Messages in this thread Patch in this message | | | Date | Wed, 2 Nov 2022 21:54:32 -0700 | Subject | [PATCH v1 2/7] perf trace: Etcsnoop fix libbpf 1.0+ compatibility | From | Ian Rogers <> |
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Don't use deprecated and now broken map style. Avoid use of tools/perf/include/bpf/bpf.h and use the more regular BPF headers. Add "< 0" checks to fix BPF verifier failures about potentially negative values being passed to bpf_perf_event_output. Add a raw_syscalls:sys_enter to avoid the evlist being empty and causing perf trace to exit during argument parsing.
Signed-off-by: Ian Rogers <irogers@google.com> --- tools/perf/examples/bpf/etcsnoop.c | 41 ++++++++++++++++++++++++------ 1 file changed, 33 insertions(+), 8 deletions(-)
diff --git a/tools/perf/examples/bpf/etcsnoop.c b/tools/perf/examples/bpf/etcsnoop.c index e81b535346c0..a04109d9b2b5 100644 --- a/tools/perf/examples/bpf/etcsnoop.c +++ b/tools/perf/examples/bpf/etcsnoop.c @@ -5,7 +5,7 @@ * * Test it with: * - * perf trace -e tools/perf/examples/bpf/augmented_syscalls.c cat /etc/passwd > /dev/null + * perf trace -e tools/perf/examples/bpf/etcsnoop.c cat /etc/passwd > /dev/null * * It'll catch some openat syscalls related to the dynamic linked and * the last one should be the one for '/etc/passwd'. @@ -19,10 +19,17 @@ * tools/perf/include/bpf/stdio.h. */ -#include <stdio.h> +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> /* bpf-output associated map */ -bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__); +struct __augmented_syscalls__ { + __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY); + __type(key, int); + __type(value, __u32); + __uint(max_entries, __NR_CPUS__); +} __augmented_syscalls__ SEC(".maps"); + struct augmented_filename { int size; @@ -30,6 +37,9 @@ struct augmented_filename { char value[64]; }; +#define syscall_enter(name) \ + SEC("!syscalls:sys_enter_" #name) syscall_enter_ ## name + #define augmented_filename_syscall_enter(syscall) \ struct augmented_enter_##syscall##_args { \ struct syscall_enter_##syscall##_args args; \ @@ -39,17 +49,25 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \ { \ char etc[6] = "/etc/"; \ struct augmented_enter_##syscall##_args augmented_args = { .filename.reserved = 0, }; \ - probe_read(&augmented_args.args, sizeof(augmented_args.args), args); \ - augmented_args.filename.size = probe_read_str(&augmented_args.filename.value, \ + long size; \ + \ + if (bpf_probe_read(&augmented_args.args, sizeof(augmented_args.args), args) < 0) \ + return -1; \ + \ + size = bpf_probe_read_str(&augmented_args.filename.value, \ sizeof(augmented_args.filename.value), \ args->filename_ptr); \ + if (size < 0) \ + return -1; \ + \ + augmented_args.filename.size = size; \ if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0) \ return 0; \ /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ \ - return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ + return bpf_perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ &augmented_args, \ (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \ - augmented_args.filename.size)); \ + size)); \ } struct syscall_enter_openat_args { @@ -73,4 +91,11 @@ struct syscall_enter_open_args { augmented_filename_syscall_enter(open); -license(GPL); +struct syscall_enter_args; + +SEC("raw_syscalls:sys_enter") +int sys_enter(struct syscall_enter_args *args) +{ + return 0; +} +char _license[] SEC("license") = "GPL"; -- 2.38.1.273.g43a17bfeac-goog
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