| Message ID | 20210125130625.2030186-1-gprocida@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | BTF ELF writing changes | expand |
On Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida wrote: > Hi. > > This follows on from my change to improve the error handling around > llvm-objcopy in libbtf.c. > > Note on recipients: Please let me know if I should adjust To or CC. > > Note on style: I've generally placed declarations as allowed by C99, > closest to point of use. Let me know if you'd prefer otherwise. > > 1. Improve ELF error reporting > > 2. Add .BTF section using libelf > > This shows the minimal amount of code needed to drive libelf. However, > it leaves layout up to libelf, which is almost certainly not wanted. > > As an unexpcted side-effect, vmlinux is larger than before. It seems > llvm-objcopy likes to trim down .strtab. > > 3. Manually lay out updated ELF sections > > This does full layout of new and updated ELF sections. If the update > ELF sections were not the last ones in the file by offset, then it can > leave gaps between sections. > > 4. Align .BTF section to 8 bytes > > This was my original aim. > > Regards. > > Giuliano Procida (4): > btf_encoder: Improve ELF error reporting > btf_encoder: Add .BTF section using libelf > btf_encoder: Manually lay out updated ELF sections > btf_encoder: Align .BTF section to 8 bytes hi, I can't apply this on dwarves git master, which commit is it based on? thanks, jirka > > libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 175 insertions(+), 47 deletions(-) > > -- > 2.30.0.280.ga3ce27912f-goog >
Hi. On Tue, 26 Jan 2021 at 19:56, Jiri Olsa <jolsa@redhat.com> wrote: > > On Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida wrote: > > Hi. > > > > This follows on from my change to improve the error handling around > > llvm-objcopy in libbtf.c. > > > > Note on recipients: Please let me know if I should adjust To or CC. > > > > Note on style: I've generally placed declarations as allowed by C99, > > closest to point of use. Let me know if you'd prefer otherwise. > > > > 1. Improve ELF error reporting > > > > 2. Add .BTF section using libelf > > > > This shows the minimal amount of code needed to drive libelf. However, > > it leaves layout up to libelf, which is almost certainly not wanted. > > > > As an unexpcted side-effect, vmlinux is larger than before. It seems > > llvm-objcopy likes to trim down .strtab. > > > > 3. Manually lay out updated ELF sections > > > > This does full layout of new and updated ELF sections. If the update > > ELF sections were not the last ones in the file by offset, then it can > > leave gaps between sections. > > > > 4. Align .BTF section to 8 bytes > > > > This was my original aim. > > > > Regards. > > > > Giuliano Procida (4): > > btf_encoder: Improve ELF error reporting > > btf_encoder: Add .BTF section using libelf > > btf_encoder: Manually lay out updated ELF sections > > btf_encoder: Align .BTF section to 8 bytes > > hi, > I can't apply this on dwarves git master, which commit is it based on? > It's based on: https://www.spinics.net/lists/dwarves/msg00775.html (0/3) https://www.spinics.net/lists/dwarves/msg00774.html (1/3, unrelated fix) https://www.spinics.net/lists/dwarves/msg00773.html (2/3, this is the one you'll need for a clean git am; obsoleted by this new series) (3/3 was abandoned) Arnaldo did say the two commits were applied... but perhaps they haven't been pushed to public master yet. > thanks, > jirka > You're welcome. Giuliano. > > > > libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------ > > 1 file changed, 175 insertions(+), 47 deletions(-) > > > > -- > > 2.30.0.280.ga3ce27912f-goog > > >
Em Wed, Jan 27, 2021 at 01:10:40AM +0000, Giuliano Procida escreveu: > Hi. > > On Tue, 26 Jan 2021 at 19:56, Jiri Olsa <jolsa@redhat.com> wrote: > > > > On Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida wrote: > > > Hi. > > > > > > This follows on from my change to improve the error handling around > > > llvm-objcopy in libbtf.c. > > > > > > Note on recipients: Please let me know if I should adjust To or CC. > > > > > > Note on style: I've generally placed declarations as allowed by C99, > > > closest to point of use. Let me know if you'd prefer otherwise. > > > > > > 1. Improve ELF error reporting > > > > > > 2. Add .BTF section using libelf > > > > > > This shows the minimal amount of code needed to drive libelf. However, > > > it leaves layout up to libelf, which is almost certainly not wanted. > > > > > > As an unexpcted side-effect, vmlinux is larger than before. It seems > > > llvm-objcopy likes to trim down .strtab. > > > > > > 3. Manually lay out updated ELF sections > > > > > > This does full layout of new and updated ELF sections. If the update > > > ELF sections were not the last ones in the file by offset, then it can > > > leave gaps between sections. > > > > > > 4. Align .BTF section to 8 bytes > > > > > > This was my original aim. > > > > > > Regards. > > > > > > Giuliano Procida (4): > > > btf_encoder: Improve ELF error reporting > > > btf_encoder: Add .BTF section using libelf > > > btf_encoder: Manually lay out updated ELF sections > > > btf_encoder: Align .BTF section to 8 bytes > > > > hi, > > I can't apply this on dwarves git master, which commit is it based on? > > > > It's based on: > https://www.spinics.net/lists/dwarves/msg00775.html (0/3) > https://www.spinics.net/lists/dwarves/msg00774.html (1/3, unrelated fix) > https://www.spinics.net/lists/dwarves/msg00773.html (2/3, this is the > one you'll need for a clean git am; obsoleted by this new series) > (3/3 was abandoned) > > Arnaldo did say the two commits were applied... but perhaps they > haven't been pushed to public master yet. I pushed what I have now, please check if anything is missing. I'm now working on DWARF4's DW_AT_data_bit_offset, that gcc uses when dwarf-5 is asked for, I should have something usable tomorrow and hopefully this will be the last stuff to get into 1.20. dd thanks, - Arnaldo > > thanks, > > jirka > > > > You're welcome. > Giuliano. > > > > > > > libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------ > > > 1 file changed, 175 insertions(+), 47 deletions(-) > > > > > > -- > > > 2.30.0.280.ga3ce27912f-goog > > > > >
Em Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida escreveu: > Hi. > > This follows on from my change to improve the error handling around > llvm-objcopy in libbtf.c. > > Note on recipients: Please let me know if I should adjust To or CC. > > Note on style: I've generally placed declarations as allowed by C99, > closest to point of use. Let me know if you'd prefer otherwise. > > 1. Improve ELF error reporting applied > 2. Add .BTF section using libelf > > This shows the minimal amount of code needed to drive libelf. However, > it leaves layout up to libelf, which is almost certainly not wanted. > > As an unexpcted side-effect, vmlinux is larger than before. It seems > llvm-objcopy likes to trim down .strtab. We have to test this thoroughly, I'm adding support to gcc's -gdwarf-5 DW_AT_data_bit_offset, I think I should get that done and release 1.20, if some bug is still left on that new code, we can just fallback to -gdwarf-4. Then get back to the last 2 patches in your series, ok? - Arnaldo > 3. Manually lay out updated ELF sections > > This does full layout of new and updated ELF sections. If the update > ELF sections were not the last ones in the file by offset, then it can > leave gaps between sections. > > 4. Align .BTF section to 8 bytes > > This was my original aim. > > Regards. > > Giuliano Procida (4): > btf_encoder: Improve ELF error reporting > btf_encoder: Add .BTF section using libelf > btf_encoder: Manually lay out updated ELF sections > btf_encoder: Align .BTF section to 8 bytes > > libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 175 insertions(+), 47 deletions(-) > > -- > 2.30.0.280.ga3ce27912f-goog >
Hi. On Wed, 27 Jan 2021 at 14:06, Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > > Em Mon, Jan 25, 2021 at 01:06:21PM +0000, Giuliano Procida escreveu: > > Hi. > > > > This follows on from my change to improve the error handling around > > llvm-objcopy in libbtf.c. > > > > Note on recipients: Please let me know if I should adjust To or CC. > > > > Note on style: I've generally placed declarations as allowed by C99, > > closest to point of use. Let me know if you'd prefer otherwise. > > > > 1. Improve ELF error reporting > > applied > > > 2. Add .BTF section using libelf > > > > This shows the minimal amount of code needed to drive libelf. However, > > it leaves layout up to libelf, which is almost certainly not wanted. > > > > As an unexpcted side-effect, vmlinux is larger than before. It seems > > llvm-objcopy likes to trim down .strtab. > > We have to test this thoroughly, I'm adding support to gcc's -gdwarf-5 > DW_AT_data_bit_offset, I think I should get that done and release 1.20, > if some bug is still left on that new code, we can just fallback to > -gdwarf-4. > > Then get back to the last 2 patches in your series, ok? > That's fine. I've spent a little time digging into what llvm-objcopy (11.0.0) is doing. It turns out it will rewrite an ELF file even if you just do llvm-objcopy --dump-section .strtab=/dev/null elf_file, and even if the file is not writable. Our AOSP kernels have a lot symbols filtered out of the symbol table and perhaps this is what makes such a difference to the size of .strtab after llvm-objcopy has done its thing. I will try on a vanilla kernel. Giuliano. > - Arnaldo > > > 3. Manually lay out updated ELF sections > > > > This does full layout of new and updated ELF sections. If the update > > ELF sections were not the last ones in the file by offset, then it can > > leave gaps between sections. > > > > 4. Align .BTF section to 8 bytes > > > > This was my original aim. > > > > Regards. > > > > Giuliano Procida (4): > > btf_encoder: Improve ELF error reporting > > btf_encoder: Add .BTF section using libelf > > btf_encoder: Manually lay out updated ELF sections > > btf_encoder: Align .BTF section to 8 bytes > > > > libbtf.c | 222 +++++++++++++++++++++++++++++++++++++++++++------------ > > 1 file changed, 175 insertions(+), 47 deletions(-) > > > > -- > > 2.30.0.280.ga3ce27912f-goog > > > > -- > > - Arnaldo