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| author | Alexei Starovoitov <ast@kernel.org> | 2024-01-13 01:01:34 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2024-01-24 01:40:23 +0300 |
| commit | 49c06547d5218b54fbcc6011864b8c8e3aa0b565 (patch) | |
| tree | 16ac97b8b9e0c296cdffe5603c10c33cd7b52665 /tools/testing/selftests/bpf/bpf_experimental.h | |
| parent | 88031b929c01fe3686d34a848c413c2e51e6a7c8 (diff) | |
| download | linux-49c06547d5218b54fbcc6011864b8c8e3aa0b565.tar.xz | |
bpf: Minor improvements for bpf_cmp.
Few minor improvements for bpf_cmp() macro:
. reduce number of args in __bpf_cmp()
. rename NOFLIP to UNLIKELY
. add a comment about 64-bit truncation in "i" constraint
. use "ri" constraint for sizeof(rhs) <= 4
. improve error message for bpf_cmp_likely()
Before:
progs/iters_task_vma.c:31:7: error: variable 'ret' is uninitialized when used here [-Werror,-Wuninitialized]
31 | if (bpf_cmp_likely(seen, <==, 1000))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../bpf/bpf_experimental.h:325:3: note: expanded from macro 'bpf_cmp_likely'
325 | ret;
| ^~~
progs/iters_task_vma.c:31:7: note: variable 'ret' is declared here
../bpf/bpf_experimental.h:310:3: note: expanded from macro 'bpf_cmp_likely'
310 | bool ret;
| ^
After:
progs/iters_task_vma.c:31:7: error: invalid operand for instruction
31 | if (bpf_cmp_likely(seen, <==, 1000))
| ^
../bpf/bpf_experimental.h:324:17: note: expanded from macro 'bpf_cmp_likely'
324 | asm volatile("r0 " #OP " invalid compare");
| ^
<inline asm>:1:5: note: instantiated into assembly here
1 | r0 <== invalid compare
| ^
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20240112220134.71209-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/testing/selftests/bpf/bpf_experimental.h')
| -rw-r--r-- | tools/testing/selftests/bpf/bpf_experimental.h | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h index f44875f8b367..0d749006d107 100644 --- a/tools/testing/selftests/bpf/bpf_experimental.h +++ b/tools/testing/selftests/bpf/bpf_experimental.h @@ -260,11 +260,11 @@ extern void bpf_throw(u64 cookie) __ksym; #define __is_signed_type(type) (((type)(-1)) < (type)1) -#define __bpf_cmp(LHS, OP, SIGN, PRED, RHS, DEFAULT) \ +#define __bpf_cmp(LHS, OP, PRED, RHS, DEFAULT) \ ({ \ __label__ l_true; \ bool ret = DEFAULT; \ - asm volatile goto("if %[lhs] " SIGN #OP " %[rhs] goto %l[l_true]" \ + asm volatile goto("if %[lhs] " OP " %[rhs] goto %l[l_true]" \ :: [lhs] "r"((short)LHS), [rhs] PRED (RHS) :: l_true); \ ret = !DEFAULT; \ l_true: \ @@ -276,7 +276,7 @@ l_true: \ * __lhs OP __rhs below will catch the mistake. * Be aware that we check only __lhs to figure out the sign of compare. */ -#define _bpf_cmp(LHS, OP, RHS, NOFLIP) \ +#define _bpf_cmp(LHS, OP, RHS, UNLIKELY) \ ({ \ typeof(LHS) __lhs = (LHS); \ typeof(RHS) __rhs = (RHS); \ @@ -285,14 +285,17 @@ l_true: \ (void)(__lhs OP __rhs); \ if (__cmp_cannot_be_signed(OP) || !__is_signed_type(typeof(__lhs))) { \ if (sizeof(__rhs) == 8) \ - ret = __bpf_cmp(__lhs, OP, "", "r", __rhs, NOFLIP); \ + /* "i" will truncate 64-bit constant into s32, \ + * so we have to use extra register via "r". \ + */ \ + ret = __bpf_cmp(__lhs, #OP, "r", __rhs, UNLIKELY); \ else \ - ret = __bpf_cmp(__lhs, OP, "", "i", __rhs, NOFLIP); \ + ret = __bpf_cmp(__lhs, #OP, "ri", __rhs, UNLIKELY); \ } else { \ if (sizeof(__rhs) == 8) \ - ret = __bpf_cmp(__lhs, OP, "s", "r", __rhs, NOFLIP); \ + ret = __bpf_cmp(__lhs, "s"#OP, "r", __rhs, UNLIKELY); \ else \ - ret = __bpf_cmp(__lhs, OP, "s", "i", __rhs, NOFLIP); \ + ret = __bpf_cmp(__lhs, "s"#OP, "ri", __rhs, UNLIKELY); \ } \ ret; \ }) @@ -304,7 +307,7 @@ l_true: \ #ifndef bpf_cmp_likely #define bpf_cmp_likely(LHS, OP, RHS) \ ({ \ - bool ret; \ + bool ret = 0; \ if (__builtin_strcmp(#OP, "==") == 0) \ ret = _bpf_cmp(LHS, !=, RHS, false); \ else if (__builtin_strcmp(#OP, "!=") == 0) \ @@ -318,7 +321,7 @@ l_true: \ else if (__builtin_strcmp(#OP, ">=") == 0) \ ret = _bpf_cmp(LHS, <, RHS, false); \ else \ - (void) "bug"; \ + asm volatile("r0 " #OP " invalid compare"); \ ret; \ }) #endif |