| Message ID | 20220206043107.18549-3-houtao1@huawei.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | selftests: add test for kfunc call | expand |
On 2/5/22 8:31 PM, Hou Tao wrote: > In add_kfunc_call(), bpf_kfunc_desc->imm with type s32 is used to > represent the offset of called kfunc from __bpf_call_base, so > add a test to ensure that the offset will not be overflowed. > > Signed-off-by: Hou Tao <houtao1@huawei.com> > --- > .../selftests/bpf/prog_tests/ksyms_module.c | 42 +++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c > index a1ebac70ec29..8055fbbf720b 100644 > --- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c > +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c > @@ -3,9 +3,49 @@ > > #include <test_progs.h> > #include <network_helpers.h> > +#include <trace_helpers.h> > #include "test_ksyms_module.lskel.h" > #include "test_ksyms_module.skel.h" > > +/* > + * Check whether or not s32 in bpf_kfunc_desc is sufficient > + * to represent the offset between bpf_testmod_test_mod_kfunc > + * and __bpf_call_base. > + */ > +static void test_ksyms_module_valid_offset(void) > +{ > + struct test_ksyms_module *skel; > + unsigned long long kfunc_addr; > + unsigned long long base_addr; > + long long actual_offset; > + int used_offset; > + int err; > + > + if (!env.has_testmod) { > + test__skip(); > + return; > + } > + > + /* Ensure kfunc call is supported */ > + skel = test_ksyms_module__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open")) > + return; > + > + err = kallsyms_find("bpf_testmod_test_mod_kfunc", &kfunc_addr); > + if (!ASSERT_OK(err, "find kfunc addr")) > + goto cleanup; > + > + err = kallsyms_find("__bpf_call_base", &base_addr); > + if (!ASSERT_OK(err, "find base addr")) > + goto cleanup; > + > + used_offset = kfunc_addr - base_addr; > + actual_offset = kfunc_addr - base_addr; > + ASSERT_EQ((long long)used_offset, actual_offset, "kfunc offset overflowed"); I am a little bit confused about motivation here. Maybe I missed something. If we indeed have kfunc offset overflow, should kernel verifier just reject the program? Specially, we should make the above test_ksyms_module__open_and_load() fail? > +cleanup: > + test_ksyms_module__destroy(skel); > +} > + > static void test_ksyms_module_lskel(void) > { > struct test_ksyms_module_lskel *skel; > @@ -62,6 +102,8 @@ static void test_ksyms_module_libbpf(void) > > void test_ksyms_module(void) > { > + if (test__start_subtest("valid_offset")) > + test_ksyms_module_valid_offset(); > if (test__start_subtest("lskel")) > test_ksyms_module_lskel(); > if (test__start_subtest("libbpf"))
Hi, On 2/8/2022 2:33 AM, Yonghong Song wrote: > > > On 2/5/22 8:31 PM, Hou Tao wrote: >> In add_kfunc_call(), bpf_kfunc_desc->imm with type s32 is used to >> represent the offset of called kfunc from __bpf_call_base, so >> add a test to ensure that the offset will not be overflowed. >> >> Signed-off-by: Hou Tao <houtao1@huawei.com> >> --- >> .../selftests/bpf/prog_tests/ksyms_module.c | 42 +++++++++++++++++++ >> 1 file changed, 42 insertions(+) >> [...] >> + /* Ensure kfunc call is supported */ >> + skel = test_ksyms_module__open_and_load(); >> + if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open")) >> + return; >> + >> + err = kallsyms_find("bpf_testmod_test_mod_kfunc", &kfunc_addr); >> + if (!ASSERT_OK(err, "find kfunc addr")) >> + goto cleanup; >> + >> + err = kallsyms_find("__bpf_call_base", &base_addr); >> + if (!ASSERT_OK(err, "find base addr")) >> + goto cleanup; >> + >> + used_offset = kfunc_addr - base_addr; >> + actual_offset = kfunc_addr - base_addr; >> + ASSERT_EQ((long long)used_offset, actual_offset, "kfunc offset >> overflowed"); > > I am a little bit confused about motivation here. Maybe I missed something. If > we indeed have kfunc offset overflow, > should kernel verifier just reject the program? Specially, > we should make the above test_ksyms_module__open_and_load() > fail? In add_kfunc_call(), the calculation of imm doesn't consider the overflow of s32. So test_ksyms_module__open_and_load() will succeed. I think the better solution is to put the overflow check in add_kfunc_call(), so will drop this patch and add the overflow check in add_kfunc_call() instead. Regards, Tao [...]
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c index a1ebac70ec29..8055fbbf720b 100644 --- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c @@ -3,9 +3,49 @@ #include <test_progs.h> #include <network_helpers.h> +#include <trace_helpers.h> #include "test_ksyms_module.lskel.h" #include "test_ksyms_module.skel.h" +/* + * Check whether or not s32 in bpf_kfunc_desc is sufficient + * to represent the offset between bpf_testmod_test_mod_kfunc + * and __bpf_call_base. + */ +static void test_ksyms_module_valid_offset(void) +{ + struct test_ksyms_module *skel; + unsigned long long kfunc_addr; + unsigned long long base_addr; + long long actual_offset; + int used_offset; + int err; + + if (!env.has_testmod) { + test__skip(); + return; + } + + /* Ensure kfunc call is supported */ + skel = test_ksyms_module__open_and_load(); + if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open")) + return; + + err = kallsyms_find("bpf_testmod_test_mod_kfunc", &kfunc_addr); + if (!ASSERT_OK(err, "find kfunc addr")) + goto cleanup; + + err = kallsyms_find("__bpf_call_base", &base_addr); + if (!ASSERT_OK(err, "find base addr")) + goto cleanup; + + used_offset = kfunc_addr - base_addr; + actual_offset = kfunc_addr - base_addr; + ASSERT_EQ((long long)used_offset, actual_offset, "kfunc offset overflowed"); +cleanup: + test_ksyms_module__destroy(skel); +} + static void test_ksyms_module_lskel(void) { struct test_ksyms_module_lskel *skel; @@ -62,6 +102,8 @@ static void test_ksyms_module_libbpf(void) void test_ksyms_module(void) { + if (test__start_subtest("valid_offset")) + test_ksyms_module_valid_offset(); if (test__start_subtest("lskel")) test_ksyms_module_lskel(); if (test__start_subtest("libbpf"))
In add_kfunc_call(), bpf_kfunc_desc->imm with type s32 is used to represent the offset of called kfunc from __bpf_call_base, so add a test to ensure that the offset will not be overflowed. Signed-off-by: Hou Tao <houtao1@huawei.com> --- .../selftests/bpf/prog_tests/ksyms_module.c | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+)