From: Ian Rogers <irogers@google.com>
To: Stian Halseth <stian@itx.no>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Andreas Larsson <andreas@gaisler.com>,
"David S. Miller" <davem@davemloft.net>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Randy Dunlap <rdunlap@infradead.org>,
Magnus Lindholm <linmag7@gmail.com>,
linux-perf-users@vger.kernel.org, sparclinux@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 3/3] perf tools: Support sparc user register samples and dwarf unwinding
Date: Tue, 22 Sep 2026 13:31:42 -0700 [thread overview]
Message-ID: <CAP-5=fWNhJGHnRoz7FrwZO2mOZa4NCi5C3ZsFGrirAE0prj69w@mail.gmail.com> (raw)
In-Reply-To: <20260922201507.1719668-4-stian@itx.no>
On Tue, Sep 22, 2026 at 1:15 PM Stian Halseth <stian@itx.no> wrote:
>
> Add the sparc perf_regs tables and the EM_SPARC/EM_SPARCV9 dispatch for
> register names, masks, ip/sp and the perf-to-DWARF register mapping,
> plus the uapi header copy.
>
> For libdw unwinding, seed DWARF registers 16-31 (%l0-%l7, %i0-%i7) from
> the register save area at the top of the stack dump: the kernel flushes
> the sampled window there, and the CFI after `save` needs %i6 and %i7 to
> find the first caller. The dump base on sparc is the biased %sp, so
> read words from the dump with memcpy rather than an aligned
> dereference.
>
> Signed-off-by: Stian Halseth <stian@itx.no>
> ---
> tools/arch/sparc/include/uapi/asm/perf_regs.h | 33 +++++++++
> tools/perf/arch/sparc/include/perf_regs.h | 18 +++++
> tools/perf/check-headers.sh | 1 +
> tools/perf/util/dwarf-regs-arch/Build | 1 +
> .../util/dwarf-regs-arch/dwarf-regs-sparc.c | 12 ++++
> tools/perf/util/dwarf-regs.c | 4 ++
> tools/perf/util/include/dwarf-regs.h | 1 +
> tools/perf/util/perf-regs-arch/Build | 1 +
> .../util/perf-regs-arch/perf_regs_sparc.c | 69 +++++++++++++++++++
> tools/perf/util/perf_regs.c | 18 +++++
> tools/perf/util/perf_regs.h | 5 ++
> tools/perf/util/unwind-libdw.c | 41 ++++++++++-
> 12 files changed, 203 insertions(+), 1 deletion(-)
> create mode 100644 tools/arch/sparc/include/uapi/asm/perf_regs.h
> create mode 100644 tools/perf/arch/sparc/include/perf_regs.h
> create mode 100644 tools/perf/util/dwarf-regs-arch/dwarf-regs-sparc.c
> create mode 100644 tools/perf/util/perf-regs-arch/perf_regs_sparc.c
>
> diff --git a/tools/arch/sparc/include/uapi/asm/perf_regs.h b/tools/arch/sparc/include/uapi/asm/perf_regs.h
> new file mode 100644
> index 000000000000..17f14335d6c0
> --- /dev/null
> +++ b/tools/arch/sparc/include/uapi/asm/perf_regs.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +#ifndef _UAPI_ASM_SPARC_PERF_REGS_H
> +#define _UAPI_ASM_SPARC_PERF_REGS_H
> +
> +/*
> + * Mirrors struct pt_regs. O6 is %sp as held in the register, i.e. biased
> + * by 2047 for a 64-bit task.
> + */
> +enum perf_event_sparc_regs {
> + PERF_REG_SPARC_G0,
> + PERF_REG_SPARC_G1,
> + PERF_REG_SPARC_G2,
> + PERF_REG_SPARC_G3,
> + PERF_REG_SPARC_G4,
> + PERF_REG_SPARC_G5,
> + PERF_REG_SPARC_G6,
> + PERF_REG_SPARC_G7,
> + PERF_REG_SPARC_O0,
> + PERF_REG_SPARC_O1,
> + PERF_REG_SPARC_O2,
> + PERF_REG_SPARC_O3,
> + PERF_REG_SPARC_O4,
> + PERF_REG_SPARC_O5,
> + PERF_REG_SPARC_O6,
> + PERF_REG_SPARC_O7,
> + PERF_REG_SPARC_TSTATE,
> + PERF_REG_SPARC_PC,
> + PERF_REG_SPARC_NPC,
> + PERF_REG_SPARC_Y,
> + PERF_REG_SPARC_MAX
> +};
> +
> +#endif /* _UAPI_ASM_SPARC_PERF_REGS_H */
> diff --git a/tools/perf/arch/sparc/include/perf_regs.h b/tools/perf/arch/sparc/include/perf_regs.h
> new file mode 100644
> index 000000000000..493fbff9ea16
> --- /dev/null
> +++ b/tools/perf/arch/sparc/include/perf_regs.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef ARCH_PERF_REGS_H
> +#define ARCH_PERF_REGS_H
> +
> +#include <stdlib.h>
> +#include <linux/types.h>
> +#include "../../../../arch/sparc/include/uapi/asm/perf_regs.h"
> +
> +#define PERF_REGS_MASK ((1ULL << PERF_REG_SPARC_MAX) - 1)
> +#define PERF_REGS_MAX PERF_REG_SPARC_MAX
> +
> +#ifdef __arch64__
> +#define PERF_SAMPLE_REGS_ABI PERF_SAMPLE_REGS_ABI_64
> +#else
> +#define PERF_SAMPLE_REGS_ABI PERF_SAMPLE_REGS_ABI_32
> +#endif
> +
> +#endif /* ARCH_PERF_REGS_H */
> diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
> index 531c0e0e84df..f144590f5082 100755
> --- a/tools/perf/check-headers.sh
> +++ b/tools/perf/check-headers.sh
> @@ -42,6 +42,7 @@ declare -a FILES=(
> "arch/mips/include/uapi/asm/perf_regs.h"
> "arch/powerpc/include/uapi/asm/perf_regs.h"
> "arch/s390/include/uapi/asm/perf_regs.h"
> + "arch/sparc/include/uapi/asm/perf_regs.h"
> "arch/x86/include/uapi/asm/perf_regs.h"
> "arch/x86/include/uapi/asm/kvm.h"
> "arch/x86/include/uapi/asm/svm.h"
> diff --git a/tools/perf/util/dwarf-regs-arch/Build b/tools/perf/util/dwarf-regs-arch/Build
> index ceb68ae86fd8..bda944029046 100644
> --- a/tools/perf/util/dwarf-regs-arch/Build
> +++ b/tools/perf/util/dwarf-regs-arch/Build
> @@ -6,4 +6,5 @@ perf-util-$(CONFIG_LIBDW) += dwarf-regs-mips.o
> perf-util-$(CONFIG_LIBDW) += dwarf-regs-powerpc.o
> perf-util-$(CONFIG_LIBDW) += dwarf-regs-riscv.o
> perf-util-$(CONFIG_LIBDW) += dwarf-regs-s390.o
> +perf-util-$(CONFIG_LIBDW) += dwarf-regs-sparc.o
> perf-util-$(CONFIG_LIBDW) += dwarf-regs-x86.o
> diff --git a/tools/perf/util/dwarf-regs-arch/dwarf-regs-sparc.c b/tools/perf/util/dwarf-regs-arch/dwarf-regs-sparc.c
> new file mode 100644
> index 000000000000..dd0c80e29764
> --- /dev/null
> +++ b/tools/perf/util/dwarf-regs-arch/dwarf-regs-sparc.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <errno.h>
> +#include <dwarf-regs.h>
> +#include "../../../arch/sparc/include/uapi/asm/perf_regs.h"
> +
> +int __get_dwarf_regnum_for_perf_regnum_sparc(int perf_regnum)
> +{
> + if (perf_regnum < PERF_REG_SPARC_G0 || perf_regnum > PERF_REG_SPARC_O7)
> + return -ENOENT;
> +
> + return perf_regnum;
> +}
> diff --git a/tools/perf/util/dwarf-regs.c b/tools/perf/util/dwarf-regs.c
> index 797f455eba0d..df9200c31aaa 100644
> --- a/tools/perf/util/dwarf-regs.c
> +++ b/tools/perf/util/dwarf-regs.c
> @@ -217,6 +217,10 @@ int get_dwarf_regnum_for_perf_regnum(int perf_regnum, unsigned int machine,
> case EM_S390:
> reg = __get_dwarf_regnum_for_perf_regnum_s390(perf_regnum);
> break;
> + case EM_SPARC:
> + case EM_SPARCV9:
> + reg = __get_dwarf_regnum_for_perf_regnum_sparc(perf_regnum);
> + break;
> case EM_LOONGARCH:
> reg = __get_dwarf_regnum_for_perf_regnum_loongarch(perf_regnum);
> break;
> diff --git a/tools/perf/util/include/dwarf-regs.h b/tools/perf/util/include/dwarf-regs.h
> index 46a764cf322f..4a02f30c5604 100644
> --- a/tools/perf/util/include/dwarf-regs.h
> +++ b/tools/perf/util/include/dwarf-regs.h
> @@ -113,6 +113,7 @@ int __get_dwarf_regnum_for_perf_regnum_loongarch(int perf_regnum);
> int __get_dwarf_regnum_for_perf_regnum_powerpc(int perf_regnum);
> int __get_dwarf_regnum_for_perf_regnum_riscv(int perf_regnum);
> int __get_dwarf_regnum_for_perf_regnum_s390(int perf_regnum);
> +int __get_dwarf_regnum_for_perf_regnum_sparc(int perf_regnum);
> int __get_dwarf_regnum_for_perf_regnum_mips(int perf_regnum);
>
> /*
> diff --git a/tools/perf/util/perf-regs-arch/Build b/tools/perf/util/perf-regs-arch/Build
> index be95402aa540..47220a2f2dae 100644
> --- a/tools/perf/util/perf-regs-arch/Build
> +++ b/tools/perf/util/perf-regs-arch/Build
> @@ -6,4 +6,5 @@ perf-util-y += perf_regs_mips.o
> perf-util-y += perf_regs_powerpc.o
> perf-util-y += perf_regs_riscv.o
> perf-util-y += perf_regs_s390.o
> +perf-util-y += perf_regs_sparc.o
> perf-util-y += perf_regs_x86.o
> diff --git a/tools/perf/util/perf-regs-arch/perf_regs_sparc.c b/tools/perf/util/perf-regs-arch/perf_regs_sparc.c
> new file mode 100644
> index 000000000000..36d84ddd3a48
> --- /dev/null
> +++ b/tools/perf/util/perf-regs-arch/perf_regs_sparc.c
> @@ -0,0 +1,69 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "../perf_regs.h"
> +#include "../../arch/sparc/include/perf_regs.h"
> +
> +uint64_t __perf_reg_mask_sparc(bool intr __maybe_unused)
> +{
> + return PERF_REGS_MASK;
> +}
> +
> +const char *__perf_reg_name_sparc(int id)
> +{
> + switch (id) {
> + case PERF_REG_SPARC_G0:
> + return "g0";
> + case PERF_REG_SPARC_G1:
> + return "g1";
> + case PERF_REG_SPARC_G2:
> + return "g2";
> + case PERF_REG_SPARC_G3:
> + return "g3";
> + case PERF_REG_SPARC_G4:
> + return "g4";
> + case PERF_REG_SPARC_G5:
> + return "g5";
> + case PERF_REG_SPARC_G6:
> + return "g6";
> + case PERF_REG_SPARC_G7:
> + return "g7";
> + case PERF_REG_SPARC_O0:
> + return "o0";
> + case PERF_REG_SPARC_O1:
> + return "o1";
> + case PERF_REG_SPARC_O2:
> + return "o2";
> + case PERF_REG_SPARC_O3:
> + return "o3";
> + case PERF_REG_SPARC_O4:
> + return "o4";
> + case PERF_REG_SPARC_O5:
> + return "o5";
> + case PERF_REG_SPARC_O6:
> + return "sp";
> + case PERF_REG_SPARC_O7:
> + return "o7";
> + case PERF_REG_SPARC_TSTATE:
> + return "tstate";
> + case PERF_REG_SPARC_PC:
> + return "pc";
> + case PERF_REG_SPARC_NPC:
> + return "npc";
> + case PERF_REG_SPARC_Y:
> + return "y";
> + default:
> + return NULL;
> + }
> +
> + return NULL;
> +}
> +
> +uint64_t __perf_reg_ip_sparc(void)
> +{
> + return PERF_REG_SPARC_PC;
> +}
> +
> +uint64_t __perf_reg_sp_sparc(void)
> +{
> + return PERF_REG_SPARC_O6;
> +}
> diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
> index 558c143abbab..5880b54fd7dc 100644
> --- a/tools/perf/util/perf_regs.c
> +++ b/tools/perf/util/perf_regs.c
> @@ -68,6 +68,10 @@ uint64_t perf_intr_reg_mask(uint16_t e_machine)
> case EM_S390:
> mask = __perf_reg_mask_s390(/*intr=*/true);
> break;
> + case EM_SPARC:
> + case EM_SPARCV9:
> + mask = __perf_reg_mask_sparc(/*intr=*/true);
> + break;
> case EM_386:
> case EM_X86_64:
> mask = __perf_reg_mask_x86(/*intr=*/true);
> @@ -111,6 +115,10 @@ uint64_t perf_user_reg_mask(uint16_t e_machine)
> case EM_S390:
> mask = __perf_reg_mask_s390(/*intr=*/false);
> break;
> + case EM_SPARC:
> + case EM_SPARCV9:
> + mask = __perf_reg_mask_sparc(/*intr=*/false);
> + break;
> case EM_386:
> case EM_X86_64:
> mask = __perf_reg_mask_x86(/*intr=*/false);
> @@ -154,6 +162,10 @@ const char *perf_reg_name(int id, uint16_t e_machine, uint32_t e_flags)
> case EM_S390:
> reg_name = __perf_reg_name_s390(id);
> break;
> + case EM_SPARC:
> + case EM_SPARCV9:
> + reg_name = __perf_reg_name_sparc(id);
> + break;
> case EM_386:
> case EM_X86_64:
> reg_name = __perf_reg_name_x86(id);
> @@ -215,6 +227,9 @@ uint64_t perf_arch_reg_ip(uint16_t e_machine)
> return __perf_reg_ip_riscv();
> case EM_S390:
> return __perf_reg_ip_s390();
> + case EM_SPARC:
> + case EM_SPARCV9:
> + return __perf_reg_ip_sparc();
> case EM_386:
> case EM_X86_64:
> return __perf_reg_ip_x86();
> @@ -244,6 +259,9 @@ uint64_t perf_arch_reg_sp(uint16_t e_machine)
> return __perf_reg_sp_riscv();
> case EM_S390:
> return __perf_reg_sp_s390();
> + case EM_SPARC:
> + case EM_SPARCV9:
> + return __perf_reg_sp_sparc();
> case EM_386:
> case EM_X86_64:
> return __perf_reg_sp_x86();
> diff --git a/tools/perf/util/perf_regs.h b/tools/perf/util/perf_regs.h
> index 79be2b791509..3f453d910aa4 100644
> --- a/tools/perf/util/perf_regs.h
> +++ b/tools/perf/util/perf_regs.h
> @@ -65,6 +65,11 @@ uint64_t __perf_reg_ip_s390(void);
> uint64_t __perf_reg_sp_s390(void);
> int __perf_sdt_arg_parse_op_s390(char *old_op, char **new_op);
>
> +uint64_t __perf_reg_mask_sparc(bool intr);
> +const char *__perf_reg_name_sparc(int id);
> +uint64_t __perf_reg_ip_sparc(void);
> +uint64_t __perf_reg_sp_sparc(void);
> +
> int __perf_sdt_arg_parse_op_x86(char *old_op, char **new_op);
> uint64_t __perf_reg_mask_x86(bool intr);
> const char *__perf_reg_name_x86(int id);
> diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
> index 63a5c2253174..62484bcd5cd3 100644
> --- a/tools/perf/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw.c
> @@ -4,7 +4,9 @@
> #include <elfutils/libdw.h>
> #include <elfutils/libdwfl.h>
> #include <inttypes.h>
> +#include <elf.h>
> #include <errno.h>
> +#include <string.h>
> #include "debug.h"
> #include "dso.h"
> #include <dwarf-regs.h>
> @@ -261,12 +263,44 @@ static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *
> }
>
> offset = addr - start;
> - *result = *(Dwarf_Word *)&stack->data[offset];
> + memcpy(result, &stack->data[offset], sizeof(*result));
> pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
> addr, (unsigned long)*result, offset);
> return true;
> }
>
> +/*
> + * The sampled window's %l and %i registers (DWARF 16-31) are not in the
> + * sample; the kernel flushed them to the register save area at the top of
> + * the dumped stack.
> + */
> +static void libdw_set_sparc_window_registers(struct unwind_info *ui,
> + struct regs_dump *user_regs,
> + Dwarf_Word *dwarf_regs)
> +{
> + struct stack_dump *stack = &ui->sample->user_stack;
> + bool abi64 = user_regs->abi == PERF_SAMPLE_REGS_ABI_64;
> + size_t wsize = abi64 ? sizeof(u64) : sizeof(u32);
> + u64 sp, offset = abi64 ? 2047 : 0;
> +
> + if (perf_reg_value(&sp, user_regs, perf_arch_reg_sp(ui->e_machine)))
> + return;
> + if (offset + 16 * wsize > stack->size)
> + return;
> +
> + for (int i = 0; i < 16; i++) {
> + const char *p = &stack->data[offset + i * wsize];
> + u32 w32;
> +
> + if (abi64) {
> + memcpy(&dwarf_regs[16 + i], p, sizeof(u64));
> + } else {
> + memcpy(&w32, p, sizeof(w32));
> + dwarf_regs[16 + i] = w32;
> + }
> + }
> +}
> +
> static bool libdw_set_initial_registers(Dwfl_Thread *thread, void *arg)
> {
> struct dwfl_ui_thread_info *dwfl_ui_ti = arg;
> @@ -276,6 +310,7 @@ static bool libdw_set_initial_registers(Dwfl_Thread *thread, void *arg)
> int max_dwarf_reg = 0;
> bool ret;
> uint16_t e_machine = ui->e_machine;
> + bool is_sparc = e_machine == EM_SPARC || e_machine == EM_SPARCV9;
> int e_flags = ui->e_flags;
> uint64_t ip_perf_reg = perf_arch_reg_ip(e_machine);
> Dwarf_Word val = 0;
> @@ -295,6 +330,8 @@ static bool libdw_set_initial_registers(Dwfl_Thread *thread, void *arg)
> max_dwarf_reg = dwarf_reg;
> }
> }
> + if (is_sparc && max_dwarf_reg < 31)
> + max_dwarf_reg = 31;
Thanks! I think these are great patches! At this point in the code are
you setting max_dwarf_reg so that there's space for the window
registers? I think adding a comment here for clarity would be
worthwhile as it matches up with libdw_set_sparc_window_registers.
Thanks,
Ian
>
> dwarf_regs = calloc(max_dwarf_reg + 1, sizeof(*dwarf_regs));
> if (!dwarf_regs)
> @@ -313,6 +350,8 @@ static bool libdw_set_initial_registers(Dwfl_Thread *thread, void *arg)
> }
> }
> }
> + if (is_sparc)
> + libdw_set_sparc_window_registers(ui, user_regs, dwarf_regs);
> if (perf_reg_value(&val, user_regs, ip_perf_reg) == 0)
> dwfl_thread_state_register_pc(thread, val);
>
> --
> 2.55.0
>
next prev parent reply other threads:[~2026-09-22 20:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 20:15 [RFC PATCH v2 0/3] perf: sparc64 user regs and stack dump, with an arch hook Stian Halseth
2026-09-22 20:15 ` [RFC PATCH v2 1/3] perf/core: Let an arch prepare the user stack before it is dumped Stian Halseth
2026-09-22 20:15 ` [RFC PATCH v2 2/3] sparc64: Support PERF_SAMPLE_REGS_USER and PERF_SAMPLE_STACK_USER Stian Halseth
2026-09-22 20:15 ` [RFC PATCH v2 3/3] perf tools: Support sparc user register samples and dwarf unwinding Stian Halseth
2026-09-22 20:31 ` Ian Rogers [this message]
2026-09-22 21:09 ` Stian Halseth
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