tools/lib/bpf/btf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
The hash_combine() could be trapped when compiled with sanitizer like "zig cc".
This patch changes parameters to __u32 to fix it.
Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
---
tools/lib/bpf/btf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 8befb8103e32..11ccb5aa4958 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -3548,7 +3548,7 @@ struct btf_dedup {
struct strset *strs_set;
};
-static long hash_combine(long h, long value)
+static __u32 hash_combine(__u32 h, __u32 value)
{
return h * 31 + value;
}
--
2.42.0On Fri, Nov 15, 2024 at 2:51 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
>
> The hash_combine() could be trapped when compiled with sanitizer like "zig cc".
> This patch changes parameters to __u32 to fix it.
Can you please elaborate? What exactly are you fixing? "Undefined"
signed integer overflow? I can consider changing long to unsigned
long, but I don't think we should downgrade from long all the way to
32-bit u32. I'd rather keep all those 64 bits for hash.
pw-bot: cr
>
> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
> tools/lib/bpf/btf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 8befb8103e32..11ccb5aa4958 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -3548,7 +3548,7 @@ struct btf_dedup {
> struct strset *strs_set;
> };
>
> -static long hash_combine(long h, long value)
> +static __u32 hash_combine(__u32 h, __u32 value)
> {
> return h * 31 + value;
> }
> --
> 2.42.0
>
>
On Fri, Nov 15, 2024 at 11:57:24AM -0800, Andrii Nakryiko wrote:
> On Fri, Nov 15, 2024 at 2:51 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
> >
> > The hash_combine() could be trapped when compiled with sanitizer like "zig cc".
> > This patch changes parameters to __u32 to fix it.
>
> Can you please elaborate? What exactly are you fixing? "Undefined"
> signed integer overflow? I can consider changing long to unsigned
> long, but I don't think we should downgrade from long all the way to
> 32-bit u32. I'd rather keep all those 64 bits for hash.
Hi, Andrii.
Actually I'm using libbpf-rs with maturin build that makes python package for
rust. It seems that it uses zig cc for cross compilation. It compiles libbpf
like this command.
CC="zig cc" make CFLAGS="-fsanitize-trap"
And hash_combine's result is like below.
0000000000063860 <hash_combine>:
63860: 55 push %rbp
63861: 48 89 e5 mov %rsp,%rbp
63864: 48 89 7d f8 mov %rdi,-0x8(%rbp)
63868: 48 89 75 f0 mov %rsi,-0x10(%rbp)
6386c: b8 1f 00 00 00 mov $0x1f,%eax
63871: 48 0f af 45 f8 imul -0x8(%rbp),%rax
63876: 48 89 45 e8 mov %rax,-0x18(%rbp)
6387a: 0f 90 c0 seto %al
6387d: 34 ff xor $0xff,%al
6387f: a8 01 test $0x1,%al
63881: 0f 85 05 00 00 00 jne 6388c <hash_combine+0x2c>
-> 63887: 67 0f b9 40 0c ud1 0xc(%eax),%eax
6388c: 48 8b 45 e8 mov -0x18(%rbp),%rax
63890: 48 03 45 f0 add -0x10(%rbp),%rax
63894: 48 89 45 e0 mov %rax,-0x20(%rbp)
63898: 0f 90 c0 seto %al
6389b: 34 ff xor $0xff,%al
6389d: a8 01 test $0x1,%al
6389f: 0f 85 04 00 00 00 jne 638a9 <hash_combine+0x49>
638a5: 67 0f b9 00 ud1 (%eax),%eax
638a9: 48 8b 45 e0 mov -0x20(%rbp),%rax
638ad: 5d pop %rbp
638ae: c3 ret
638af: 90 nop
When I'm using libbpf-rs, it receives SIGILL for ud1 instruction.
It seems more appropriate to use u64 instead of u32, doesn't it?
I'll work on it.
Thanks,
Sidong
>
> pw-bot: cr
>
> >
> > Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> > ---
> > tools/lib/bpf/btf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index 8befb8103e32..11ccb5aa4958 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
> > @@ -3548,7 +3548,7 @@ struct btf_dedup {
> > struct strset *strs_set;
> > };
> >
> > -static long hash_combine(long h, long value)
> > +static __u32 hash_combine(__u32 h, __u32 value)
> > {
> > return h * 31 + value;
> > }
> > --
> > 2.42.0
> >
> >
On 11/15/24 4:36 PM, Sidong Yang wrote:
> On Fri, Nov 15, 2024 at 11:57:24AM -0800, Andrii Nakryiko wrote:
>> On Fri, Nov 15, 2024 at 2:51 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
>>> The hash_combine() could be trapped when compiled with sanitizer like "zig cc".
>>> This patch changes parameters to __u32 to fix it.
>> Can you please elaborate? What exactly are you fixing? "Undefined"
>> signed integer overflow? I can consider changing long to unsigned
>> long, but I don't think we should downgrade from long all the way to
>> 32-bit u32. I'd rather keep all those 64 bits for hash.
> Hi, Andrii.
>
> Actually I'm using libbpf-rs with maturin build that makes python package for
> rust. It seems that it uses zig cc for cross compilation. It compiles libbpf
> like this command.
>
> CC="zig cc" make CFLAGS="-fsanitize-trap"
>
> And hash_combine's result is like below.
>
> 0000000000063860 <hash_combine>:
> 63860: 55 push %rbp
> 63861: 48 89 e5 mov %rsp,%rbp
> 63864: 48 89 7d f8 mov %rdi,-0x8(%rbp)
> 63868: 48 89 75 f0 mov %rsi,-0x10(%rbp)
> 6386c: b8 1f 00 00 00 mov $0x1f,%eax
> 63871: 48 0f af 45 f8 imul -0x8(%rbp),%rax
> 63876: 48 89 45 e8 mov %rax,-0x18(%rbp)
> 6387a: 0f 90 c0 seto %al
> 6387d: 34 ff xor $0xff,%al
> 6387f: a8 01 test $0x1,%al
> 63881: 0f 85 05 00 00 00 jne 6388c <hash_combine+0x2c>
> -> 63887: 67 0f b9 40 0c ud1 0xc(%eax),%eax
> 6388c: 48 8b 45 e8 mov -0x18(%rbp),%rax
> 63890: 48 03 45 f0 add -0x10(%rbp),%rax
> 63894: 48 89 45 e0 mov %rax,-0x20(%rbp)
> 63898: 0f 90 c0 seto %al
> 6389b: 34 ff xor $0xff,%al
> 6389d: a8 01 test $0x1,%al
> 6389f: 0f 85 04 00 00 00 jne 638a9 <hash_combine+0x49>
> 638a5: 67 0f b9 00 ud1 (%eax),%eax
> 638a9: 48 8b 45 e0 mov -0x20(%rbp),%rax
> 638ad: 5d pop %rbp
> 638ae: c3 ret
> 638af: 90 nop
>
> When I'm using libbpf-rs, it receives SIGILL for ud1 instruction.
> It seems more appropriate to use u64 instead of u32, doesn't it?
> I'll work on it.
Yes, this is due to potential integer overflow.
I tried with clang with additional flags
-fsanitize=signed-integer-overflow -fsanitize-trap=all
and disable inlining for hash_combine().
The asm code (the code is compiled with -O2)
0000000000007cb0 <hash_combine>:
7cb0: 48 6b c7 1f imulq $0x1f, %rdi, %rax
7cb4: 70 06 jo 0x7cbc <hash_combine+0xc>
7cb6: 48 01 f0 addq %rsi, %rax
7cb9: 70 06 jo 0x7cc1 <hash_combine+0x11>
7cbb: c3 retq
7cbc: 67 0f b9 40 0c ud1l 0xc(%eax), %eax
7cc1: 67 0f b9 00 ud1l (%eax), %eax
7cc5: 66 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:(%rax,%rax)
Here 'jo' means 'jump if overflow'.
So if overflow happens, 'ud1l' will execute and dump error.
Changing 'long' type to 'unsigned long' should fix the problem.
>
> Thanks,
> Sidong
>> pw-bot: cr
>>
>>> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
>>> ---
>>> tools/lib/bpf/btf.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
>>> index 8befb8103e32..11ccb5aa4958 100644
>>> --- a/tools/lib/bpf/btf.c
>>> +++ b/tools/lib/bpf/btf.c
>>> @@ -3548,7 +3548,7 @@ struct btf_dedup {
>>> struct strset *strs_set;
>>> };
>>>
>>> -static long hash_combine(long h, long value)
>>> +static __u32 hash_combine(__u32 h, __u32 value)
>>> {
>>> return h * 31 + value;
>>> }
>>> --
>>> 2.42.0
>>>
>>>
On Fri, Nov 15, 2024 at 08:39:05PM -0800, Yonghong Song wrote:
>
>
>
> On 11/15/24 4:36 PM, Sidong Yang wrote:
> > On Fri, Nov 15, 2024 at 11:57:24AM -0800, Andrii Nakryiko wrote:
> > > On Fri, Nov 15, 2024 at 2:51 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
> > > > The hash_combine() could be trapped when compiled with sanitizer like "zig cc".
> > > > This patch changes parameters to __u32 to fix it.
> > > Can you please elaborate? What exactly are you fixing? "Undefined"
> > > signed integer overflow? I can consider changing long to unsigned
> > > long, but I don't think we should downgrade from long all the way to
> > > 32-bit u32. I'd rather keep all those 64 bits for hash.
> > Hi, Andrii.
> >
> > Actually I'm using libbpf-rs with maturin build that makes python package for
> > rust. It seems that it uses zig cc for cross compilation. It compiles libbpf
> > like this command.
> >
> > CC="zig cc" make CFLAGS="-fsanitize-trap"
> >
> > And hash_combine's result is like below.
> >
> > 0000000000063860 <hash_combine>:
> > 63860: 55 push %rbp
> > 63861: 48 89 e5 mov %rsp,%rbp
> > 63864: 48 89 7d f8 mov %rdi,-0x8(%rbp)
> > 63868: 48 89 75 f0 mov %rsi,-0x10(%rbp)
> > 6386c: b8 1f 00 00 00 mov $0x1f,%eax
> > 63871: 48 0f af 45 f8 imul -0x8(%rbp),%rax
> > 63876: 48 89 45 e8 mov %rax,-0x18(%rbp)
> > 6387a: 0f 90 c0 seto %al
> > 6387d: 34 ff xor $0xff,%al
> > 6387f: a8 01 test $0x1,%al
> > 63881: 0f 85 05 00 00 00 jne 6388c <hash_combine+0x2c>
> > -> 63887: 67 0f b9 40 0c ud1 0xc(%eax),%eax
> > 6388c: 48 8b 45 e8 mov -0x18(%rbp),%rax
> > 63890: 48 03 45 f0 add -0x10(%rbp),%rax
> > 63894: 48 89 45 e0 mov %rax,-0x20(%rbp)
> > 63898: 0f 90 c0 seto %al
> > 6389b: 34 ff xor $0xff,%al
> > 6389d: a8 01 test $0x1,%al
> > 6389f: 0f 85 04 00 00 00 jne 638a9 <hash_combine+0x49>
> > 638a5: 67 0f b9 00 ud1 (%eax),%eax
> > 638a9: 48 8b 45 e0 mov -0x20(%rbp),%rax
> > 638ad: 5d pop %rbp
> > 638ae: c3 ret
> > 638af: 90 nop
> >
> > When I'm using libbpf-rs, it receives SIGILL for ud1 instruction.
> > It seems more appropriate to use u64 instead of u32, doesn't it?
> > I'll work on it.
>
> Yes, this is due to potential integer overflow.
>
> I tried with clang with additional flags
> -fsanitize=signed-integer-overflow -fsanitize-trap=all
> and disable inlining for hash_combine().
> The asm code (the code is compiled with -O2)
>
> 0000000000007cb0 <hash_combine>:
> 7cb0: 48 6b c7 1f imulq $0x1f, %rdi, %rax
> 7cb4: 70 06 jo 0x7cbc <hash_combine+0xc>
> 7cb6: 48 01 f0 addq %rsi, %rax
> 7cb9: 70 06 jo 0x7cc1 <hash_combine+0x11>
> 7cbb: c3 retq
> 7cbc: 67 0f b9 40 0c ud1l 0xc(%eax), %eax
> 7cc1: 67 0f b9 00 ud1l (%eax), %eax
> 7cc5: 66 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:(%rax,%rax)
>
> Here 'jo' means 'jump if overflow'.
> So if overflow happens, 'ud1l' will execute and dump error.
>
> Changing 'long' type to 'unsigned long' should fix the problem.
Agree, unsigned long will be good. thanks.
>
> >
> > Thanks,
> > Sidong
> > > pw-bot: cr
> > >
> > > > Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> > > > ---
> > > > tools/lib/bpf/btf.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > > > index 8befb8103e32..11ccb5aa4958 100644
> > > > --- a/tools/lib/bpf/btf.c
> > > > +++ b/tools/lib/bpf/btf.c
> > > > @@ -3548,7 +3548,7 @@ struct btf_dedup {
> > > > struct strset *strs_set;
> > > > };
> > > >
> > > > -static long hash_combine(long h, long value)
> > > > +static __u32 hash_combine(__u32 h, __u32 value)
> > > > {
> > > > return h * 31 + value;
> > > > }
> > > > --
> > > > 2.42.0
> > > >
> > > >
>
© 2016 - 2026 Red Hat, Inc.