hw/mips: Add a bootloader helper

Add a bootloader helper to generate simple bootloaders for kernel.
It can help us reduce inline hex hack and also keep MIPS release 6
compatibility easier.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210127065424.114125-2-jiaxun.yang@flygoat.com>
[PMD: Restricted bl_reg enum to C source,
      inverted bl_gen_write() args,
      added license in hw/mips/bootloader.h]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

2 files changed, 201 insertions, 1 deletions

diff --git a/hw/mips/bootloader.c b/hw/mips/bootloader.c
new file mode 100644
index 0000000..6ec8314
--- /dev/null
+++ b/hw/mips/bootloader.c
@@ -0,0 +1,200 @@
+/*
+ * Utility for QEMU MIPS to generate it's simple bootloader
+ *
+ * Instructions used here are carefully selected to keep compatibility with
+ * MIPS Release 6.
+ *
+ * Copyright (C) 2020 Jiaxun Yang <jiaxun.yang@flygoat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/bitops.h"
+#include "cpu.h"
+#include "hw/mips/bootloader.h"
+
+typedef enum bl_reg {
+    BL_REG_ZERO = 0,
+    BL_REG_AT = 1,
+    BL_REG_V0 = 2,
+    BL_REG_V1 = 3,
+    BL_REG_A0 = 4,
+    BL_REG_A1 = 5,
+    BL_REG_A2 = 6,
+    BL_REG_A3 = 7,
+    BL_REG_T0 = 8,
+    BL_REG_T1 = 9,
+    BL_REG_T2 = 10,
+    BL_REG_T3 = 11,
+    BL_REG_T4 = 12,
+    BL_REG_T5 = 13,
+    BL_REG_T6 = 14,
+    BL_REG_T7 = 15,
+    BL_REG_S0 = 16,
+    BL_REG_S1 = 17,
+    BL_REG_S2 = 18,
+    BL_REG_S3 = 19,
+    BL_REG_S4 = 20,
+    BL_REG_S5 = 21,
+    BL_REG_S6 = 22,
+    BL_REG_S7 = 23,
+    BL_REG_T8 = 24,
+    BL_REG_T9 = 25,
+    BL_REG_K0 = 26,
+    BL_REG_K1 = 27,
+    BL_REG_GP = 28,
+    BL_REG_SP = 29,
+    BL_REG_FP = 30,
+    BL_REG_RA = 31,
+} bl_reg;
+
+static bool bootcpu_supports_isa(uint64_t isa_mask)
+{
+    return cpu_supports_isa(&MIPS_CPU(first_cpu)->env, isa_mask);
+}
+
+/* Base types */
+static void bl_gen_nop(uint32_t **p)
+{
+    stl_p(*p, 0);
+    *p = *p + 1;
+}
+
+static void bl_gen_r_type(uint32_t **p, uint8_t opcode,
+                          bl_reg rs, bl_reg rt, bl_reg rd,
+                          uint8_t shift, uint8_t funct)
+{
+    uint32_t insn = 0;
+
+    insn = deposit32(insn, 26, 6, opcode);
+    insn = deposit32(insn, 21, 5, rs);
+    insn = deposit32(insn, 16, 5, rt);
+    insn = deposit32(insn, 11, 5, rd);
+    insn = deposit32(insn, 6, 5, shift);
+    insn = deposit32(insn, 0, 6, funct);
+
+    stl_p(*p, insn);
+    *p = *p + 1;
+}
+
+static void bl_gen_i_type(uint32_t **p, uint8_t opcode,
+                          bl_reg rs, bl_reg rt, uint16_t imm)
+{
+    uint32_t insn = 0;
+
+    insn = deposit32(insn, 26, 6, opcode);
+    insn = deposit32(insn, 21, 5, rs);
+    insn = deposit32(insn, 16, 5, rt);
+    insn = deposit32(insn, 0, 16, imm);
+
+    stl_p(*p, insn);
+    *p = *p + 1;
+}
+
+/* Single instructions */
+static void bl_gen_dsll(uint32_t **p, bl_reg rd, bl_reg rt, uint8_t sa)
+{
+    if (bootcpu_supports_isa(ISA_MIPS3)) {
+        bl_gen_r_type(p, 0, 0, rt, rd, sa, 0x38);
+    } else {
+        g_assert_not_reached(); /* unsupported */
+    }
+}
+
+static void bl_gen_jalr(uint32_t **p, bl_reg rs)
+{
+    bl_gen_r_type(p, 0, rs, 0, BL_REG_RA, 0, 0x09);
+}
+
+static void bl_gen_lui(uint32_t **p, bl_reg rt, uint16_t imm)
+{
+    /* R6: It's a alias of AUI with RS = 0 */
+    bl_gen_i_type(p, 0x0f, 0, rt, imm);
+}
+
+static void bl_gen_ori(uint32_t **p, bl_reg rt, bl_reg rs, uint16_t imm)
+{
+    bl_gen_i_type(p, 0x0d, rs, rt, imm);
+}
+
+static void bl_gen_sw(uint32_t **p, bl_reg rt, uint8_t base, uint16_t offset)
+{
+    bl_gen_i_type(p, 0x2b, base, rt, offset);
+}
+
+static void bl_gen_sd(uint32_t **p, bl_reg rt, uint8_t base, uint16_t offset)
+{
+    if (bootcpu_supports_isa(ISA_MIPS3)) {
+        bl_gen_i_type(p, 0x3f, base, rt, offset);
+    } else {
+        g_assert_not_reached(); /* unsupported */
+    }
+}
+
+/* Pseudo instructions */
+static void bl_gen_li(uint32_t **p, bl_reg rt, uint32_t imm)
+{
+    bl_gen_lui(p, rt, extract32(imm, 16, 16));
+    bl_gen_ori(p, rt, rt, extract32(imm, 0, 16));
+}
+
+static void bl_gen_dli(uint32_t **p, bl_reg rt, uint64_t imm)
+{
+    bl_gen_li(p, rt, extract64(imm, 32, 32));
+    bl_gen_dsll(p, rt, rt, 16);
+    bl_gen_ori(p, rt, rt, extract64(imm, 16, 16));
+    bl_gen_dsll(p, rt, rt, 16);
+    bl_gen_ori(p, rt, rt, extract64(imm, 0, 16));
+}
+
+static void bl_gen_load_ulong(uint32_t **p, bl_reg rt, target_ulong imm)
+{
+    if (bootcpu_supports_isa(ISA_MIPS3)) {
+        bl_gen_dli(p, rt, imm); /* 64bit */
+    } else {
+        bl_gen_li(p, rt, imm); /* 32bit */
+    }
+}
+
+/* Helpers */
+void bl_gen_jump_to(uint32_t **p, target_ulong jump_addr)
+{
+    bl_gen_load_ulong(p, BL_REG_T9, jump_addr);
+    bl_gen_jalr(p, BL_REG_T9);
+    bl_gen_nop(p); /* delay slot */
+}
+
+void bl_gen_jump_kernel(uint32_t **p, target_ulong sp, target_ulong a0,
+                        target_ulong a1, target_ulong a2, target_ulong a3,
+                        target_ulong kernel_addr)
+{
+    bl_gen_load_ulong(p, BL_REG_SP, sp);
+    bl_gen_load_ulong(p, BL_REG_A0, a0);
+    bl_gen_load_ulong(p, BL_REG_A1, a1);
+    bl_gen_load_ulong(p, BL_REG_A2, a2);
+    bl_gen_load_ulong(p, BL_REG_A3, a3);
+
+    bl_gen_jump_to(p, kernel_addr);
+}
+
+void bl_gen_write_ulong(uint32_t **p, target_ulong addr, target_ulong val)
+{
+    bl_gen_load_ulong(p, BL_REG_K0, val);
+    bl_gen_load_ulong(p, BL_REG_K1, addr);
+    bl_gen_sd(p, BL_REG_K0, BL_REG_K1, 0x0);
+}
+
+void bl_gen_write_u32(uint32_t **p, target_ulong addr, uint32_t val)
+{
+    bl_gen_li(p, BL_REG_K0, val);
+    bl_gen_load_ulong(p, BL_REG_K1, addr);
+    bl_gen_sw(p, BL_REG_K0, BL_REG_K1, 0x0);
+}
+
+void bl_gen_write_u64(uint32_t **p, target_ulong addr, uint64_t val)
+{
+    bl_gen_dli(p, BL_REG_K0, val);
+    bl_gen_load_ulong(p, BL_REG_K1, addr);
+    bl_gen_sd(p, BL_REG_K0, BL_REG_K1, 0x0);
+}
diff --git a/hw/mips/meson.build b/hw/mips/meson.build
index ee19cc2..1195716 100644
--- a/hw/mips/meson.build
+++ b/hw/mips/meson.build
@@ -1,5 +1,5 @@
 mips_ss = ss.source_set()
-mips_ss.add(files('mips_int.c'))
+mips_ss.add(files('bootloader.c', 'mips_int.c'))
 mips_ss.add(when: 'CONFIG_FW_CFG_MIPS', if_true: files('fw_cfg.c'))
 mips_ss.add(when: 'CONFIG_FULOONG', if_true: files('fuloong2e.c'))
 mips_ss.add(when: 'CONFIG_LOONGSON3V', if_true: files('loongson3_bootp.c', 'loongson3_virt.c'))