kbuild: skip module BTF generation for out-of-tree external modules #394
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Master branch: 91b2db2 |
In some modes of operation, Kbuild allows to build modules without having
vmlinux image around. In such case, generation of module BTF is impossible.
This patch changes the behavior to emit a warning about impossibility of
generating kernel module BTF, instead of breaking the build. This is especially
important for out-of-tree external module builds.
In vmlinux-less mode:
$ make clean
$ make modules_prepare
$ touch drivers/acpi/button.c
$ make M=drivers/acpi
...
CC [M] drivers/acpi/button.o
MODPOST drivers/acpi/Module.symvers
LD [M] drivers/acpi/button.ko
BTF [M] drivers/acpi/button.ko
Skipping BTF generation for drivers/acpi/button.ko due to unavailability of vmlinux
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
... empty ...
Now with normal build:
$ make all
...
LD [M] drivers/acpi/button.ko
BTF [M] drivers/acpi/button.ko
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
[60] .BTF PROGBITS 0000000000000000 00029310
000000000000ab3f 0000000000000000 0 0 1
Reported-by: Bruce Allan <[email protected]>
Fixes: 5f9ae91 ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it")
Cc: Jessica Yu <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Given .BTF section is not allocatable, it will get trimmed after module is loaded. BPF system handles that properly by creating an independent copy of data. But prevent any accidental misused by resetting the pointer to BTF data. Suggested-by: Jessica Yu <[email protected]> Fixes: 36e6844 ("bpf: Load and verify kernel module BTFs") Cc: Greg Kroah-Hartman <[email protected]> Acked-by: Jessica Yu <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]>
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Master branch: 1c26ac6 |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=388837 irrelevant now. Closing PR. |
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
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Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 14, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
kernel-patches-daemon-bpf bot
pushed a commit
that referenced
this pull request
Feb 15, 2024
Verifier log avoids printing the same source code line multiple times
when a consecutive block of BPF assembly instructions are covered by the
same original (C) source code line. This greatly improves verifier log
legibility.
Unfortunately, this check is imperfect and in production applications it
quite often happens that verifier log will have multiple duplicated
source lines emitted, for no apparently good reason. E.g., this is
excerpt from a real-world BPF application (with register states omitted
for clarity):
BEFORE
======
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
As can be seen, line 394 is emitted thrice, 396 is emitted twice, and
line 400 is duplicated as well. Note that there are no intermingling
other lines of source code in between these duplicates, so the issue is
not compiler reordering assembly instruction such that multiple original
source code lines are in effect.
It becomes more obvious what's going on if we look at *full* original line info
information (using btfdump for this, [0]):
#2764: line: insn #5363 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2765: line: insn #5373 --> 394:21 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2766: line: insn #5375 --> 394:47 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2767: line: insn #5377 --> 394:3 @ ./././strobemeta_probe.bpf.c
for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
#2768: line: insn #5378 --> 414:10 @ ./././strobemeta_probe.bpf.c
return off;
We can see that there are four line info records covering
instructions #5363 through #5377 (instruction indices are shifted due to
subprog instruction being appended to main program), all of them are
pointing to the same C source code line #394. But each of them points to
a different part of that line, which is denoted by differing column
numbers (3, 21, 47, 3).
But verifier log doesn't distinguish between parts of the same source code line
and doesn't emit this column number information, so for end user it's just a
repetitive visual noise. So let's improve the detection of repeated source code
line and avoid this.
With the changes in this patch, we get this output for the same piece of BPF
program log:
AFTER
=====
; for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) { @ strobemeta_probe.bpf.c:394
5369: (07) r8 += 2 ;
5370: (07) r7 += 16 ;
5371: (07) r9 += 1 ;
5372: (79) r4 = *(u64 *)(r10 -32) ;
5373: (55) if r9 != 0xf goto pc+2
; if (i >= map->cnt) @ strobemeta_probe.bpf.c:396
5376: (79) r1 = *(u64 *)(r10 -40) ;
5377: (79) r1 = *(u64 *)(r1 +8) ;
5378: (dd) if r1 s<= r9 goto pc-5 ;
; descr->key_lens[i] = 0; @ strobemeta_probe.bpf.c:398
5379: (b4) w1 = 0 ;
5380: (6b) *(u16 *)(r8 -30) = r1 ;
; task, data, off, STROBE_MAX_STR_LEN, map->entries[i].key); @ strobemeta_probe.bpf.c:400
5381: (79) r3 = *(u64 *)(r7 -8) ;
5382: (7b) *(u64 *)(r10 -24) = r6 ;
5383: (bc) w6 = w6 ;
; barrier_var(payload_off); @ strobemeta_probe.bpf.c:280
5384: (bf) r2 = r6 ;
5385: (bf) r1 = r4 ;
All the duplication is gone and the log is cleaner and less distracting.
[0] https://github.com/anakryiko/btfdump
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
eddyz87
added a commit
to eddyz87/bpf
that referenced
this pull request
Jul 30, 2025
Failing tests: - kernel-patches#110 fexit_bpf2bpf:FAIL - kernel-patches#124 for_each:FAIL - kernel-patches#144 iters:FAIL - kernel-patches#148 kfree_skb:FAIL - kernel-patches#161 l4lb_all:FAIL - kernel-patches#193 map_kptr:FAIL - kernel-patches#23 bpf_loop:FAIL - kernel-patches#260 pkt_access:FAIL - kernel-patches#269 prog_run_opts:FAIL - kernel-patches#280 rbtree_success:FAIL - kernel-patches#356 res_spin_lock_failure:FAIL - kernel-patches#364 setget_sockopt:FAIL - kernel-patches#381 sock_fields:FAIL - kernel-patches#394 spin_lock:FAIL - kernel-patches#395 spin_lock_success:FAIL - kernel-patches#444 test_bpffs:FAIL - kernel-patches#453 test_profiler:FAIL - kernel-patches#479 usdt:FAIL - kernel-patches#488 verifier_bits_iter:FAIL - kernel-patches#597 verif_scale_pyperf600:FAIL - kernel-patches#598 verif_scale_pyperf600_bpf_loop:FAIL - kernel-patches#599 verif_scale_pyperf600_iter:FAIL - kernel-patches#608 verif_scale_strobemeta_subprogs:FAIL - kernel-patches#622 xdp_attach:FAIL - kernel-patches#637 xdp_noinline:FAIL - kernel-patches#639 xdp_synproxy:FAIL - kernel-patches#72 cls_redirect:FAIL - kernel-patches#88 crypto_sanity:FAIL - kernel-patches#97 dynptr:FAIL Signed-off-by: Eduard Zingerman <[email protected]>
eddyz87
added a commit
to eddyz87/bpf
that referenced
this pull request
Jul 30, 2025
Failing tests: - kernel-patches#110 fexit_bpf2bpf:FAIL - kernel-patches#124 for_each:FAIL - kernel-patches#144 iters:FAIL - kernel-patches#148 kfree_skb:FAIL - kernel-patches#161 l4lb_all:FAIL - kernel-patches#193 map_kptr:FAIL - kernel-patches#23 bpf_loop:FAIL - kernel-patches#260 pkt_access:FAIL - kernel-patches#269 prog_run_opts:FAIL - kernel-patches#280 rbtree_success:FAIL - kernel-patches#356 res_spin_lock_failure:FAIL - kernel-patches#364 setget_sockopt:FAIL - kernel-patches#381 sock_fields:FAIL - kernel-patches#394 spin_lock:FAIL - kernel-patches#395 spin_lock_success:FAIL - kernel-patches#444 test_bpffs:FAIL - kernel-patches#453 test_profiler:FAIL - kernel-patches#479 usdt:FAIL - kernel-patches#488 verifier_bits_iter:FAIL - kernel-patches#597 verif_scale_pyperf600:FAIL - kernel-patches#598 verif_scale_pyperf600_bpf_loop:FAIL - kernel-patches#599 verif_scale_pyperf600_iter:FAIL - kernel-patches#608 verif_scale_strobemeta_subprogs:FAIL - kernel-patches#622 xdp_attach:FAIL - kernel-patches#637 xdp_noinline:FAIL - kernel-patches#639 xdp_synproxy:FAIL - kernel-patches#72 cls_redirect:FAIL - kernel-patches#88 crypto_sanity:FAIL - kernel-patches#97 dynptr:FAIL Signed-off-by: Eduard Zingerman <[email protected]>
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Pull request for series with
subject: kbuild: skip module BTF generation for out-of-tree external modules
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=388837