target-riscv: 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 RISC-V only contain prstatus elf notes.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Mingwang Li <limingwang@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Message-id: 20210201124458.1248-2-jiangyifei@huawei.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/arch_dump.c

@@ -0,0 +1,202 @@
+/* Support for writing ELF notes for RISC-V architectures
+ *
+ * Copyright (C) 2021 Huawei Technologies Co., Ltd
+ *
+ * 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"
+
+/* struct user_regs_struct from arch/riscv/include/uapi/asm/ptrace.h */
+struct riscv64_user_regs {
+    uint64_t pc;
+    uint64_t regs[31];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct riscv64_user_regs) != 256);
+
+/* struct elf_prstatus from include/linux/elfcore.h */
+struct riscv64_elf_prstatus {
+    char pad1[32]; /* 32 == offsetof(struct elf_prstatus, pr_pid) */
+    uint32_t pr_pid;
+    char pad2[76]; /* 76 == offsetof(struct elf_prstatus, pr_reg) -
+                            offsetof(struct elf_prstatus, pr_ppid) */
+    struct riscv64_user_regs pr_reg;
+    char pad3[8];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct riscv64_elf_prstatus) != 376);
+
+struct riscv64_note {
+    Elf64_Nhdr hdr;
+    char name[8]; /* align_up(sizeof("CORE"), 4) */
+    struct riscv64_elf_prstatus prstatus;
+} QEMU_PACKED;
+
+#define RISCV64_NOTE_HEADER_SIZE offsetof(struct riscv64_note, prstatus)
+#define RISCV64_PRSTATUS_NOTE_SIZE \
+            (RISCV64_NOTE_HEADER_SIZE + sizeof(struct riscv64_elf_prstatus))
+
+static void riscv64_note_init(struct riscv64_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);
+}
+
+int riscv_cpu_write_elf64_note(WriteCoreDumpFunction f, CPUState *cs,
+                               int cpuid, void *opaque)
+{
+    struct riscv64_note note;
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    CPURISCVState *env = &cpu->env;
+    DumpState *s = opaque;
+    int ret, i = 0;
+    const char name[] = "CORE";
+
+    riscv64_note_init(&note, s, name, sizeof(name),
+                      NT_PRSTATUS, sizeof(note.prstatus));
+
+    note.prstatus.pr_pid = cpu_to_dump32(s, cpuid);
+
+    note.prstatus.pr_reg.pc = cpu_to_dump64(s, env->pc);
+
+    for (i = 0; i < 31; i++) {
+        note.prstatus.pr_reg.regs[i] = cpu_to_dump64(s, env->gpr[i + 1]);
+    }
+
+    ret = f(&note, RISCV64_PRSTATUS_NOTE_SIZE, s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    return ret;
+}
+
+struct riscv32_user_regs {
+    uint32_t pc;
+    uint32_t regs[31];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct riscv32_user_regs) != 128);
+
+struct riscv32_elf_prstatus {
+    char pad1[24]; /* 24 == offsetof(struct elf_prstatus, pr_pid) */
+    uint32_t pr_pid;
+    char pad2[44]; /* 44 == offsetof(struct elf_prstatus, pr_reg) -
+                            offsetof(struct elf_prstatus, pr_ppid) */
+    struct riscv32_user_regs pr_reg;
+    char pad3[4];
+} QEMU_PACKED;
+
+QEMU_BUILD_BUG_ON(sizeof(struct riscv32_elf_prstatus) != 204);
+
+struct riscv32_note {
+    Elf32_Nhdr hdr;
+    char name[8]; /* align_up(sizeof("CORE"), 4) */
+    struct riscv32_elf_prstatus prstatus;
+} QEMU_PACKED;
+
+#define RISCV32_NOTE_HEADER_SIZE offsetof(struct riscv32_note, prstatus)
+#define RISCV32_PRSTATUS_NOTE_SIZE \
+            (RISCV32_NOTE_HEADER_SIZE + sizeof(struct riscv32_elf_prstatus))
+
+static void riscv32_note_init(struct riscv32_note *note, DumpState *s,
+                              const char *name, Elf32_Word namesz,
+                              Elf32_Word type, Elf32_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);
+}
+
+int riscv_cpu_write_elf32_note(WriteCoreDumpFunction f, CPUState *cs,
+                               int cpuid, void *opaque)
+{
+    struct riscv32_note note;
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    CPURISCVState *env = &cpu->env;
+    DumpState *s = opaque;
+    int ret, i;
+    const char name[] = "CORE";
+
+    riscv32_note_init(&note, s, name, sizeof(name),
+                      NT_PRSTATUS, sizeof(note.prstatus));
+
+    note.prstatus.pr_pid = cpu_to_dump32(s, cpuid);
+
+    note.prstatus.pr_reg.pc = cpu_to_dump32(s, env->pc);
+
+    for (i = 0; i < 31; i++) {
+        note.prstatus.pr_reg.regs[i] = cpu_to_dump32(s, env->gpr[i + 1]);
+    }
+
+    ret = f(&note, RISCV32_PRSTATUS_NOTE_SIZE, s);
+    if (ret < 0) {
+        return -1;
+    }
+
+    return ret;
+}
+
+int cpu_get_dump_info(ArchDumpInfo *info,
+                      const GuestPhysBlockList *guest_phys_blocks)
+{
+    RISCVCPU *cpu;
+    CPURISCVState *env;
+
+    if (first_cpu == NULL) {
+        return -1;
+    }
+    cpu = RISCV_CPU(first_cpu);
+    env = &cpu->env;
+
+    info->d_machine = EM_RISCV;
+
+#if defined(TARGET_RISCV64)
+    info->d_class = ELFCLASS64;
+#else
+    info->d_class = ELFCLASS32;
+#endif
+
+    info->d_endian = (env->mstatus & MSTATUS_UBE) != 0
+                     ? ELFDATA2MSB : ELFDATA2LSB;
+
+    return 0;
+}
+
+ssize_t cpu_get_note_size(int class, int machine, int nr_cpus)
+{
+    size_t note_size;
+
+    if (class == ELFCLASS64) {
+        note_size = RISCV64_PRSTATUS_NOTE_SIZE;
+    } else {
+        note_size = RISCV32_PRSTATUS_NOTE_SIZE;
+    }
+
+    return note_size * nr_cpus;
+}

target/riscv/cpu.c

@@ -624,6 +624,8 @@ static void riscv_cpu_class_init(ObjectClass *c, void *data)
     cc->get_phys_page_debug = riscv_cpu_get_phys_page_debug;
     /* For now, mark unmigratable: */
     cc->vmsd = &vmstate_riscv_cpu;
+    cc->write_elf64_note = riscv_cpu_write_elf64_note;
+    cc->write_elf32_note = riscv_cpu_write_elf32_note;
 #endif
     cc->gdb_arch_name = riscv_gdb_arch_name;
     cc->gdb_get_dynamic_xml = riscv_gdb_get_dynamic_xml;

target/riscv/cpu.h

@@ -323,6 +323,10 @@ extern const char * const riscv_intr_names[];
 
 const char *riscv_cpu_get_trap_name(target_ulong cause, bool async);
 void riscv_cpu_do_interrupt(CPUState *cpu);
+int riscv_cpu_write_elf64_note(WriteCoreDumpFunction f, CPUState *cs,
+                               int cpuid, void *opaque);
+int riscv_cpu_write_elf32_note(WriteCoreDumpFunction f, CPUState *cs,
+                               int cpuid, void *opaque);
 int riscv_cpu_gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
 int riscv_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
 bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request);

target/riscv/cpu_bits.h

@@ -368,6 +368,7 @@
 #define MSTATUS_MIE         0x00000008
 #define MSTATUS_UPIE        0x00000010
 #define MSTATUS_SPIE        0x00000020
+#define MSTATUS_UBE         0x00000040
 #define MSTATUS_MPIE        0x00000080
 #define MSTATUS_SPP         0x00000100
 #define MSTATUS_MPP         0x00001800

target/riscv/meson.build

@@ -26,6 +26,7 @@ riscv_ss.add(files(
 
 riscv_softmmu_ss = ss.source_set()
 riscv_softmmu_ss.add(files(
+  'arch_dump.c',
   'pmp.c',
   'monitor.c',
   'machine.c'