Message ID | 20230426055030.3743074-1-yhs@fb.com (mailing list archive) |
---|---|
State | Not Applicable |
Delegated to: | BPF |
Headers | show |
Series | [dwarves] btf_encoder: Fix a dwarf type DW_ATE_unsigned_1024 to btf encoding issue | expand |
On Tue, Apr 25, 2023 at 10:50 PM Yonghong Song <yhs@fb.com> wrote: > > Nick Desaulniers reported an issue ([1]) where an 128-byte sized type > (DW_ATE_unsigned_1024) cannot be encoded into BTF with failure message > likes below: > $ pahole -J reduced.o > [2] INT DW_ATE_unsigned_1024 Error emitting BTF type > Encountered error while encoding BTF. > See [1] for how to reproduce the issue. > > The failure is due to currently BTF int type only supports upto 16 > bytes (__int128) and in this case the dwarf int type is 128-byte. > > The DW_ATE_unsigned_1024 is not a normal type for variable/func > declaration etc. It is used in DW_AT_location. There are two > ways to resolve this issue. > (1). If btf encoding is expected, remove all dwarf int types > where btf encoding will failure, e.g., non-power-of-2 > bytes, or greater than 16 bytes. > (2). do a sanitization in btf_encoder ([2]). > > This patch uses method (2) since it is a simple fix in btf_encoder. > I checked my local built vmlinux with latest > bpf-next. There is only one instance of DW_ATE_unsigned_24 (used in > DW_AT_location) so I expect irregular int types should be very rare. > > [1] https://github.com/libbpf/libbpf/pull/680 > [2] commit 7d8e829f636f ("btf_encoder: Sanitize non-regular int base type") > > Signed-off-by: Yonghong Song <yhs@fb.com> Thanks, this fixed the above reported error for me. My report is just forwarded from Satya. Reported-by: Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> I don't know if that change has other implications for unusual byte sizes. We might need to consider at some point waiting to validate DW_TAG_base_type until we know that they're not used outside of DW_AT_location expressions. > --- > btf_encoder.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/btf_encoder.c b/btf_encoder.c > index 65f6e71..1aa0ad0 100644 > --- a/btf_encoder.c > +++ b/btf_encoder.c > @@ -394,7 +394,7 @@ static int32_t btf_encoder__add_base_type(struct btf_encoder *encoder, const str > * these non-regular int types to avoid libbpf/kernel complaints. > */ > byte_sz = BITS_ROUNDUP_BYTES(bt->bit_size); > - if (!byte_sz || (byte_sz & (byte_sz - 1))) { > + if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 16) { > name = "__SANITIZED_FAKE_INT__"; > byte_sz = 4; > } > -- > 2.34.1 >
On 4/26/23 11:09 AM, Nick Desaulniers wrote: > On Tue, Apr 25, 2023 at 10:50 PM Yonghong Song <yhs@fb.com> wrote: >> >> Nick Desaulniers reported an issue ([1]) where an 128-byte sized type >> (DW_ATE_unsigned_1024) cannot be encoded into BTF with failure message >> likes below: >> $ pahole -J reduced.o >> [2] INT DW_ATE_unsigned_1024 Error emitting BTF type >> Encountered error while encoding BTF. >> See [1] for how to reproduce the issue. >> >> The failure is due to currently BTF int type only supports upto 16 >> bytes (__int128) and in this case the dwarf int type is 128-byte. >> >> The DW_ATE_unsigned_1024 is not a normal type for variable/func >> declaration etc. It is used in DW_AT_location. There are two >> ways to resolve this issue. >> (1). If btf encoding is expected, remove all dwarf int types >> where btf encoding will failure, e.g., non-power-of-2 >> bytes, or greater than 16 bytes. >> (2). do a sanitization in btf_encoder ([2]). >> >> This patch uses method (2) since it is a simple fix in btf_encoder. >> I checked my local built vmlinux with latest >> bpf-next. There is only one instance of DW_ATE_unsigned_24 (used in >> DW_AT_location) so I expect irregular int types should be very rare. >> >> [1] https://github.com/libbpf/libbpf/pull/680 >> [2] commit 7d8e829f636f ("btf_encoder: Sanitize non-regular int base type") >> >> Signed-off-by: Yonghong Song <yhs@fb.com> > > Thanks, this fixed the above reported error for me. My report is just > forwarded from Satya. > > Reported-by: Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com> > Tested-by: Nick Desaulniers <ndesaulniers@google.com> > > I don't know if that change has other implications for unusual byte sizes. > > We might need to consider at some point waiting to validate > DW_TAG_base_type until we know that they're not used outside of > DW_AT_location expressions. David Blaikie confirmed that indeed special types like DW_ATE_unsigned_1024 is indeed generated for DW_AT_location. See https://github.com/libbpf/libbpf/pull/680 for details. > >> --- >> btf_encoder.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/btf_encoder.c b/btf_encoder.c >> index 65f6e71..1aa0ad0 100644 >> --- a/btf_encoder.c >> +++ b/btf_encoder.c >> @@ -394,7 +394,7 @@ static int32_t btf_encoder__add_base_type(struct btf_encoder *encoder, const str >> * these non-regular int types to avoid libbpf/kernel complaints. >> */ >> byte_sz = BITS_ROUNDUP_BYTES(bt->bit_size); >> - if (!byte_sz || (byte_sz & (byte_sz - 1))) { >> + if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 16) { >> name = "__SANITIZED_FAKE_INT__"; >> byte_sz = 4; >> } >> -- >> 2.34.1 >> > >
diff --git a/btf_encoder.c b/btf_encoder.c index 65f6e71..1aa0ad0 100644 --- a/btf_encoder.c +++ b/btf_encoder.c @@ -394,7 +394,7 @@ static int32_t btf_encoder__add_base_type(struct btf_encoder *encoder, const str * these non-regular int types to avoid libbpf/kernel complaints. */ byte_sz = BITS_ROUNDUP_BYTES(bt->bit_size); - if (!byte_sz || (byte_sz & (byte_sz - 1))) { + if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 16) { name = "__SANITIZED_FAKE_INT__"; byte_sz = 4; }
Nick Desaulniers reported an issue ([1]) where an 128-byte sized type (DW_ATE_unsigned_1024) cannot be encoded into BTF with failure message likes below: $ pahole -J reduced.o [2] INT DW_ATE_unsigned_1024 Error emitting BTF type Encountered error while encoding BTF. See [1] for how to reproduce the issue. The failure is due to currently BTF int type only supports upto 16 bytes (__int128) and in this case the dwarf int type is 128-byte. The DW_ATE_unsigned_1024 is not a normal type for variable/func declaration etc. It is used in DW_AT_location. There are two ways to resolve this issue. (1). If btf encoding is expected, remove all dwarf int types where btf encoding will failure, e.g., non-power-of-2 bytes, or greater than 16 bytes. (2). do a sanitization in btf_encoder ([2]). This patch uses method (2) since it is a simple fix in btf_encoder. I checked my local built vmlinux with latest bpf-next. There is only one instance of DW_ATE_unsigned_24 (used in DW_AT_location) so I expect irregular int types should be very rare. [1] https://github.com/libbpf/libbpf/pull/680 [2] commit 7d8e829f636f ("btf_encoder: Sanitize non-regular int base type") Signed-off-by: Yonghong Song <yhs@fb.com> --- btf_encoder.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)