]> git.ipfire.org Git - thirdparty/linux.git/commitdiff
perf dwarf-regs: Add get_dwarf_regnum_for_perf_regnum() and use for x86 unwinding
authorIan Rogers <irogers@google.com>
Sat, 17 Jan 2026 05:28:38 +0000 (21:28 -0800)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Tue, 20 Jan 2026 18:43:56 +0000 (15:43 -0300)
Add a utility to map a perf register number to a DWARF register number
for a particular ELF machine type.

Create a generic unwind-libdw initial register initialization routine
that uses this function and thereby avoids arch specific
initialization. The unwind-libdw code does:

1) compute the maximum DWARF register from the set of sampled user registers,
2) allocates a set of DWARF registers,
3) copies the sample registers into the appropriate DWARF registers.

This generic solution is initially implemented for use with x86 as
only get_dwarf_regnum_for_perf_regnum() support for x86 is currently present.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Aditya Bodkhe <aditya.b1@linux.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.ibm.com>
Cc: Chun-Tse Shao <ctshao@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Haibo Xu <haibo1.xu@intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Krzysztof Ɓopatowski <krzysztof.m.lopatowski@gmail.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Wielaard <mark@klomp.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergei Trofimovich <slyich@gmail.com>
Cc: Shimin Guo <shimin.guo@skydio.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/util/dwarf-regs-arch/dwarf-regs-x86.c
tools/perf/util/dwarf-regs.c
tools/perf/util/include/dwarf-regs.h
tools/perf/util/unwind-libdw-arch/Build
tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c [deleted file]
tools/perf/util/unwind-libdw.c
tools/perf/util/unwind-libdw.h

index f0c42e4d7423a374ab8c6e2395ff4e9c8f3801f7..cadef120aeb47cf16e02e6f55ef7031adcb7f50c 100644 (file)
@@ -10,6 +10,7 @@
 #include <string.h> /* for strcmp */
 #include <linux/kernel.h> /* for ARRAY_SIZE */
 #include <dwarf-regs.h>
+#include "../../../arch/x86/include/uapi/asm/perf_regs.h"
 
 struct dwarf_regs_idx {
        const char *name;
@@ -163,3 +164,97 @@ int __get_dwarf_regnum_x86_64(const char *name)
 {
        return get_regnum(x86_64_regidx_table, ARRAY_SIZE(x86_64_regidx_table), name);
 }
+
+int __get_dwarf_regnum_for_perf_regnum_i386(int perf_regnum)
+{
+       static const int dwarf_i386_regnums[] = {
+               [PERF_REG_X86_AX] = 0,
+               [PERF_REG_X86_BX] = 3,
+               [PERF_REG_X86_CX] = 1,
+               [PERF_REG_X86_DX] = 2,
+               [PERF_REG_X86_SI] = 6,
+               [PERF_REG_X86_DI] = 7,
+               [PERF_REG_X86_BP] = 5,
+               [PERF_REG_X86_SP] = 4,
+               [PERF_REG_X86_IP] = 8,
+               [PERF_REG_X86_FLAGS] = 9,
+               [PERF_REG_X86_CS] = 41,
+               [PERF_REG_X86_SS] = 42,
+               [PERF_REG_X86_DS] = 43,
+               [PERF_REG_X86_ES] = 40,
+               [PERF_REG_X86_FS] = 44,
+               [PERF_REG_X86_GS] = 45,
+               [PERF_REG_X86_XMM0] = 21,
+               [PERF_REG_X86_XMM1] = 22,
+               [PERF_REG_X86_XMM2] = 23,
+               [PERF_REG_X86_XMM3] = 24,
+               [PERF_REG_X86_XMM4] = 25,
+               [PERF_REG_X86_XMM5] = 26,
+               [PERF_REG_X86_XMM6] = 27,
+               [PERF_REG_X86_XMM7] = 28,
+       };
+
+       if (perf_regnum == 0)
+               return 0;
+
+       if (perf_regnum <  0 || perf_regnum > (int)ARRAY_SIZE(dwarf_i386_regnums) ||
+           dwarf_i386_regnums[perf_regnum] == 0)
+               return -ENOENT;
+
+       return dwarf_i386_regnums[perf_regnum];
+}
+
+int __get_dwarf_regnum_for_perf_regnum_x86_64(int perf_regnum)
+{
+       static const int dwarf_x86_64_regnums[] = {
+               [PERF_REG_X86_AX] = 0,
+               [PERF_REG_X86_BX] = 3,
+               [PERF_REG_X86_CX] = 2,
+               [PERF_REG_X86_DX] = 1,
+               [PERF_REG_X86_SI] = 4,
+               [PERF_REG_X86_DI] = 5,
+               [PERF_REG_X86_BP] = 6,
+               [PERF_REG_X86_SP] = 7,
+               [PERF_REG_X86_IP] = 16,
+               [PERF_REG_X86_FLAGS] = 49,
+               [PERF_REG_X86_CS] = 51,
+               [PERF_REG_X86_SS] = 52,
+               [PERF_REG_X86_DS] = 53,
+               [PERF_REG_X86_ES] = 50,
+               [PERF_REG_X86_FS] = 54,
+               [PERF_REG_X86_GS] = 55,
+               [PERF_REG_X86_R8] = 8,
+               [PERF_REG_X86_R9] = 9,
+               [PERF_REG_X86_R10] = 10,
+               [PERF_REG_X86_R11] = 11,
+               [PERF_REG_X86_R12] = 12,
+               [PERF_REG_X86_R13] = 13,
+               [PERF_REG_X86_R14] = 14,
+               [PERF_REG_X86_R15] = 15,
+               [PERF_REG_X86_XMM0] = 17,
+               [PERF_REG_X86_XMM1] = 18,
+               [PERF_REG_X86_XMM2] = 19,
+               [PERF_REG_X86_XMM3] = 20,
+               [PERF_REG_X86_XMM4] = 21,
+               [PERF_REG_X86_XMM5] = 22,
+               [PERF_REG_X86_XMM6] = 23,
+               [PERF_REG_X86_XMM7] = 24,
+               [PERF_REG_X86_XMM8] = 25,
+               [PERF_REG_X86_XMM9] = 26,
+               [PERF_REG_X86_XMM10] = 27,
+               [PERF_REG_X86_XMM11] = 28,
+               [PERF_REG_X86_XMM12] = 29,
+               [PERF_REG_X86_XMM13] = 30,
+               [PERF_REG_X86_XMM14] = 31,
+               [PERF_REG_X86_XMM15] = 32,
+       };
+
+       if (perf_regnum == 0)
+               return 0;
+
+       if (perf_regnum <  0 || perf_regnum > (int)ARRAY_SIZE(dwarf_x86_64_regnums) ||
+           dwarf_x86_64_regnums[perf_regnum] == 0)
+               return -ENOENT;
+
+       return dwarf_x86_64_regnums[perf_regnum];
+}
index ef249dd589e3717086b273a4d2c8f2ff0e7f33e6..1f7d892612dfe58e5bb42d6380e6aab1b407a459 100644 (file)
@@ -103,3 +103,58 @@ int get_dwarf_regnum(const char *name, unsigned int machine, unsigned int flags
        free(regname);
        return reg;
 }
+
+static int get_libdw_frame_nregs(unsigned int machine, unsigned int flags __maybe_unused)
+{
+       switch (machine) {
+       case EM_X86_64:
+               return 17;
+       case EM_386:
+               return 9;
+       case EM_ARM:
+               return 16;
+       case EM_AARCH64:
+               return 97;
+       case EM_CSKY:
+               return 38;
+       case EM_S390:
+               return 32;
+       case EM_PPC:
+       case EM_PPC64:
+               return 145;
+       case EM_RISCV:
+               return 66;
+       case EM_SPARC:
+       case EM_SPARCV9:
+               return 103;
+       case EM_LOONGARCH:
+               return 74;
+       default:
+               return 0;
+       }
+}
+
+int get_dwarf_regnum_for_perf_regnum(int perf_regnum, unsigned int machine,
+                                    unsigned int flags, bool only_libdw_supported)
+{
+       int reg;
+
+       switch (machine) {
+       case EM_X86_64:
+               reg = __get_dwarf_regnum_for_perf_regnum_x86_64(perf_regnum);
+               break;
+       case EM_386:
+               reg = __get_dwarf_regnum_for_perf_regnum_i386(perf_regnum);
+               break;
+       default:
+               pr_err("ELF MACHINE %x is not supported.\n", machine);
+               return -ENOENT;
+       }
+       if (reg >= 0 && only_libdw_supported) {
+               int nregs = get_libdw_frame_nregs(machine, flags);
+
+               if (reg >= nregs)
+                       reg = -ENOENT;
+       }
+       return reg;
+}
index bb5413b0fee4bf5105d05149da9f9800b082e122..00881f1d45d6f64608ae6de4523a68d9af466f45 100644 (file)
@@ -101,6 +101,8 @@ const char *get_dwarf_regstr(unsigned int n, unsigned int machine, unsigned int
 
 int __get_dwarf_regnum_i386(const char *name);
 int __get_dwarf_regnum_x86_64(const char *name);
+int __get_dwarf_regnum_for_perf_regnum_i386(int perf_regnum);
+int __get_dwarf_regnum_for_perf_regnum_x86_64(int perf_regnum);
 
 /*
  * get_dwarf_regnum - Returns DWARF regnum from register name
@@ -109,6 +111,12 @@ int __get_dwarf_regnum_x86_64(const char *name);
  */
 int get_dwarf_regnum(const char *name, unsigned int machine, unsigned int flags);
 
+/*
+ * get_dwarf_regnum - Returns DWARF regnum from perf register number.
+ */
+int get_dwarf_regnum_for_perf_regnum(int perf_regnum, unsigned int machine, unsigned int flags,
+                                    bool only_libdw_supported);
+
 void get_powerpc_regs(u32 raw_insn, int is_source, struct annotated_op_loc *op_loc);
 
 #else /* HAVE_LIBDW_SUPPORT */
index ef17a83a78136d7ab8d44c62d454742638ddf224..5b56820299531f2b743211b6eb20c9ca9c137bfb 100644 (file)
@@ -1,4 +1,3 @@
-perf-util-y += unwind-libdw-x86.o
 perf-util-y += unwind-libdw-arm.o
 perf-util-y += unwind-libdw-arm64.o
 perf-util-y += unwind-libdw-csky.o
diff --git a/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c b/tools/perf/util/unwind-libdw-arch/unwind-libdw-x86.c
deleted file mode 100644 (file)
index dd27545..0000000
+++ /dev/null
@@ -1,54 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <elfutils/libdwfl.h>
-#include "../arch/x86/include/uapi/asm/perf_regs.h"
-#include "util/unwind-libdw.h"
-#include "util/perf_regs.h"
-#include "util/sample.h"
-
-bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg)
-{
-       struct unwind_info *ui = arg;
-       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
-       Dwarf_Word dwarf_regs[17];
-       unsigned nregs;
-
-#define REG(r) ({                                              \
-       Dwarf_Word val = 0;                                     \
-       perf_reg_value(&val, user_regs, PERF_REG_X86_##r);      \
-       val;                                                    \
-})
-
-       if (user_regs->abi == PERF_SAMPLE_REGS_ABI_32) {
-               dwarf_regs[0] = REG(AX);
-               dwarf_regs[1] = REG(CX);
-               dwarf_regs[2] = REG(DX);
-               dwarf_regs[3] = REG(BX);
-               dwarf_regs[4] = REG(SP);
-               dwarf_regs[5] = REG(BP);
-               dwarf_regs[6] = REG(SI);
-               dwarf_regs[7] = REG(DI);
-               dwarf_regs[8] = REG(IP);
-               nregs = 9;
-       } else {
-               dwarf_regs[0]  = REG(AX);
-               dwarf_regs[1]  = REG(DX);
-               dwarf_regs[2]  = REG(CX);
-               dwarf_regs[3]  = REG(BX);
-               dwarf_regs[4]  = REG(SI);
-               dwarf_regs[5]  = REG(DI);
-               dwarf_regs[6]  = REG(BP);
-               dwarf_regs[7]  = REG(SP);
-               dwarf_regs[8]  = REG(R8);
-               dwarf_regs[9]  = REG(R9);
-               dwarf_regs[10] = REG(R10);
-               dwarf_regs[11] = REG(R11);
-               dwarf_regs[12] = REG(R12);
-               dwarf_regs[13] = REG(R13);
-               dwarf_regs[14] = REG(R14);
-               dwarf_regs[15] = REG(R15);
-               dwarf_regs[16] = REG(IP);
-               nregs = 17;
-       }
-
-       return dwfl_thread_state_registers(thread, 0, nregs, dwarf_regs);
-}
index c25190cdceb47f9c854a973953663c053e6462f2..055dab921442c014c1a810615360aee2e54d60f2 100644 (file)
@@ -6,6 +6,7 @@
 #include <errno.h>
 #include "debug.h"
 #include "dso.h"
+#include <dwarf-regs.h>
 #include "unwind.h"
 #include "unwind-libdw.h"
 #include "machine.h"
@@ -225,6 +226,59 @@ static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *
        return true;
 }
 
+static bool libdw_set_initial_registers_generic(Dwfl_Thread *thread, void *arg)
+{
+       struct unwind_info *ui = arg;
+       struct regs_dump *user_regs = perf_sample__user_regs(ui->sample);
+       Dwarf_Word *dwarf_regs;
+       int max_dwarf_reg = 0;
+       bool ret;
+       uint16_t e_machine = ui->e_machine;
+       int e_flags = 0;
+       uint64_t ip_perf_reg = perf_arch_reg_ip(e_machine);
+       Dwarf_Word val = 0;
+
+
+       /*
+        * For every possible perf register in the bitmap determine the dwarf
+        * register and use to compute the max.
+        */
+       for (int perf_reg = 0; perf_reg < 64; perf_reg++) {
+               if (user_regs->mask & (1ULL << perf_reg)) {
+                       int dwarf_reg =
+                               get_dwarf_regnum_for_perf_regnum(perf_reg, e_machine,
+                                                                e_flags,
+                                                                /*only_libdw_supported=*/true);
+                       if (dwarf_reg > max_dwarf_reg)
+                               max_dwarf_reg = dwarf_reg;
+               }
+       }
+
+       dwarf_regs = calloc(max_dwarf_reg + 1, sizeof(*dwarf_regs));
+       if (!dwarf_regs)
+               return false;
+
+       for (int perf_reg = 0; perf_reg < 64; perf_reg++) {
+               if (user_regs->mask & (1ULL << perf_reg)) {
+                       int dwarf_reg =
+                               get_dwarf_regnum_for_perf_regnum(perf_reg, e_machine,
+                                                                e_flags,
+                                                                /*only_libdw_supported=*/true);
+                       if (dwarf_reg >= 0) {
+                               val = 0;
+                               if (perf_reg_value(&val, user_regs, perf_reg) == 0)
+                                       dwarf_regs[dwarf_reg] = val;
+                       }
+               }
+       }
+       if (perf_reg_value(&val, user_regs, ip_perf_reg) == 0)
+               dwfl_thread_state_register_pc(thread, val);
+
+       ret = dwfl_thread_state_registers(thread, 0, max_dwarf_reg + 1, dwarf_regs);
+       free(dwarf_regs);
+       return ret;
+}
+
 #define DEFINE_DWFL_THREAD_CALLBACKS(arch)                           \
 static const Dwfl_Thread_Callbacks callbacks_##arch = {              \
        .next_thread           = next_thread,                        \
@@ -232,7 +286,12 @@ static const Dwfl_Thread_Callbacks callbacks_##arch = {              \
        .set_initial_registers = libdw_set_initial_registers_##arch, \
 }
 
-DEFINE_DWFL_THREAD_CALLBACKS(x86);
+static const Dwfl_Thread_Callbacks callbacks_generic = {
+       .next_thread           = next_thread,
+       .memory_read           = memory_read,
+       .set_initial_registers = libdw_set_initial_registers_generic,
+};
+
 DEFINE_DWFL_THREAD_CALLBACKS(arm);
 DEFINE_DWFL_THREAD_CALLBACKS(arm64);
 DEFINE_DWFL_THREAD_CALLBACKS(csky);
@@ -257,12 +316,8 @@ static const Dwfl_Thread_Callbacks *get_thread_callbacks(const char *arch)
                return &callbacks_riscv;
        else if (!strcmp(arch, "s390"))
                return &callbacks_s390;
-       else if (!strcmp(arch, "x86"))
-               return &callbacks_x86;
 
-       pr_err("Fail to get thread callbacks for arch %s, returns NULL\n",
-              arch);
-       return NULL;
+       return &callbacks_generic;
 }
 
 static int
@@ -301,6 +356,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
                        bool best_effort)
 {
        struct machine *machine = maps__machine(thread__maps(thread));
+       uint16_t e_machine = thread__e_machine(thread, machine);
        struct unwind_info *ui, ui_buf = {
                .sample         = data,
                .thread         = thread,
@@ -308,9 +364,9 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
                .cb             = cb,
                .arg            = arg,
                .max_stack      = max_stack,
+               .e_machine      = e_machine,
                .best_effort    = best_effort
        };
-       uint16_t e_machine = thread__e_machine(thread, machine);
        const char *arch = perf_env__arch(machine->env);
        Dwarf_Word ip;
        int err = -EINVAL, i;
index 574b29848cce31e6bfd93021f752b518cebf73b7..496e5898e7efa429b5b7e43ce134438b10d8d1cb 100644 (file)
@@ -9,7 +9,6 @@ struct machine;
 struct perf_sample;
 struct thread;
 
-bool libdw_set_initial_registers_x86(Dwfl_Thread *thread, void *arg);
 bool libdw_set_initial_registers_arm(Dwfl_Thread *thread, void *arg);
 bool libdw_set_initial_registers_arm64(Dwfl_Thread *thread, void *arg);
 bool libdw_set_initial_registers_csky(Dwfl_Thread *thread, void *arg);
@@ -28,6 +27,7 @@ struct unwind_info {
        void                    *arg;
        int                     max_stack;
        int                     idx;
+       uint16_t                e_machine;
        bool                    best_effort;
        struct unwind_entry     entries[];
 };