Messages in this thread | | | Date | Fri, 3 May 2019 13:12:34 +0100 | From | Qais Yousef <> | Subject | Re: [PATCH RFC] bpf: Add support for reading user pointers |
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Hi Joel
On 05/02/19 16:49, Joel Fernandes (Google) wrote: > The eBPF based opensnoop tool fails to read the file path string passed > to the do_sys_open function. This is because it is a pointer to > userspace address and causes an -EFAULT when read with > probe_kernel_read. This is not an issue when running the tool on x86 but > is an issue on arm64. This patch adds a new bpf function call based
I just did an experiment and if I use Android 4.9 kernel I indeed fail to see PATH info when running opensnoop. But if I run on 5.1-rc7 opensnoop behaves correctly on arm64.
My guess either a limitation that was fixed on later kernel versions or Android kernel has some strict option/modifications that make this fail?
root@buildroot:/# uname -a Linux buildroot 5.1.0-rc7-00164-ga00214620959-dirty #41 SMP PREEMPT Thu May 2 16:33:00 BST 2019 aarch64 GNU/Linux root@buildroot:/# opensnoop PID COMM FD ERR PATH 5180 default.script -1 2 /etc/ld.so.cache 5180 default.script -1 2 /lib/tls/v8l/neon/vfp/libresolv.so.2 5180 default.script -1 2 /lib/tls/v8l/neon/libresolv.so.2 5180 default.script -1 2 /lib/tls/v8l/vfp/libresolv.so.2 5180 default.script -1 2 /lib/tls/v8l/libresolv.so.2 5180 default.script -1 2 /lib/tls/neon/vfp/libresolv.so.2 5180 default.script -1 2 /lib/tls/neon/libresolv.so.2 5180 default.script -1 2 /lib/tls/vfp/libresolv.so.2 5180 default.script -1 2 /lib/tls/libresolv.so.2 5180 default.script -1 2 /lib/v8l/neon/vfp/libresolv.so.2 5180 default.script -1 2 /lib/v8l/neon/libresolv.so.2 5180 default.script -1 2 /lib/v8l/vfp/libresolv.so.2 5180 default.script -1 2 /lib/v8l/libresolv.so.2 5180 default.script -1 2 /lib/neon/vfp/libresolv.so.2 5180 default.script -1 2 /lib/neon/libresolv.so.2 5180 default.script -1 2 /lib/vfp/libresolv.so.2 5180 default.script 3 0 /lib/libresolv.so.2 5180 default.script 3 0 /lib/libc.so.6 5180 default.script 3 0 /usr/share/udhcpc/default.script 5180 default.script 3 0 /usr/share/udhcpc/default.script.d/
-- Qais Yousef
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