[PATCH 74/82] linux-user/aarch64: Implement map_shadow_stack syscall

[Richard Henderson <richard.henderson@linaro.org>]

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/syscall.c | 59 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index dfe114ceb3..0a7ce7a262 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6356,6 +6356,12 @@ abi_long do_arch_prctl(CPUX86State *env, int code, abi_ulong addr)
 # define PR_SET_SHADOW_STACK_STATUS  75
 # define PR_LOCK_SHADOW_STACK_STATUS 76
 #endif
+#ifndef SHADOW_STACK_SET_TOKEN
+# define SHADOW_STACK_SET_TOKEN  (1u << 0)
+#endif
+#ifndef SHADOW_STACK_SET_MARKER
+# define SHADOW_STACK_SET_MARKER (1u << 1)
+#endif
 
 #include "target_prctl.h"
 
@@ -6571,6 +6577,54 @@ static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
     }
 }
 
+#ifdef TARGET_AARCH64
+static abi_long do_map_shadow_stack(CPUArchState *env, abi_ulong addr,
+                                    abi_ulong size, abi_int flags)
+{
+    ARMCPU *cpu = env_archcpu(env);
+    abi_ulong alloc_size;
+
+    if (!cpu_isar_feature(aa64_gcs, cpu)) {
+        return -TARGET_EOPNOTSUPP;
+    }
+    if (flags & ~(SHADOW_STACK_SET_TOKEN | SHADOW_STACK_SET_MARKER)) {
+        return -TARGET_EINVAL;
+    }
+    if (addr & ~TARGET_PAGE_MASK) {
+        return -TARGET_EINVAL;
+    }
+    if (size == 8 || !QEMU_IS_ALIGNED(size, 8)) {
+        return -TARGET_EINVAL;
+    }
+
+    alloc_size = TARGET_PAGE_ALIGN(size);
+    if (alloc_size < size) {
+        return -TARGET_EOVERFLOW;
+    }
+
+    mmap_lock();
+    addr = gcs_alloc(addr, alloc_size);
+    if (addr != -1) {
+        if (flags & SHADOW_STACK_SET_TOKEN) {
+            abi_ptr cap_ptr = addr + size - 8;
+            uint64_t cap_val;
+
+            if (flags & SHADOW_STACK_SET_MARKER) {
+                /* Leave an extra empty frame at top-of-stack. */
+                cap_ptr -= 8;
+            }
+            cap_val = (cap_ptr & TARGET_PAGE_MASK) | 1;
+            if (put_user_u64(cap_val, cap_ptr)) {
+                /* Allocation succeeded above. */
+                g_assert_not_reached();
+            }
+        }
+    }
+    mmap_unlock();
+    return get_errno(addr);
+}
+#endif
+
 #define NEW_STACK_SIZE 0x40000
 
 
@@ -13945,6 +13999,11 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
         return do_riscv_hwprobe(cpu_env, arg1, arg2, arg3, arg4, arg5);
 #endif
 
+#ifdef TARGET_AARCH64
+    case TARGET_NR_map_shadow_stack:
+        return do_map_shadow_stack(cpu_env, arg1, arg2, arg3);
+#endif
+
     default:
         qemu_log_mask(LOG_UNIMP, "Unsupported syscall: %d\n", num);
         return -TARGET_ENOSYS;
-- 
2.43.0