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Subject[PATCH v3 bpf-next 14/21] selftests/bpf: Test file_pos field in bpf_sysctl ctx
Date
Test access to file_pos field of bpf_sysctl context, both read (incl.
narrow read) and write.

# ./test_sysctl
...
Test case: ctx:file_pos sysctl:read read ok .. [PASS]
Test case: ctx:file_pos sysctl:read read ok narrow .. [PASS]
Test case: ctx:file_pos sysctl:read write ok .. [PASS]
...

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
tools/testing/selftests/bpf/test_sysctl.c | 64 +++++++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
index 95437b72404f..43008aae32d3 100644
--- a/tools/testing/selftests/bpf/test_sysctl.c
+++ b/tools/testing/selftests/bpf/test_sysctl.c
@@ -30,6 +30,7 @@ struct sysctl_test {
const char *sysctl;
int open_flags;
const char *newval;
+ const char *oldval;
enum {
LOAD_REJECT,
ATTACH_REJECT,
@@ -130,6 +131,64 @@ static struct sysctl_test tests[] = {
.open_flags = O_RDONLY,
.result = LOAD_REJECT,
},
+ {
+ .descr = "ctx:file_pos sysctl:read read ok",
+ .insns = {
+ /* If (file_pos == X) */
+ BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, file_pos)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0, 2),
+
+ /* return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_JMP_A(1),
+
+ /* else return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "ctx:file_pos sysctl:read read ok narrow",
+ .insns = {
+ /* If (file_pos == X) */
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, file_pos)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0, 2),
+
+ /* return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_JMP_A(1),
+
+ /* else return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "ctx:file_pos sysctl:read write ok",
+ .insns = {
+ /* file_pos = X */
+ BPF_MOV64_IMM(BPF_REG_0, 2),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct bpf_sysctl, file_pos)),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .oldval = "nux\n",
+ .result = SUCCESS,
+ },
{
.descr = "sysctl_get_name sysctl_value:base ok",
.insns = {
@@ -848,6 +907,11 @@ static int access_sysctl(const char *sysctl_path,

if (read(fd, buf, sizeof(buf)) == -1)
goto err;
+ if (test->oldval &&
+ strncmp(buf, test->oldval, strlen(test->oldval))) {
+ log_err("Read value %s != %s", buf, test->oldval);
+ goto err;
+ }
} else if (test->open_flags == O_WRONLY) {
if (!test->newval) {
log_err("New value for sysctl is not set");
--
2.17.1
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