releases/5.4.160/selftests-bpf-fix-also-no-alu32-strobemeta-selftest.patch

From a20eac0af02810669e187cb623bc904908c423af Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@kernel.org>
Date: Mon, 1 Nov 2021 16:01:18 -0700
Subject: selftests/bpf: Fix also no-alu32 strobemeta selftest

From: Andrii Nakryiko <andrii@kernel.org>

commit a20eac0af02810669e187cb623bc904908c423af upstream.

Previous fix aded bpf_clamp_umax() helper use to re-validate boundaries.
While that works correctly, it introduces more branches, which blows up
past 1 million instructions in no-alu32 variant of strobemeta selftests.

Switching len variable from u32 to u64 also fixes the issue and reduces
the number of validated instructions, so use that instead. Fix this
patch and bpf_clamp_umax() removed, both alu32 and no-alu32 selftests
pass.

Fixes: 0133c20480b1 ("selftests/bpf: Fix strobemeta selftest regression")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211101230118.1273019-1-andrii@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/testing/selftests/bpf/progs/strobemeta.h |   15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

--- a/tools/testing/selftests/bpf/progs/strobemeta.h
+++ b/tools/testing/selftests/bpf/progs/strobemeta.h
@@ -10,14 +10,6 @@
 #include <linux/types.h>
 #include "bpf_helpers.h"
 
-#define bpf_clamp_umax(VAR, UMAX)					\
-	asm volatile (							\
-		"if %0 <= %[max] goto +1\n"				\
-		"%0 = %[max]\n"						\
-		: "+r"(VAR)						\
-		: [max]"i"(UMAX)					\
-	)
-
 typedef uint32_t pid_t;
 struct task_struct {};
 
@@ -357,7 +349,7 @@ static __always_inline uint64_t read_str
 					     void *payload)
 {
 	void *location;
-	uint32_t len;
+	uint64_t len;
 
 	data->str_lens[idx] = 0;
 	location = calc_location(&cfg->str_locs[idx], tls_base);
@@ -389,7 +381,7 @@ static __always_inline void *read_map_va
 	struct strobe_map_descr* descr = &data->map_descrs[idx];
 	struct strobe_map_raw map;
 	void *location;
-	uint32_t len;
+	uint64_t len;
 	int i;
 
 	descr->tag_len = 0; /* presume no tag is set */
@@ -412,7 +404,6 @@ static __always_inline void *read_map_va
 
 	len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN, map.tag);
 	if (len <= STROBE_MAX_STR_LEN) {
-		bpf_clamp_umax(len, STROBE_MAX_STR_LEN);
 		descr->tag_len = len;
 		payload += len;
 	}
@@ -430,7 +421,6 @@ static __always_inline void *read_map_va
 		len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN,
 					 map.entries[i].key);
 		if (len <= STROBE_MAX_STR_LEN) {
-			bpf_clamp_umax(len, STROBE_MAX_STR_LEN);
 			descr->key_lens[i] = len;
 			payload += len;
 		}
@@ -438,7 +428,6 @@ static __always_inline void *read_map_va
 		len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN,
 					 map.entries[i].val);
 		if (len <= STROBE_MAX_STR_LEN) {
-			bpf_clamp_umax(len, STROBE_MAX_STR_LEN);
 			descr->val_lens[i] = len;
 			payload += len;
 		}