* [PATCH bpf-next v2 0/2] bpf, arm64: enable kfunc call
@ 2022-01-27 7:15 Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 1/2] " Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset Hou Tao
0 siblings, 2 replies; 4+ messages in thread
From: Hou Tao @ 2022-01-27 7:15 UTC (permalink / raw)
To: Daniel Borkmann
Cc: Alexei Starovoitov, Martin KaFai Lau, Yonghong Song,
Andrii Nakryiko, David S . Miller, Jakub Kicinski,
John Fastabend, netdev, bpf, houtao1, Zi Shen Lim,
Catalin Marinas, Will Deacon, Ard Biesheuvel, linux-arm-kernel
Hi,
The simple patchset tries to enable kfunc call for arm64. Patch #1 just
overrides bpf_jit_supports_kfunc_call() to enable kfunc call and patch #2
add a test to ensure s32 is sufficient for kfunc offset.
Change Log:
v2:
* add a test to check whether imm will be overflowed for kfunc call
v1: https://lore.kernel.org/bpf/20220119144942.305568-1-houtao1@huawei.com
Hou Tao (2):
bpf, arm64: enable kfunc call
selftests/bpf: check whether s32 is sufficient for kfunc offset
arch/arm64/net/bpf_jit_comp.c | 5 ++
.../selftests/bpf/prog_tests/ksyms_module.c | 72 +++++++++++++++++++
2 files changed, 77 insertions(+)
--
2.27.0
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH bpf-next v2 1/2] bpf, arm64: enable kfunc call
2022-01-27 7:15 [PATCH bpf-next v2 0/2] bpf, arm64: enable kfunc call Hou Tao
@ 2022-01-27 7:15 ` Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset Hou Tao
1 sibling, 0 replies; 4+ messages in thread
From: Hou Tao @ 2022-01-27 7:15 UTC (permalink / raw)
To: Daniel Borkmann
Cc: Alexei Starovoitov, Martin KaFai Lau, Yonghong Song,
Andrii Nakryiko, David S . Miller, Jakub Kicinski,
John Fastabend, netdev, bpf, houtao1, Zi Shen Lim,
Catalin Marinas, Will Deacon, Ard Biesheuvel, linux-arm-kernel
Since commit b2eed9b58811 ("arm64/kernel: kaslr: reduce module
randomization range to 2 GB"), for arm64 whether KASLR is enabled
or not, the module is placed within 2GB of the kernel region, so
s32 in bpf_kfunc_desc is sufficient to represente the offset of
module function relative to __bpf_call_base. The only thing needed
is to override bpf_jit_supports_kfunc_call().
Signed-off-by: Hou Tao <houtao1@huawei.com>
---
arch/arm64/net/bpf_jit_comp.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 6d92f363028c..e60c464004c2 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1284,6 +1284,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
return prog;
}
+bool bpf_jit_supports_kfunc_call(void)
+{
+ return true;
+}
+
u64 bpf_jit_alloc_exec_limit(void)
{
return VMALLOC_END - VMALLOC_START;
--
2.27.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset
2022-01-27 7:15 [PATCH bpf-next v2 0/2] bpf, arm64: enable kfunc call Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 1/2] " Hou Tao
@ 2022-01-27 7:15 ` Hou Tao
2022-01-28 14:42 ` Daniel Borkmann
1 sibling, 1 reply; 4+ messages in thread
From: Hou Tao @ 2022-01-27 7:15 UTC (permalink / raw)
To: Daniel Borkmann
Cc: Alexei Starovoitov, Martin KaFai Lau, Yonghong Song,
Andrii Nakryiko, David S . Miller, Jakub Kicinski,
John Fastabend, netdev, bpf, houtao1, Zi Shen Lim,
Catalin Marinas, Will Deacon, Ard Biesheuvel, linux-arm-kernel
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 | 72 +++++++++++++++++++
1 file changed, 72 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
index d490ad80eccb..ce0cd3446931 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
@@ -6,6 +6,76 @@
#include "test_ksyms_module.lskel.h"
#include "test_ksyms_module.skel.h"
+/* Most logic comes from bpf_object__read_kallsyms_file() */
+static int test_find_func_in_kallsyms(const char *func, unsigned long *addr)
+{
+ /* Same as KSYM_NAME_LEN */
+ char sym_name[128];
+ char sym_type;
+ unsigned long sym_addr;
+ int ret, err;
+ FILE *f;
+
+ f = fopen("/proc/kallsyms", "r");
+ if (!f)
+ return -errno;
+
+ err = -ENOENT;
+ while (true) {
+ ret = fscanf(f, "%lx %c %127s%*[^\n]\n",
+ &sym_addr, &sym_type, sym_name);
+ if (ret == EOF && feof(f))
+ break;
+
+ if (ret != 3) {
+ err = -EINVAL;
+ break;
+ }
+
+ if ((sym_type == 't' || sym_type == 'T') &&
+ !strcmp(sym_name, func)) {
+ *addr = sym_addr;
+ err = 0;
+ break;
+ }
+ }
+
+ fclose(f);
+ return err;
+}
+
+/*
+ * 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.
+ */
+void test_ksyms_module_valid_offset(void)
+{
+ unsigned long kfunc_addr;
+ unsigned long base_addr;
+ int used_offset;
+ long actual_offset;
+ int err;
+
+ if (!env.has_testmod) {
+ test__skip();
+ return;
+ }
+
+ err = test_find_func_in_kallsyms("bpf_testmod_test_mod_kfunc",
+ &kfunc_addr);
+ if (!ASSERT_OK(err, "find kfunc addr"))
+ return;
+
+ err = test_find_func_in_kallsyms("__bpf_call_base", &base_addr);
+ if (!ASSERT_OK(err, "find base addr"))
+ return;
+
+ used_offset = kfunc_addr - base_addr;
+ actual_offset = kfunc_addr - base_addr;
+ ASSERT_EQ((long)used_offset, actual_offset, "kfunc offset overflowed");
+}
+
void test_ksyms_module_lskel(void)
{
struct test_ksyms_module_lskel *skel;
@@ -55,6 +125,8 @@ 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"))
--
2.27.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset
2022-01-27 7:15 ` [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset Hou Tao
@ 2022-01-28 14:42 ` Daniel Borkmann
0 siblings, 0 replies; 4+ messages in thread
From: Daniel Borkmann @ 2022-01-28 14:42 UTC (permalink / raw)
To: Hou Tao
Cc: Alexei Starovoitov, Martin KaFai Lau, Yonghong Song,
Andrii Nakryiko, David S . Miller, Jakub Kicinski,
John Fastabend, netdev, bpf, Zi Shen Lim, Catalin Marinas,
Will Deacon, Ard Biesheuvel, linux-arm-kernel
On 1/27/22 8:15 AM, 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>
Thanks for looking into this!
> ---
> .../selftests/bpf/prog_tests/ksyms_module.c | 72 +++++++++++++++++++
> 1 file changed, 72 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> index d490ad80eccb..ce0cd3446931 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
> @@ -6,6 +6,76 @@
> #include "test_ksyms_module.lskel.h"
> #include "test_ksyms_module.skel.h"
>
> +/* Most logic comes from bpf_object__read_kallsyms_file() */
> +static int test_find_func_in_kallsyms(const char *func, unsigned long *addr)
> +{
> + /* Same as KSYM_NAME_LEN */
> + char sym_name[128];
> + char sym_type;
> + unsigned long sym_addr;
> + int ret, err;
> + FILE *f;
> +
> + f = fopen("/proc/kallsyms", "r");
> + if (!f)
> + return -errno;
> +
> + err = -ENOENT;
> + while (true) {
> + ret = fscanf(f, "%lx %c %127s%*[^\n]\n",
> + &sym_addr, &sym_type, sym_name);
> + if (ret == EOF && feof(f))
> + break;
> +
> + if (ret != 3) {
> + err = -EINVAL;
> + break;
> + }
> +
> + if ((sym_type == 't' || sym_type == 'T') &&
> + !strcmp(sym_name, func)) {
> + *addr = sym_addr;
> + err = 0;
> + break;
> + }
> + }
> +
> + fclose(f);
> + return err;
> +}
Could we just reuse kallsyms_find() from trace_helpers.c which is also used
in couple of other prog_tests already?
> +
> +/*
> + * 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.
> + */
> +void test_ksyms_module_valid_offset(void)
> +{
> + unsigned long kfunc_addr;
> + unsigned long base_addr;
> + int used_offset;
> + long actual_offset;
> + int err;
> +
> + if (!env.has_testmod) {
> + test__skip();
> + return;
> + }
> +
> + err = test_find_func_in_kallsyms("bpf_testmod_test_mod_kfunc",
> + &kfunc_addr);
> + if (!ASSERT_OK(err, "find kfunc addr"))
> + return;
> +
> + err = test_find_func_in_kallsyms("__bpf_call_base", &base_addr);
> + if (!ASSERT_OK(err, "find base addr"))
> + return;
> +
> + used_offset = kfunc_addr - base_addr;
> + actual_offset = kfunc_addr - base_addr;
> + ASSERT_EQ((long)used_offset, actual_offset, "kfunc offset overflowed");
Is the above also executed in case bpf_jit_supports_kfunc_call() falls back to
the default __weak callback, returning false? If yes, then the ASSERT_EQ() may
fail on archs like s390, ppc, etc where the offset may not be enough.
> +}
> +
> void test_ksyms_module_lskel(void)
> {
> struct test_ksyms_module_lskel *skel;
> @@ -55,6 +125,8 @@ 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"))
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-01-27 7:15 [PATCH bpf-next v2 0/2] bpf, arm64: enable kfunc call Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 1/2] " Hou Tao
2022-01-27 7:15 ` [PATCH bpf-next v2 2/2] selftests/bpf: check whether s32 is sufficient for kfunc offset Hou Tao
2022-01-28 14:42 ` Daniel Borkmann
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