target/loongarch: Support QMP dump-guest-memory

Add the support needed for creating prstatus elf notes. This allows
us to use QMP dump-guest-memory.

Now ELF notes of LoongArch only supports general elf notes, LSX and
LASX is not supported, since it is mainly used to dump guest memory.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Tested-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240822065245.2286214-1-maobibo@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>

target/loongarch/arch_dump.c

@@ -0,0 +1,167 @@
+/*
+ * Support for writing ELF notes for LoongArch architectures
+ *
+ * Copyright (c) 2023 Loongarch Technology
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "elf.h"
+#include "sysemu/dump.h"
+#include "internals.h"
+
+/* struct user_pt_regs from arch/loongarch/include/uapi/asm/ptrace.h */
+struct loongarch_user_regs {
+    uint64_t gpr[32];
+    uint64_t pad1[1];
+    /* Special CSR registers. */
+    uint64_t csr_era;
+    uint64_t csr_badv;
+    uint64_t pad2[10];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct loongarch_user_regs) != 360);
+
+/* struct elf_prstatus from include/uapi/linux/elfcore.h */
+struct loongarch_elf_prstatus {
+    char pad1[32]; /* 32 == offsetof(struct elf_prstatus, pr_pid) */
+    uint32_t pr_pid;
+    /*
+     * 76 == offsetof(struct elf_prstatus, pr_reg) -
+     * offsetof(struct elf_prstatus, pr_ppid)
+     */
+    char pad2[76];
+    struct loongarch_user_regs pr_reg;
+    uint32_t pr_fpvalid;
+    char pad3[4];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct loongarch_elf_prstatus) != 480);
+
+/* struct user_fp_state from arch/loongarch/include/uapi/asm/ptrace.h */
+struct loongarch_fpu_struct {
+    uint64_t fpr[32];
+    uint64_t fcc;
+    unsigned int fcsr;
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct loongarch_fpu_struct) != 268);
+
+struct loongarch_note {
+    Elf64_Nhdr hdr;
+    char name[8]; /* align_up(sizeof("CORE"), 4) */
+    union {
+        struct loongarch_elf_prstatus prstatus;
+        struct loongarch_fpu_struct fpu;
+    };
+} QEMU_PACKED;
+
+#define LOONGARCH_NOTE_HEADER_SIZE offsetof(struct loongarch_note, prstatus)
+#define LOONGARCH_PRSTATUS_NOTE_SIZE                                          \
+    (LOONGARCH_NOTE_HEADER_SIZE + sizeof(struct loongarch_elf_prstatus))
+#define LOONGARCH_PRFPREG_NOTE_SIZE                                           \
+    (LOONGARCH_NOTE_HEADER_SIZE + sizeof(struct loongarch_fpu_struct))
+
+static void loongarch_note_init(struct loongarch_note *note, DumpState *s,
+                                const char *name, Elf64_Word namesz,
+                                Elf64_Word type, Elf64_Word descsz)
+{
+    memset(note, 0, sizeof(*note));
+
+    note->hdr.n_namesz = cpu_to_dump32(s, namesz);
+    note->hdr.n_descsz = cpu_to_dump32(s, descsz);
+    note->hdr.n_type = cpu_to_dump32(s, type);
+
+    memcpy(note->name, name, namesz);
+}
+
+static int loongarch_write_elf64_fprpreg(WriteCoreDumpFunction f,
+                                         CPULoongArchState *env, int cpuid,
+                                         DumpState *s)
+{
+    struct loongarch_note note;
+    int ret, i;
+
+    loongarch_note_init(&note, s, "CORE", 5, NT_PRFPREG, sizeof(note.fpu));
+    note.fpu.fcsr = cpu_to_dump64(s, env->fcsr0);
+
+    for (i = 0; i < 8; i++) {
+        note.fpu.fcc |= env->cf[i] << (8 * i);
+    }
+    note.fpu.fcc = cpu_to_dump64(s, note.fpu.fcc);
+
+    for (i = 0; i < 32; ++i) {
+        note.fpu.fpr[i] = cpu_to_dump64(s, env->fpr[i].vreg.UD[0]);
+    }
+
+    ret = f(&note, LOONGARCH_PRFPREG_NOTE_SIZE, s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+int loongarch_cpu_write_elf64_note(WriteCoreDumpFunction f, CPUState *cs,
+                                   int cpuid, DumpState *s)
+{
+    struct loongarch_note note;
+    CPULoongArchState *env = &LOONGARCH_CPU(cs)->env;
+    int ret, i;
+
+    loongarch_note_init(&note, s, "CORE", 5, NT_PRSTATUS,
+                        sizeof(note.prstatus));
+    note.prstatus.pr_pid = cpu_to_dump32(s, cpuid);
+    note.prstatus.pr_fpvalid = cpu_to_dump32(s, 1);
+
+    for (i = 0; i < 32; ++i) {
+        note.prstatus.pr_reg.gpr[i] = cpu_to_dump64(s, env->gpr[i]);
+    }
+    note.prstatus.pr_reg.csr_era  = cpu_to_dump64(s, env->CSR_ERA);
+    note.prstatus.pr_reg.csr_badv = cpu_to_dump64(s, env->CSR_BADV);
+    ret = f(&note, LOONGARCH_PRSTATUS_NOTE_SIZE, s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    ret = loongarch_write_elf64_fprpreg(f, env, cpuid, s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    return ret;
+}
+
+int cpu_get_dump_info(ArchDumpInfo *info,
+                      const GuestPhysBlockList *guest_phys_blocks)
+{
+    info->d_machine = EM_LOONGARCH;
+    info->d_endian = ELFDATA2LSB;
+    info->d_class = ELFCLASS64;
+
+    return 0;
+}
+
+ssize_t cpu_get_note_size(int class, int machine, int nr_cpus)
+{
+    size_t note_size = 0;
+
+    if (class == ELFCLASS64) {
+        note_size = LOONGARCH_PRSTATUS_NOTE_SIZE + LOONGARCH_PRFPREG_NOTE_SIZE;
+    }
+
+    return note_size * nr_cpus;
+}

target/loongarch/cpu.c

@@ -768,6 +768,7 @@ static const TCGCPUOps loongarch_tcg_ops = {
 #include "hw/core/sysemu-cpu-ops.h"
 
 static const struct SysemuCPUOps loongarch_sysemu_ops = {
+    .write_elf64_note = loongarch_cpu_write_elf64_note,
     .get_phys_page_debug = loongarch_cpu_get_phys_page_debug,
 };
 

target/loongarch/internals.h

@@ -72,5 +72,7 @@ void write_fcc(CPULoongArchState *env, uint64_t val);
 int loongarch_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n);
 int loongarch_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n);
 void loongarch_cpu_register_gdb_regs_for_features(CPUState *cs);
+int loongarch_cpu_write_elf64_note(WriteCoreDumpFunction f, CPUState *cpu,
+                                   int cpuid, DumpState *s);
 
 #endif

target/loongarch/meson.build

@@ -8,6 +8,7 @@ loongarch_ss.add(files(
 
 loongarch_system_ss = ss.source_set()
 loongarch_system_ss.add(files(
+  'arch_dump.c',
   'cpu_helper.c',
   'loongarch-qmp-cmds.c',
   'machine.c',