Re: [PATCH v2 0/8] perf libunwind multiple remote support

From: Namhyung Kim <namhyung@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: 9erthalion6@gmail.com, acme@kernel.org, adrian.hunter@intel.com,
	alex@ghiti.fr, alexander.shishkin@linux.intel.com,
	andrew.jones@oss.qualcomm.com, aou@eecs.berkeley.edu,
	atrajeev@linux.ibm.com, blakejones@google.com, ctshao@google.com,
	dapeng1.mi@linux.intel.com, howardchu95@gmail.com,
	james.clark@linaro.org, john.g.garry@oracle.com,
	jolsa@kernel.org, leo.yan@linux.dev, libunwind-devel@nongnu.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
	linux-riscv@lists.infradead.org, mingo@redhat.com,
	palmer@dabbelt.com, peterz@infradead.org, pjw@kernel.org,
	shimin.guo@skydio.com, tglozar@redhat.com, tmricht@linux.ibm.com,
	will@kernel.org, yuzhuo@google.com
Subject: Re: [PATCH v2 0/8] perf libunwind multiple remote support
Date: Thu, 19 Mar 2026 14:39:07 -0700	[thread overview]
Message-ID: <abxs-2rozL1tBEO1@google.com> (raw)
In-Reply-To: <20260305221927.3237145-1-irogers@google.com>

Hi Ian,

On Thu, Mar 05, 2026 at 02:19:19PM -0800, Ian Rogers wrote:
> Fix the libunwind build for when libdw and libunwind are feature
> detected, currently failing with a duplicate symbol.
> 
> Refactor the libunwind support so that whenever a remote target is
> available, perf functions using the ELF machine can use that remote
> target regardless of what the host/local machine is. Migrate existing
> libunwind supported architectures like powerpc, arm64 and loongarch so
> that they can work in a cross-architecture way. Add support for
> RISC-V. Make the code more regular in function names, etc. and avoid
> including a C-file. This increases the lines of code. It is similar in
> style to the unwind-libdw implementation. It is hoped that the more
> uniform nature of the code with help with refactoring the perf
> registers for SIMD/APX support.
> 
> Aside from local host testing these patches are under tested, in part
> as I'm failing to see how to build libunwind with support for multiple
> remote targets. Please could I get help in testing.

It seems libunwind project is not actively maintained.  Assuming libdw
unwinding is performant enough, we may want to get rid of libunwind
support.

Thanks,
Namhyung

> 
> v2: Move two fixes patches to position 1 and 2 in the series. Fix
>     struct naming inconsistency, Andrew Jones
>     <andrew.jones@oss.qualcomm.com>. Fix other inconsistencies and
>     potential non-x86 build issues.
> 
> v1: https://lore.kernel.org/lkml/20260224142938.26088-1-irogers@google.com/
> 
> Ian Rogers (8):
>   perf unwind: Refactor get_entries to allow dynamic libdw/libunwind
>     selection
>   perf build loongarch: Remove reference to missing file
>   tools build: Deduplicate test-libunwind for different architectures
>   perf build: Be more programmatic when setting up libunwind variables
>   perf unwind-libunwind: Make libunwind register reading cross platform
>   perf unwind-libunwind: Move flush/finish access out of local
>   perf unwind-libunwind: Remove libunwind-local
>   perf unwind-libunwind: Add RISC-V libunwind support
> 
>  tools/build/feature/Makefile                  |  38 +-
>  tools/build/feature/test-libunwind-aarch64.c  |  27 -
>  tools/build/feature/test-libunwind-arm.c      |  28 -
>  .../test-libunwind-debug-frame-aarch64.c      |  17 -
>  .../feature/test-libunwind-debug-frame-arm.c  |  17 -
>  .../feature/test-libunwind-debug-frame.c      |   1 -
>  tools/build/feature/test-libunwind-x86.c      |  28 -
>  tools/build/feature/test-libunwind-x86_64.c   |  28 -
>  tools/build/feature/test-libunwind.c          |   1 -
>  tools/perf/Makefile.config                    | 215 ++---
>  tools/perf/arch/arm/util/Build                |   2 -
>  tools/perf/arch/arm/util/unwind-libunwind.c   |  50 --
>  tools/perf/arch/arm64/util/Build              |   1 -
>  tools/perf/arch/arm64/util/unwind-libunwind.c |  17 -
>  tools/perf/arch/loongarch/util/Build          |   3 -
>  .../arch/loongarch/util/unwind-libunwind.c    |  82 --
>  tools/perf/arch/mips/Build                    |   1 -
>  tools/perf/arch/mips/util/Build               |   1 -
>  tools/perf/arch/mips/util/unwind-libunwind.c  |  22 -
>  tools/perf/arch/powerpc/util/Build            |   1 -
>  .../perf/arch/powerpc/util/unwind-libunwind.c |  92 --
>  tools/perf/arch/x86/util/Build                |   3 -
>  tools/perf/arch/x86/util/unwind-libunwind.c   | 115 ---
>  tools/perf/builtin-inject.c                   |   4 +
>  tools/perf/builtin-report.c                   |   4 +
>  tools/perf/builtin-script.c                   |   4 +
>  tools/perf/util/Build                         |   5 +-
>  tools/perf/util/libunwind-arch/Build          |  11 +
>  .../perf/util/libunwind-arch/libunwind-arch.c | 319 +++++++
>  .../perf/util/libunwind-arch/libunwind-arch.h | 296 +++++++
>  .../perf/util/libunwind-arch/libunwind-arm.c  | 290 ++++++
>  .../util/libunwind-arch/libunwind-arm64.c     | 289 ++++++
>  .../perf/util/libunwind-arch/libunwind-i386.c | 312 +++++++
>  .../util/libunwind-arch/libunwind-loongarch.c | 297 +++++++
>  .../perf/util/libunwind-arch/libunwind-mips.c | 299 +++++++
>  .../util/libunwind-arch/libunwind-ppc32.c     | 301 +++++++
>  .../util/libunwind-arch/libunwind-ppc64.c     | 303 +++++++
>  .../util/libunwind-arch/libunwind-riscv.c     | 297 +++++++
>  .../perf/util/libunwind-arch/libunwind-s390.c | 299 +++++++
>  .../util/libunwind-arch/libunwind-x86_64.c    | 320 +++++++
>  tools/perf/util/libunwind/arm64.c             |  40 -
>  tools/perf/util/libunwind/x86_32.c            |  41 -
>  tools/perf/util/maps.c                        |  29 +-
>  tools/perf/util/maps.h                        |   4 +-
>  tools/perf/util/symbol_conf.h                 |  15 +
>  tools/perf/util/thread.c                      |  29 +-
>  tools/perf/util/unwind-libdw.c                |   2 +-
>  tools/perf/util/unwind-libunwind-local.c      | 832 ------------------
>  tools/perf/util/unwind-libunwind.c            | 679 ++++++++++++--
>  tools/perf/util/unwind.c                      | 102 +++
>  tools/perf/util/unwind.h                      |  56 +-
>  51 files changed, 4536 insertions(+), 1733 deletions(-)
>  delete mode 100644 tools/build/feature/test-libunwind-aarch64.c
>  delete mode 100644 tools/build/feature/test-libunwind-arm.c
>  delete mode 100644 tools/build/feature/test-libunwind-debug-frame-aarch64.c
>  delete mode 100644 tools/build/feature/test-libunwind-debug-frame-arm.c
>  delete mode 100644 tools/build/feature/test-libunwind-x86.c
>  delete mode 100644 tools/build/feature/test-libunwind-x86_64.c
>  delete mode 100644 tools/perf/arch/arm/util/unwind-libunwind.c
>  delete mode 100644 tools/perf/arch/arm64/util/unwind-libunwind.c
>  delete mode 100644 tools/perf/arch/loongarch/util/unwind-libunwind.c
>  delete mode 100644 tools/perf/arch/mips/Build
>  delete mode 100644 tools/perf/arch/mips/util/Build
>  delete mode 100644 tools/perf/arch/mips/util/unwind-libunwind.c
>  delete mode 100644 tools/perf/arch/powerpc/util/unwind-libunwind.c
>  delete mode 100644 tools/perf/arch/x86/util/unwind-libunwind.c
>  create mode 100644 tools/perf/util/libunwind-arch/Build
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-arch.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-arch.h
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-arm.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-arm64.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-i386.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-loongarch.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-mips.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-ppc32.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-ppc64.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-riscv.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-s390.c
>  create mode 100644 tools/perf/util/libunwind-arch/libunwind-x86_64.c
>  delete mode 100644 tools/perf/util/libunwind/arm64.c
>  delete mode 100644 tools/perf/util/libunwind/x86_32.c
>  delete mode 100644 tools/perf/util/unwind-libunwind-local.c
>  create mode 100644 tools/perf/util/unwind.c
> 
> -- 
> 2.53.0.473.g4a7958ca14-goog
> 