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Commit 86df959a authored by Connor O'Brien's avatar Connor O'Brien
Browse files

libtimeinstate: open maps write-only 



Userspace never reads from these maps, so we can reduce the needed
permissions by opening them write-only

Test: libtimeinstate_test passes
Bug: 138317993
Change-Id: Icbd87b35dc93992e6542ae04ac1ea733b274d28a
Signed-off-by: default avatarConnor O'Brien <connoro@google.com>
parent 8e7f193b

libs/cputimeinstate/cputimeinstate.cpp

+12 −2
Original line number Diff line number Diff line
@@ -85,6 +85,16 @@ static int comparePolicyFiles(const struct dirent **d1, const struct dirent **d2 
    return policyN1 - policyN2;

}



static int bpf_obj_get_wronly(const char *pathname) {

    union bpf_attr attr;



    memset(&attr, 0, sizeof(attr));

    attr.pathname = ptr_to_u64((void *)pathname);

    attr.file_flags = BPF_F_WRONLY;



    return syscall(__NR_bpf, BPF_OBJ_GET, &attr, sizeof(attr));

}



static bool initGlobals() {

    std::lock_guard<std::mutex> guard(gInitializedMutex);

    if (gInitialized) return true;
@@ -153,7 +163,7 @@ static bool attachTracepointProgram(const std::string &eventType, const std::str 
bool startTrackingUidTimes() {

    if (!initGlobals()) return false;



    unique_fd fd(bpf_obj_get(BPF_FS_PATH "map_time_in_state_cpu_policy_map"));

    unique_fd fd(bpf_obj_get_wronly(BPF_FS_PATH "map_time_in_state_cpu_policy_map"));

    if (fd < 0) return false;



    for (uint32_t i = 0; i < gPolicyCpus.size(); ++i) {
@@ -162,7 +172,7 @@ bool startTrackingUidTimes() { 
        }

    }



    unique_fd fd2(bpf_obj_get(BPF_FS_PATH "map_time_in_state_freq_to_idx_map"));

    unique_fd fd2(bpf_obj_get_wronly(BPF_FS_PATH "map_time_in_state_freq_to_idx_map"));

    if (fd2 < 0) return false;

    freq_idx_key_t key;

    for (uint32_t i = 0; i < gNPolicies; ++i) {