/tools/verification/rv/src/bpf_monitor.c b/tools/verification/rv/src/bpf_monitor.c index d43ee75d3904..35bd1f40a109 100644 --- a/tools/verification/rv/src/bpf_monitor.c +++ b/tools/verification/rv/src/bpf_monitor.c @@ -5,6 +5,7 @@ * Copyright (C) 2026 Red Hat Inc, Gabriele Monaco <[email protected]> */ +#define _GNU_SOURCE #include <stdio.h> #include <stdlib.h> #include <string.h> @@ -14,6 +15,7 @@ #include <libgen.h> #include <errno.h> #include <inttypes.h> +#include <sys/mman.h> #include <bpf/libbpf.h> #include <bpf/bpf.h> #include <bpf/btf.h> @@ -36,6 +38,7 @@ static char bpf_base_paths[][MAX_PATH] = { #define MAX_ENUMS 64 #define MAX_LINKS 16 #define PROG_ENABLE_MON "enable_monitor" +#define BPF_REACTOR "bpf_rv_react" #define RV_TRACE_STRUCT "rv_trace_entry" #define RV_TRACE_TYPE_ENUM "rv_trace_type" @@ -676,12 +679,31 @@ static struct ring_buffer *bpf_setup_ring_buffer(struct bpf_object *obj, return rb; } +static void list_reactor_action(const char *name, struct bpf_object *obj) +{ + const struct btf *btf = bpf_object__btf(obj); + + if (btf__find_by_name_kind(btf, BPF_REACTOR, BTF_KIND_FUNC) >= 0) + fprintf(stderr, "%s ", name); +} + +/* + * list_reactors_from_path - list reactors from a specific base path + */ +static void list_reactors_from_path(const char *base_path) +{ + bpf_object_iterate_path(base_path, "bpf_reactors", list_reactor_action); +} + /* * bpf_usage_print_reactors - print available BPF reactors */ void bpf_usage_print_reactors(void) { - fprintf(stderr, " available BPF reactors: nop\n"); + fprintf(stderr, " available BPF reactors: nop "); + for (int i = 0; bpf_base_paths[i][0]; i++) + list_reactors_from_path(bpf_base_paths[i]); + fprintf(stderr, "\n"); } /* @@ -720,6 +742,7 @@ static struct bpf_object *open_bpf_monitor(const char *path, struct bpf_monitor_ int res; LIBBPF_OPTS(bpf_object_open_opts, opts, + .object_name = ctx->monitor_name, /* Define statically as arch is known, Kconfig may not be available */ #ifdef __x86_64__ .kconfig = "CONFIG_X86_64=y\n", @@ -795,6 +818,65 @@ static int attach_bpf_handlers(const char *monitor_name, struct bpf_object *obj, return enable_mon_fd; } +static int find_bpf_reactor(const char *reactor_name, char *path_out, size_t path_len) +{ + return find_bpf_file("bpf_reactors", reactor_name, path_out, path_len); +} + +/* + * link_bpf_reactor - link the reactor function to the monitor + * + * Reactors are objects defining the BPF_REACTOR function, link that over the + * weak definition present in the monitor and return a file descriptor to the + * final linked object in memory. + * + * Returns memfd of final object on success, -1 on error. + */ +static int link_bpf_reactor(const char *monitor_path, const char *reactor_path) +{ + struct bpf_linker *linker = NULL; + int memfd = -1; + int err = 0; + + memfd = memfd_create("linked_bpf", 0); + if (memfd < 0) { + err_msg("bpf: failed to create memfd: %s\n", strerror(errno)); + return -1; + } + + linker = bpf_linker__new_fd(memfd, NULL); + if (!linker) { + err_msg("bpf: failed to create BPF linker\n"); + goto out; + } + + err = bpf_linker__add_file(linker, monitor_path, NULL); + if (err) { + err_msg("bpf: failed to add monitor file to linker: %s\n", strerror(-err)); + goto out; + } + + err = bpf_linker__add_file(linker, reactor_path, NULL); + if (err) { + err_msg("bpf: failed to add reactor file to linker: %s\n", strerror(-err)); + goto out; + } + + err = bpf_linker__finalize(linker); + if (err) { + err_msg("bpf: failed to finalize BPF linker: %s\n", strerror(-err)); + goto out; + } + + bpf_linker__free(linker); + return memfd; + +out: + bpf_linker__free(linker); + close(memfd); + return -1; +} + /* * bpf_run_monitor - load and run a BPF monitor * @@ -808,6 +890,7 @@ int bpf_run_monitor(char *monitor_name, int argc, char **argv) struct bpf_object *obj = NULL; int res, link_count = 0, enable_mon_fd, retval = -1; char monitor_path[MAX_PATH]; + int memfd = -1; libbpf_set_print(libbpf_print_fn); bpf_fill_base_paths(); @@ -830,8 +913,25 @@ int bpf_run_monitor(char *monitor_name, int argc, char **argv) strncpy(ctx.monitor_name, monitor_name, sizeof(ctx.monitor_name) - 1); + if (config.reactor && strcmp(config.reactor, "nop")) { + char reactor_path[MAX_PATH]; + + if (!find_bpf_reactor(config.reactor, reactor_path, sizeof(reactor_path))) { + mon_usage(1, monitor_name, + "bpf: failed to set %s reactor, is it available?", + config.reactor); + goto cleanup; + } + + memfd = link_bpf_reactor(monitor_path, reactor_path); + if (memfd < 0) + goto cleanup; + + snprintf(monitor_path, sizeof(monitor_path), "/proc/self/fd/%d", memfd); + } obj = open_bpf_monitor(monitor_path, &ctx); + close(memfd); if (!obj) goto cleanup; -- 2.55.0
