* [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures
@ 2020-07-17 16:53 Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree Ilya Leoshkevich
` (5 more replies)
0 siblings, 6 replies; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich
This patch series fixes three regressions caused by 4e9b4a6883dd
("s390/bpf: Use relative long branches") reported by Seth Forshee
(patches 2-4) and adds two minor related improvements (patches 1
and 5).
Ilya Leoshkevich (5):
selftests: bpf: test_kmod.sh: fix running out of srctree
s390/bpf: fix sign extension in branch_ku
s390/bpf: use brcl for jumping to exit_ip if necessary
s390/bpf: tolerate not converging code shrinking
s390/bpf: use bpf_skip() in bpf_jit_prologue()
arch/s390/net/bpf_jit_comp.c | 63 +++++++++++++++---------
tools/testing/selftests/bpf/test_kmod.sh | 12 +++--
2 files changed, 50 insertions(+), 25 deletions(-)
--
2.25.4
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
@ 2020-07-17 16:53 ` Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 2/5] s390/bpf: fix sign extension in branch_ku Ilya Leoshkevich
` (4 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich
When running out of srctree, relative path to lib/test_bpf.ko is
different than when running in srctree. Check $building_out_of_srctree
environment variable and use a different relative path if needed.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
tools/testing/selftests/bpf/test_kmod.sh | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_kmod.sh b/tools/testing/selftests/bpf/test_kmod.sh
index 9df0d2ac45f8..4f6444bcd53f 100755
--- a/tools/testing/selftests/bpf/test_kmod.sh
+++ b/tools/testing/selftests/bpf/test_kmod.sh
@@ -10,7 +10,13 @@ if [ "$(id -u)" != "0" ]; then
exit $ksft_skip
fi
-SRC_TREE=../../../../
+if [ "$building_out_of_srctree" ]; then
+ # We are in linux-build/kselftest/bpf
+ OUTPUT=../../
+else
+ # We are in linux/tools/testing/selftests/bpf
+ OUTPUT=../../../../
+fi
test_run()
{
@@ -19,8 +25,8 @@ test_run()
echo "[ JIT enabled:$1 hardened:$2 ]"
dmesg -C
- if [ -f ${SRC_TREE}/lib/test_bpf.ko ]; then
- insmod ${SRC_TREE}/lib/test_bpf.ko 2> /dev/null
+ if [ -f ${OUTPUT}/lib/test_bpf.ko ]; then
+ insmod ${OUTPUT}/lib/test_bpf.ko 2> /dev/null
if [ $? -ne 0 ]; then
rc=1
fi
--
2.25.4
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 2/5] s390/bpf: fix sign extension in branch_ku
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree Ilya Leoshkevich
@ 2020-07-17 16:53 ` Ilya Leoshkevich
2020-07-17 22:23 ` Seth Forshee
2020-07-17 16:53 ` [PATCH 3/5] s390/bpf: use brcl for jumping to exit_ip if necessary Ilya Leoshkevich
` (3 subsequent siblings)
5 siblings, 1 reply; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich, Seth Forshee
Both signed and unsigned variants of BPF_JMP | BPF_K require
sign-extending the immediate. JIT emits cgfi for the signed case,
which is correct, and clgfi for the unsigned case, which is not
correct: clgfi zero-extends the immediate.
s390 does not provide an instruction that does sign-extension and
unsigned comparison at the same time. Therefore, fix by first loading
the sign-extended immediate into work register REG_1 and proceeding
as if it's BPF_X.
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
Reported-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/net/bpf_jit_comp.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 8fe7bdfc8d15..67608f6092f8 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1507,21 +1507,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
}
break;
branch_ku:
- is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
- /* clfi or clgfi %dst,imm */
- EMIT6_IMM(is_jmp32 ? 0xc20f0000 : 0xc20e0000,
- dst_reg, imm);
- if (!is_first_pass(jit) &&
- can_use_rel(jit, addrs[i + off + 1])) {
- /* brc mask,off */
- EMIT4_PCREL_RIC(0xa7040000,
- mask >> 12, addrs[i + off + 1]);
- } else {
- /* brcl mask,off */
- EMIT6_PCREL_RILC(0xc0040000,
- mask >> 12, addrs[i + off + 1]);
- }
- break;
+ /* lgfi %w1,imm (load sign extend imm) */
+ src_reg = REG_1;
+ EMIT6_IMM(0xc0010000, src_reg, imm);
+ goto branch_xu;
branch_xs:
is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
if (!is_first_pass(jit) &&
--
2.25.4
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 3/5] s390/bpf: use brcl for jumping to exit_ip if necessary
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 2/5] s390/bpf: fix sign extension in branch_ku Ilya Leoshkevich
@ 2020-07-17 16:53 ` Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 4/5] s390/bpf: tolerate not converging code shrinking Ilya Leoshkevich
` (2 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich
"BPF_MAXINSNS: Maximum possible literals" test causes panic with
bpf_jit_harden = 2. The reason is that BPF_JMP | BPF_EXIT is always
emitted as brc, however, after removal of JITed image size
limitations, brcl might be required.
Fix by using brcl when necessary.
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/net/bpf_jit_comp.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 67608f6092f8..625ebe32b2d1 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1358,8 +1358,12 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
last = (i == fp->len - 1) ? 1 : 0;
if (last)
break;
- /* j <exit> */
- EMIT4_PCREL(0xa7f40000, jit->exit_ip - jit->prg);
+ if (!is_first_pass(jit) && can_use_rel(jit, jit->exit_ip))
+ /* brc 0xf, <exit> */
+ EMIT4_PCREL_RIC(0xa7040000, 0xf, jit->exit_ip);
+ else
+ /* brcl 0xf, <exit> */
+ EMIT6_PCREL_RILC(0xc0040000, 0xf, jit->exit_ip);
break;
/*
* Branch relative (number of skipped instructions) to offset on
--
2.25.4
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 4/5] s390/bpf: tolerate not converging code shrinking
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
` (2 preceding siblings ...)
2020-07-17 16:53 ` [PATCH 3/5] s390/bpf: use brcl for jumping to exit_ip if necessary Ilya Leoshkevich
@ 2020-07-17 16:53 ` Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 5/5] s390/bpf: use bpf_skip() in bpf_jit_prologue() Ilya Leoshkevich
2020-07-21 18:17 ` [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Alexei Starovoitov
5 siblings, 0 replies; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich
"BPF_MAXINSNS: Maximum possible literals" unnecessarily falls back to
the interpreter because of failing sanity check in bpf_set_addr. The
problem is that there are a lot of branches that can be shrunk, and
doing so opens up the possibility to shrink even more. This process
does not converge after 3 passes, causing code offsets to change during
the codegen pass, which must never happen.
Fix by inserting nops during codegen pass in order to preserve code
offets.
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/net/bpf_jit_comp.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 625ebe32b2d1..e68854ab27ae 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -490,6 +490,24 @@ static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth)
} while (re <= last);
}
+static void bpf_skip(struct bpf_jit *jit, int size)
+{
+ if (size >= 6 && !is_valid_rel(size)) {
+ /* brcl 0xf,size */
+ EMIT6_PCREL_RIL(0xc0f4000000, size);
+ size -= 6;
+ } else if (size >= 4 && is_valid_rel(size)) {
+ /* brc 0xf,size */
+ EMIT4_PCREL(0xa7f40000, size);
+ size -= 4;
+ }
+ while (size >= 2) {
+ /* bcr 0,%0 */
+ _EMIT2(0x0700);
+ size -= 2;
+ }
+}
+
/*
* Emit function prologue
*
@@ -1610,7 +1628,14 @@ static bool bpf_is_new_addr_sane(struct bpf_jit *jit, int i)
*/
static int bpf_set_addr(struct bpf_jit *jit, int i)
{
- if (!bpf_is_new_addr_sane(jit, i))
+ int delta;
+
+ if (is_codegen_pass(jit)) {
+ delta = jit->prg - jit->addrs[i];
+ if (delta < 0)
+ bpf_skip(jit, -delta);
+ }
+ if (WARN_ON_ONCE(!bpf_is_new_addr_sane(jit, i)))
return -1;
jit->addrs[i] = jit->prg;
return 0;
--
2.25.4
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 5/5] s390/bpf: use bpf_skip() in bpf_jit_prologue()
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
` (3 preceding siblings ...)
2020-07-17 16:53 ` [PATCH 4/5] s390/bpf: tolerate not converging code shrinking Ilya Leoshkevich
@ 2020-07-17 16:53 ` Ilya Leoshkevich
2020-07-21 18:17 ` [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Alexei Starovoitov
5 siblings, 0 replies; 8+ messages in thread
From: Ilya Leoshkevich @ 2020-07-17 16:53 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann
Cc: bpf, Heiko Carstens, Vasily Gorbik, Ilya Leoshkevich
Now that we have bpf_skip() for emitting nops, use it in
bpf_jit_prologue() in order to reduce code duplication.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
arch/s390/net/bpf_jit_comp.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index e68854ab27ae..be4b8532dd3c 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -520,10 +520,11 @@ static void bpf_jit_prologue(struct bpf_jit *jit, u32 stack_depth)
/* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */
_EMIT6(0xd703f000 | STK_OFF_TCCNT, 0xf000 | STK_OFF_TCCNT);
} else {
- /* j tail_call_start: NOP if no tail calls are used */
- EMIT4_PCREL(0xa7f40000, 6);
- /* bcr 0,%0 */
- EMIT2(0x0700, 0, REG_0);
+ /*
+ * There are no tail calls. Insert nops in order to have
+ * tail_call_start at a predictable offset.
+ */
+ bpf_skip(jit, 6);
}
/* Tail calls have to skip above initialization */
jit->tail_call_start = jit->prg;
--
2.25.4
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH 2/5] s390/bpf: fix sign extension in branch_ku
2020-07-17 16:53 ` [PATCH 2/5] s390/bpf: fix sign extension in branch_ku Ilya Leoshkevich
@ 2020-07-17 22:23 ` Seth Forshee
0 siblings, 0 replies; 8+ messages in thread
From: Seth Forshee @ 2020-07-17 22:23 UTC (permalink / raw)
To: Ilya Leoshkevich
Cc: Alexei Starovoitov, Daniel Borkmann, bpf, Heiko Carstens, Vasily Gorbik
On Fri, Jul 17, 2020 at 06:53:23PM +0200, Ilya Leoshkevich wrote:
> Both signed and unsigned variants of BPF_JMP | BPF_K require
> sign-extending the immediate. JIT emits cgfi for the signed case,
> which is correct, and clgfi for the unsigned case, which is not
> correct: clgfi zero-extends the immediate.
>
> s390 does not provide an instruction that does sign-extension and
> unsigned comparison at the same time. Therefore, fix by first loading
> the sign-extended immediate into work register REG_1 and proceeding
> as if it's BPF_X.
>
> Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
> Reported-by: Seth Forshee <seth.forshee@canonical.com>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
This fixes the failing tests I was seeing. Thanks!
Tested-by: Seth Forshee <seth.forshee@canonical.com>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
` (4 preceding siblings ...)
2020-07-17 16:53 ` [PATCH 5/5] s390/bpf: use bpf_skip() in bpf_jit_prologue() Ilya Leoshkevich
@ 2020-07-21 18:17 ` Alexei Starovoitov
5 siblings, 0 replies; 8+ messages in thread
From: Alexei Starovoitov @ 2020-07-21 18:17 UTC (permalink / raw)
To: Ilya Leoshkevich
Cc: Alexei Starovoitov, Daniel Borkmann, bpf, Heiko Carstens, Vasily Gorbik
On Fri, Jul 17, 2020 at 9:53 AM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> This patch series fixes three regressions caused by 4e9b4a6883dd
> ("s390/bpf: Use relative long branches") reported by Seth Forshee
> (patches 2-4) and adds two minor related improvements (patches 1
> and 5).
Applied. Thanks
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-07-21 18:17 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 2/5] s390/bpf: fix sign extension in branch_ku Ilya Leoshkevich
2020-07-17 22:23 ` Seth Forshee
2020-07-17 16:53 ` [PATCH 3/5] s390/bpf: use brcl for jumping to exit_ip if necessary Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 4/5] s390/bpf: tolerate not converging code shrinking Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 5/5] s390/bpf: use bpf_skip() in bpf_jit_prologue() Ilya Leoshkevich
2020-07-21 18:17 ` [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Alexei Starovoitov
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