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Bdragon28 (Brandon Bergren)
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User Since
Jan 11 2019, 6:48 AM (57 w, 3 d)

Recent Activity

Tue, Jan 28

Bdragon28 accepted D73532: [ELF][PPC32] Support --emit-relocs link of R_PPC_PLTREL24.

Looks correct to me, works great, and fixes the last lld-related problem I am aware of currently on FreeBSD powerpc32.

Tue, Jan 28, 10:58 AM · Restricted Project
Bdragon28 added a comment to D73532: [ELF][PPC32] Support --emit-relocs link of R_PPC_PLTREL24.

I am now able to load pf.ko on FreeBSD powerpc32 without it crashing.

Tue, Jan 28, 7:54 AM · Restricted Project

Sat, Jan 25

Bdragon28 created D73425: [PPC] Fix platform definitions when compiling FreeBSD powerpc64 as LE.
Sat, Jan 25, 10:43 PM · Restricted Project, Restricted Project
Bdragon28 accepted D73424: [ELF][PPC32] Support range extension thunk with addends.

This is necessary to run large programs like clang on FreeBSD powerpc32 when built with lld, because of REL24 branches in the crt startup code (done on purpose for object reusability reasons -- the csu objects need to work on both non-pic and pic, so they just use a plain bl and rely on the link editor to do a thunk if necessary.)

Sat, Jan 25, 10:21 PM · Restricted Project
Bdragon28 accepted D73399: [ELF][PPC32] Support canonical PLT.

Working great!

Sat, Jan 25, 5:56 PM · Restricted Project
Bdragon28 added a comment to D73399: [ELF][PPC32] Support canonical PLT.

This version looks very promising so far. Will do a full freebsd buildworld test / boot on G4. I expect this version to have fixed the issue, but will verify.

Sat, Jan 25, 3:32 PM · Restricted Project
Bdragon28 added a comment to D73399: [ELF][PPC32] Support canonical PLT.

Excellent! This looks like it fixed the FreeBSD putchar problem for me. I will test this with a full powerpc32 buildworld and report back.

Sat, Jan 25, 12:20 PM · Restricted Project

Fri, Jan 24

Bdragon28 accepted D73255: [ELF][PowerPC] Support R_PPC_COPY and R_PPC64_COPY.

While I ran into further problems on ppc32, I think it's just because there are further problems on ppc32 (unrelated to this one). At the very least this gets FreeBSD ppc32/lld10 as far as the rescue shell, which is great progress!

Fri, Jan 24, 8:31 AM · Restricted Project

Thu, Jan 23

Bdragon28 added a comment to D73255: [ELF][PowerPC] Support R_PPC_COPY and R_PPC64_COPY.

For anyone who is curious about this, copy relocations are especially needed on powerpc32, where they are used to implement global data (such as sharing a pointer between a .so and the main program) in situations where the main program's copy lives in .bss.

Thu, Jan 23, 9:25 AM · Restricted Project

Jan 7 2020

Bdragon28 added a comment to D72363: [PowerPC] Default ppc64 linux-gnu/freebsd to -fno-PIC.

I am definitely in favor of this change, as the defaulting to PIC has been causing headaches in the FreeBSD kernel.

Jan 7 2020, 2:54 PM · Restricted Project

Nov 29 2019

Bdragon28 added a comment to D70570: [PowerPC] Only use PLT annotations if using PIC relocation model.

On the FreeBSD kernel side, I put some time into working out the missing parts on ppc32 and slightly extending the kernel linker to support secure-plt PIC kernel modules. Working on that over at https://reviews.freebsd.org/D22608.

Nov 29 2019, 1:27 PM · Restricted Project

Nov 25 2019

Bdragon28 added a comment to D70570: [PowerPC] Only use PLT annotations if using PIC relocation model.

This doesn't seem quite sufficient for FreeBSD kernel modules. It's emitting R_PPC_REL24 instead of R_PPC_ADDR16_HA/R_PPC_ADDR16_LO pairs for stuff like memset and memcpy, which are unusable because we're running modules in KVA and the kernel text in the 32 bit DMAP. Still need to figure out why these are being emitted this way when using freestanding.

Nov 25 2019, 9:01 AM · Restricted Project

Aug 8 2019

Bdragon28 added a comment to D64906: [ELF][PPC] Allow PT_LOAD to have overlapping p_offset ranges.

It turns out I need the proper fix after all in my local tree, because lately I have been working on getting a working Petitboot loader binary, and that means I'm technically cross compiling code for ppc64le Linux. So yeah, it would be very nice to get this in.

Aug 8 2019, 10:58 AM · Restricted Project

May 14 2019

Bdragon28 added inline comments to D61792: [PPC] Fix 32-bit build of libunwind.
May 14 2019, 2:50 PM · Restricted Project, Restricted Project

May 7 2019

Bdragon28 added a comment to D61647: llvm-objdump: when ELF st_other field is set, print its value before symbol name.

So for ELF, you would want to do this logic INSTEAD of the hidden check immediately above.

May 7 2019, 4:46 PM · Restricted Project
Bdragon28 added a comment to D61647: llvm-objdump: when ELF st_other field is set, print its value before symbol name.

So basically, it's either printing nothing (if st_other is 0), .internal (if st_other is 1), .hidden (if st_other is 2), .protected (if st_other is 3), or hex (anything other than these exact st_other values.)

May 7 2019, 4:41 PM · Restricted Project
Bdragon28 added a comment to D61647: llvm-objdump: when ELF st_other field is set, print its value before symbol name.

The relevant binutils objdump logic is contained in bfd/elf.c, specifically the bfd_elf_print_symbol() function.

May 7 2019, 4:32 PM · Restricted Project

Jan 11 2019

Bdragon28 added a comment to D56586: [PPC64] Update LocalEntry from assigned symbols.

One particular place this is needed is to handle FreeBSD powerpc64 (ELFv2 experimental) libc's weak symbols / symbol aliasing, especially when using LLD (in my experience, binutils ld will partially compensate for this issue.)

Jan 11 2019, 7:34 AM · Restricted Project