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Suppose you have a map array value that is something like this
struct foo {
unsigned iter;
int array[SOME_CONSTANT];
};
You can easily insert this into an array, but you cannot modify the contents of
foo->array[] after the fact. This is because we have no way to verify we won't
go off the end of the array at verification time. This patch provides a start
for this work. We accomplish this by keeping track of a minimum and maximum
value a register could be while we're checking the code. Then at the time we
try to do an access into a MAP_VALUE we verify that the maximum offset into that
region is a valid access into that memory region. So in practice, code such as
this
unsigned index = 0;
if (foo->iter >= SOME_CONSTANT)
foo->iter = index;
else
index = foo->iter++;
foo->array[index] = bar;
would be allowed, as we can verify that index will always be between 0 and
SOME_CONSTANT-1. If you wish to use signed values you'll have to have an extra
check to make sure the index isn't less than 0, or do something like index %=
SOME_CONSTANT.
Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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|---|---|---|
| .. | ||
| bpf_helpers.h | ||
| bpf_load.c | ||
| bpf_load.h | ||
| fds_example.c | ||
| lathist_kern.c | ||
| lathist_user.c | ||
| libbpf.c | ||
| libbpf.h | ||
| Makefile | ||
| map_perf_test_kern.c | ||
| map_perf_test_user.c | ||
| offwaketime_kern.c | ||
| offwaketime_user.c | ||
| parse_ldabs.c | ||
| parse_simple.c | ||
| parse_varlen.c | ||
| README.rst | ||
| sampleip_kern.c | ||
| sampleip_user.c | ||
| sock_example.c | ||
| sockex1_kern.c | ||
| sockex1_user.c | ||
| sockex2_kern.c | ||
| sockex2_user.c | ||
| sockex3_kern.c | ||
| sockex3_user.c | ||
| spintest_kern.c | ||
| spintest_user.c | ||
| tcbpf1_kern.c | ||
| tcbpf2_kern.c | ||
| test_cgrp2_array_pin.c | ||
| test_cgrp2_tc_kern.c | ||
| test_cgrp2_tc.sh | ||
| test_cls_bpf.sh | ||
| test_current_task_under_cgroup_kern.c | ||
| test_current_task_under_cgroup_user.c | ||
| test_ipip.sh | ||
| test_maps.c | ||
| test_overhead_kprobe_kern.c | ||
| test_overhead_tp_kern.c | ||
| test_overhead_user.c | ||
| test_probe_write_user_kern.c | ||
| test_probe_write_user_user.c | ||
| test_tunnel_bpf.sh | ||
| test_verifier.c | ||
| trace_event_kern.c | ||
| trace_event_user.c | ||
| trace_output_kern.c | ||
| trace_output_user.c | ||
| tracex1_kern.c | ||
| tracex1_user.c | ||
| tracex2_kern.c | ||
| tracex2_user.c | ||
| tracex3_kern.c | ||
| tracex3_user.c | ||
| tracex4_kern.c | ||
| tracex4_user.c | ||
| tracex5_kern.c | ||
| tracex5_user.c | ||
| tracex6_kern.c | ||
| tracex6_user.c | ||
| xdp1_kern.c | ||
| xdp1_user.c | ||
| xdp2_kern.c | ||
eBPF sample programs ==================== This directory contains a mini eBPF library, test stubs, verifier test-suite and examples for using eBPF. Build dependencies ================== Compiling requires having installed: * clang >= version 3.4.0 * llvm >= version 3.7.1 Note that LLVM's tool 'llc' must support target 'bpf', list version and supported targets with command: ``llc --version`` Kernel headers -------------- There are usually dependencies to header files of the current kernel. To avoid installing devel kernel headers system wide, as a normal user, simply call:: make headers_install This will creates a local "usr/include" directory in the git/build top level directory, that the make system automatically pickup first. Compiling ========= For building the BPF samples, issue the below command from the kernel top level directory:: make samples/bpf/ Do notice the "/" slash after the directory name. It is also possible to call make from this directory. This will just hide the the invocation of make as above with the appended "/". Manually compiling LLVM with 'bpf' support ------------------------------------------ Since version 3.7.0, LLVM adds a proper LLVM backend target for the BPF bytecode architecture. By default llvm will build all non-experimental backends including bpf. To generate a smaller llc binary one can use:: -DLLVM_TARGETS_TO_BUILD="BPF" Quick sniplet for manually compiling LLVM and clang (build dependencies are cmake and gcc-c++):: $ git clone http://llvm.org/git/llvm.git $ cd llvm/tools $ git clone --depth 1 http://llvm.org/git/clang.git $ cd ..; mkdir build; cd build $ cmake .. -DLLVM_TARGETS_TO_BUILD="BPF;X86" $ make -j $(getconf _NPROCESSORS_ONLN) It is also possible to point make to the newly compiled 'llc' or 'clang' command via redefining LLC or CLANG on the make command line:: make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang