[PATCH v2 2/3] tests: add unit tests for ISV=0 emulation library

[Lucas Amaral <lucaaamaral@gmail.com>]

Add test-arm-emulate with 19 test cases covering the arm_emul_ops
callback interface using a mock environment.  Encodings and expected
values verified against ARM architecture ground truth.

Signed-off-by: Lucas Amaral <lucaaamaral@gmail.com>
---
 tests/unit/meson.build        |   1 +
 tests/unit/test-arm-emulate.c | 540 ++++++++++++++++++++++++++++++++++
 2 files changed, 541 insertions(+)
 create mode 100644 tests/unit/test-arm-emulate.c

diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 41e8b06..27a515b 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -157,6 +157,7 @@ if have_system
     }
   endif
   tests += {'test-qdev': [qom, hwcore]}
+  tests += {'test-arm-emulate': [arm_emulate_test]}
 endif
 
 if have_ga and host_os == 'linux'
diff --git a/tests/unit/test-arm-emulate.c b/tests/unit/test-arm-emulate.c
new file mode 100644
index 0000000..5ab7f04
--- /dev/null
+++ b/tests/unit/test-arm-emulate.c
@@ -0,0 +1,540 @@
+/*
+ * Unit tests for AArch64 ISV=0 instruction emulation library
+ *
+ * Copyright (c) 2026 Lucas Amaral <lucaaamaral@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "arm_emulate.h"
+
+/* Mock environment: GPR, FPR, and flat memory */
+
+typedef struct MockEnv {
+    uint64_t gpr[32];          /* X0-X30, X31=SP */
+    uint8_t  fpr[32][16];      /* V0-V31, 128 bits each */
+    uint8_t  mem[0x1000];      /* 4 KiB flat address space */
+    bool     mem_fail;         /* if true, memory ops return -1 */
+} MockEnv;
+
+static MockEnv *env_from_cpu(CPUState *cpu)
+{
+    return (MockEnv *)cpu;
+}
+
+static uint64_t mock_read_gpr(CPUState *cpu, int reg)
+{
+    return env_from_cpu(cpu)->gpr[reg];
+}
+
+static void mock_write_gpr(CPUState *cpu, int reg, uint64_t val)
+{
+    env_from_cpu(cpu)->gpr[reg] = val;
+}
+
+static void mock_read_fpreg(CPUState *cpu, int reg, void *buf, int size)
+{
+    memcpy(buf, env_from_cpu(cpu)->fpr[reg], size);
+}
+
+static void mock_write_fpreg(CPUState *cpu, int reg, const void *buf, int size)
+{
+    MockEnv *env = env_from_cpu(cpu);
+    memset(env->fpr[reg], 0, 16);
+    memcpy(env->fpr[reg], buf, size);
+}
+
+static int mock_read_mem(CPUState *cpu, uint64_t va, void *buf, int size)
+{
+    MockEnv *env = env_from_cpu(cpu);
+    if (env->mem_fail || va + size > sizeof(env->mem)) {
+        return -1;
+    }
+    memcpy(buf, env->mem + va, size);
+    return 0;
+}
+
+static int mock_write_mem(CPUState *cpu, uint64_t va, const void *buf, int size)
+{
+    MockEnv *env = env_from_cpu(cpu);
+    if (env->mem_fail || va + size > sizeof(env->mem)) {
+        return -1;
+    }
+    memcpy(env->mem + va, buf, size);
+    return 0;
+}
+
+static const struct arm_emul_ops mock_ops = {
+    .read_gpr    = mock_read_gpr,
+    .write_gpr   = mock_write_gpr,
+    .read_fpreg  = mock_read_fpreg,
+    .write_fpreg = mock_write_fpreg,
+    .read_mem    = mock_read_mem,
+    .write_mem   = mock_write_mem,
+};
+
+/* Helper: reset mock environment */
+static MockEnv *fresh_env(MockEnv *env)
+{
+    memset(env, 0, sizeof(*env));
+    return env;
+}
+
+/* Helper: call arm_emul_insn with the mock environment */
+static ArmEmulResult emul(MockEnv *env, uint32_t insn)
+{
+    return arm_emul_insn((CPUState *)env, &mock_ops, insn);
+}
+
+/* Helper: write a uint64_t to mock memory at a given VA */
+static void mem_write64(MockEnv *env, uint64_t va, uint64_t val)
+{
+    memcpy(env->mem + va, &val, 8);
+}
+
+/* Helper: read a uint64_t from mock memory */
+static uint64_t mem_read64(MockEnv *env, uint64_t va)
+{
+    uint64_t val = 0;
+    memcpy(&val, env->mem + va, 8);
+    return val;
+}
+
+/* Helper: read a uint32_t from mock memory */
+static uint32_t mem_read32(MockEnv *env, uint64_t va)
+{
+    uint32_t val = 0;
+    memcpy(&val, env->mem + va, 4);
+    return val;
+}
+
+/* STP / LDP (64-bit store/load pair, signed offset) */
+
+/*
+ * STP X0, X1, [X2]
+ *   10 101 0 010 0 0000000 00001 00010 00000
+ *   = 0xA9000440
+ */
+static void test_stp_offset(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 0xDEADBEEF;
+    env.gpr[1] = 0xCAFEBABE;
+    env.gpr[2] = 0x100;  /* base address */
+
+    g_assert_cmpint(emul(&env, 0xA9000440), ==, ARM_EMUL_OK);
+
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 0xDEADBEEF);
+    g_assert_cmphex(mem_read64(&env, 0x108), ==, 0xCAFEBABE);
+    /* No writeback — base unchanged */
+    g_assert_cmphex(env.gpr[2], ==, 0x100);
+}
+
+/*
+ * LDP X3, X4, [X5]
+ *   10 101 0 010 1 0000000 00100 00101 00011
+ *   = 0xA94010A3
+ */
+static void test_ldp_offset(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[5] = 0x200;
+    mem_write64(&env, 0x200, 0x1111111111111111ULL);
+    mem_write64(&env, 0x208, 0x2222222222222222ULL);
+
+    g_assert_cmpint(emul(&env, 0xA94010A3), ==, ARM_EMUL_OK);
+
+    g_assert_cmphex(env.gpr[3], ==, 0x1111111111111111ULL);
+    g_assert_cmphex(env.gpr[4], ==, 0x2222222222222222ULL);
+}
+
+/* STP pre-indexed (writeback) */
+
+/*
+ * STP X0, X1, [X2, #16]!
+ *   10 101 0 011 0 0000010 00001 00010 00000
+ *   = 0xA9810440
+ *   imm7=+2, scaled by 8 = offset +16
+ */
+static void test_stp_preindex(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 0xAAAA;
+    env.gpr[1] = 0xBBBB;
+    env.gpr[2] = 0x100;
+
+    g_assert_cmpint(emul(&env, 0xA9810440), ==, ARM_EMUL_OK);
+
+    /* Data stored at base+16 = 0x110 */
+    g_assert_cmphex(mem_read64(&env, 0x110), ==, 0xAAAA);
+    g_assert_cmphex(mem_read64(&env, 0x118), ==, 0xBBBB);
+    /* Writeback: base updated to base+16 */
+    g_assert_cmphex(env.gpr[2], ==, 0x110);
+}
+
+/* STR / LDR unsigned offset (64-bit) */
+
+/*
+ * STR X0, [X1]
+ *   11 111 0 01 00 000000000000 00001 00000
+ *   = 0xF9000020
+ */
+static void test_str_uoffset(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 0x42;
+    env.gpr[1] = 0x80;
+
+    g_assert_cmpint(emul(&env, 0xF9000020), ==, ARM_EMUL_OK);
+    g_assert_cmphex(mem_read64(&env, 0x80), ==, 0x42);
+}
+
+/*
+ * LDR X2, [X1]
+ *   11 111 0 01 01 000000000000 00001 00010
+ *   = 0xF9400022
+ */
+static void test_ldr_uoffset(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x80;
+    mem_write64(&env, 0x80, 0xFEDCBA9876543210ULL);
+
+    g_assert_cmpint(emul(&env, 0xF9400022), ==, ARM_EMUL_OK);
+    g_assert_cmphex(env.gpr[2], ==, 0xFEDCBA9876543210ULL);
+}
+
+/* LDRB zero-extend / LDRSB sign-extend */
+
+/*
+ * LDRB W2, [X1]  (zero-extend byte to 32-bit)
+ *   00 111 0 01 01 000000000000 00001 00010
+ *   = 0x39400022
+ */
+static void test_ldrb_zero_extend(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x80;
+    env.mem[0x80] = 0xFF;
+
+    g_assert_cmpint(emul(&env, 0x39400022), ==, ARM_EMUL_OK);
+    g_assert_cmphex(env.gpr[2], ==, 0xFF);
+}
+
+/*
+ * LDRSB X2, [X1]  (sign-extend byte to 64-bit)
+ *   00 111 0 01 10 000000000000 00001 00010
+ *   = 0x39800022
+ */
+static void test_ldrsb_sign_extend(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x80;
+    env.mem[0x80] = 0x80;  /* -128 as signed byte */
+
+    g_assert_cmpint(emul(&env, 0x39800022), ==, ARM_EMUL_OK);
+    g_assert_cmphex(env.gpr[2], ==, 0xFFFFFFFFFFFFFF80ULL);
+}
+
+/* XZR -- register 31 reads as zero for GPR data */
+
+/*
+ * STR XZR, [X1]  (store zero register)
+ *   11 111 0 01 00 000000000000 00001 11111
+ *   = 0xF900003F
+ */
+static void test_xzr_reads_zero(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[31] = 0x9999;  /* SP value — should NOT be stored */
+    env.gpr[1] = 0x80;
+    mem_write64(&env, 0x80, 0xFFFF);  /* pre-fill to verify overwrite */
+
+    g_assert_cmpint(emul(&env, 0xF900003F), ==, ARM_EMUL_OK);
+    /* XZR is zero, not SP */
+    g_assert_cmphex(mem_read64(&env, 0x80), ==, 0);
+}
+
+/* Atomic -- LDADD */
+
+/*
+ * LDADD X0, X1, [X2]
+ *   11 111 0 00 00 1 00000 0000 00 00010 00001
+ *   = 0xF8200041
+ *   sz=3, a=0, r=0, rs=0, opc=0000 (ADD), rn=2, rt=1
+ */
+static void test_ldadd(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 5;       /* operand (Rs) */
+    env.gpr[2] = 0x100;   /* base address */
+    mem_write64(&env, 0x100, 10);  /* old value */
+
+    g_assert_cmpint(emul(&env, 0xF8200041), ==, ARM_EMUL_OK);
+
+    /* Rt gets old value */
+    g_assert_cmphex(env.gpr[1], ==, 10);
+    /* Memory gets old + operand */
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 15);
+}
+
+/* SWP */
+
+/*
+ * SWP X0, X1, [X2]
+ *   11 111 0 00 00 1 00000 1000 00 00010 00001
+ *   = 0xF8208041
+ */
+static void test_swp(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 42;      /* new value (Rs) */
+    env.gpr[2] = 0x100;   /* base address */
+    mem_write64(&env, 0x100, 99);  /* old value */
+
+    g_assert_cmpint(emul(&env, 0xF8208041), ==, ARM_EMUL_OK);
+
+    /* Rt gets old value */
+    g_assert_cmphex(env.gpr[1], ==, 99);
+    /* Memory gets new value */
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 42);
+}
+
+/* CAS (compare-and-swap, 64-bit) */
+
+/*
+ * CAS X0, X2, [X4]
+ *   11 001000 1 0 1 00000 0 11111 00100 00010
+ *   = 0xC8A07C82
+ *   sz=3, a=0, r=0, rs=0 (compare), rt=2 (new), rn=4 (base)
+ */
+static void test_cas_match(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 100;     /* Rs: compare value */
+    env.gpr[2] = 200;     /* Rt: new value */
+    env.gpr[4] = 0x100;   /* Rn: base address */
+    mem_write64(&env, 0x100, 100);  /* memory == compare, swap occurs */
+
+    g_assert_cmpint(emul(&env, 0xC8A07C82), ==, ARM_EMUL_OK);
+
+    /* Rs gets old memory value */
+    g_assert_cmphex(env.gpr[0], ==, 100);
+    /* Memory updated to new value */
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 200);
+}
+
+/* CAS with no match — memory unchanged */
+static void test_cas_nomatch(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 100;     /* compare */
+    env.gpr[2] = 200;     /* new */
+    env.gpr[4] = 0x100;
+    mem_write64(&env, 0x100, 999);  /* memory != compare, no swap */
+
+    g_assert_cmpint(emul(&env, 0xC8A07C82), ==, ARM_EMUL_OK);
+
+    g_assert_cmphex(env.gpr[0], ==, 999);  /* Rs gets old value */
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 999);  /* unchanged */
+}
+
+/* CASP (pair compare-and-swap) */
+
+/*
+ * CASP X0, X1, X2, X3, [X4]  (64-bit pair)
+ *   01 001000 0 0 1 00000 0 11111 00100 00010
+ *   = 0x48207C82
+ */
+static void test_casp_match(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[0] = 0xAA;  env.gpr[1] = 0xBB;  /* Rs pair: compare */
+    env.gpr[2] = 0xCC;  env.gpr[3] = 0xDD;  /* Rt pair: new */
+    env.gpr[4] = 0x100;
+    mem_write64(&env, 0x100, 0xAA);
+    mem_write64(&env, 0x108, 0xBB);
+
+    g_assert_cmpint(emul(&env, 0x48207C82), ==, ARM_EMUL_OK);
+
+    g_assert_cmphex(mem_read64(&env, 0x100), ==, 0xCC);
+    g_assert_cmphex(mem_read64(&env, 0x108), ==, 0xDD);
+}
+
+/* CASP with odd register -- validation rejects */
+
+/*
+ * CASP with Rs=X1 (odd) -- trans_CASP returns false
+ *   01 001000 0 0 1 00001 0 11111 00100 00010
+ *   = 0x48217C82
+ */
+static void test_casp_odd_register(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[4] = 0x100;
+
+    /* Odd Rs -- decoder returns false -- ARM_EMUL_UNHANDLED */
+    g_assert_cmpint(emul(&env, 0x48217C82), ==, ARM_EMUL_UNHANDLED);
+}
+
+/* Unrecognized instruction -- ARM_EMUL_UNHANDLED */
+
+static void test_unhandled(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    /* B #0 = 0x14000000 — a branch, not a load/store */
+    g_assert_cmpint(emul(&env, 0x14000000), ==, ARM_EMUL_UNHANDLED);
+}
+
+/* Memory error -- ARM_EMUL_ERR_MEM */
+
+static void test_mem_error(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x80;
+    env.mem_fail = true;
+
+    /* LDR X2, [X1] — memory read will fail */
+    g_assert_cmpint(emul(&env, 0xF9400022), ==, ARM_EMUL_ERR_MEM);
+}
+
+/* PRFM (prefetch) -- NOP, returns OK */
+
+/*
+ * PRFM #0, [X1]  (unsigned offset, imm=0)
+ *   11 111 0 01 10 000000000000 00001 00000
+ *   = 0xF9800020
+ */
+static void test_prfm_nop(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x80;
+
+    g_assert_cmpint(emul(&env, 0xF9800020), ==, ARM_EMUL_OK);
+    /* No state change — it's a NOP */
+}
+
+/* SIMD/FP store/load pair */
+
+/*
+ * STP S0, S1, [X2]  (32-bit FP pair, signed offset, imm=0)
+ *   00 101 1 010 0 0000000 00001 00010 00000
+ *   = 0x2D000440
+ */
+static void test_stp_fp(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    uint32_t f0 = 0x3F800000;  /* 1.0f */
+    uint32_t f1 = 0x40000000;  /* 2.0f */
+    memcpy(env.fpr[0], &f0, 4);
+    memcpy(env.fpr[1], &f1, 4);
+    env.gpr[2] = 0x200;
+
+    g_assert_cmpint(emul(&env, 0x2D000440), ==, ARM_EMUL_OK);
+
+    g_assert_cmphex(mem_read32(&env, 0x200), ==, 0x3F800000);
+    g_assert_cmphex(mem_read32(&env, 0x204), ==, 0x40000000);
+}
+
+/* LDR post-indexed (writeback after load) */
+
+/*
+ * LDR X3, [X1], #8  (post-indexed, imm=+8)
+ *   11 111 0 00 01 0 000001000 01 00001 00011
+ *   = 0xF8408423
+ *   sz=3, opc=01, imm9=+8, type=01 (post-index), rn=1, rt=3
+ */
+static void test_ldr_postindex(void)
+{
+    MockEnv env;
+    fresh_env(&env);
+
+    env.gpr[1] = 0x100;
+    mem_write64(&env, 0x100, 0x55AA55AA55AA55AAULL);
+
+    g_assert_cmpint(emul(&env, 0xF8408423), ==, ARM_EMUL_OK);
+
+    /* Load from original base */
+    g_assert_cmphex(env.gpr[3], ==, 0x55AA55AA55AA55AAULL);
+    /* Writeback: base += 8 */
+    g_assert_cmphex(env.gpr[1], ==, 0x108);
+}
+
+/* Entry point */
+
+int main(int argc, char **argv)
+{
+    g_test_init(&argc, &argv, NULL);
+
+    /* Load/store pair */
+    g_test_add_func("/arm-emulate/stp-offset", test_stp_offset);
+    g_test_add_func("/arm-emulate/ldp-offset", test_ldp_offset);
+    g_test_add_func("/arm-emulate/stp-preindex", test_stp_preindex);
+    g_test_add_func("/arm-emulate/stp-fp", test_stp_fp);
+
+    /* Load/store single */
+    g_test_add_func("/arm-emulate/str-uoffset", test_str_uoffset);
+    g_test_add_func("/arm-emulate/ldr-uoffset", test_ldr_uoffset);
+    g_test_add_func("/arm-emulate/ldr-postindex", test_ldr_postindex);
+    g_test_add_func("/arm-emulate/ldrb-zero-extend", test_ldrb_zero_extend);
+    g_test_add_func("/arm-emulate/ldrsb-sign-extend", test_ldrsb_sign_extend);
+
+    /* XZR */
+    g_test_add_func("/arm-emulate/xzr-reads-zero", test_xzr_reads_zero);
+
+    /* Atomics */
+    g_test_add_func("/arm-emulate/ldadd", test_ldadd);
+    g_test_add_func("/arm-emulate/swp", test_swp);
+
+    /* Compare-and-swap */
+    g_test_add_func("/arm-emulate/cas-match", test_cas_match);
+    g_test_add_func("/arm-emulate/cas-nomatch", test_cas_nomatch);
+    g_test_add_func("/arm-emulate/casp-match", test_casp_match);
+    g_test_add_func("/arm-emulate/casp-odd-register", test_casp_odd_register);
+
+    /* NOP */
+    g_test_add_func("/arm-emulate/prfm-nop", test_prfm_nop);
+
+    /* Error handling */
+    g_test_add_func("/arm-emulate/unhandled", test_unhandled);
+    g_test_add_func("/arm-emulate/mem-error", test_mem_error);
+
+    return g_test_run();
+}
-- 
2.52.0