This is PR_GET_SHADOW_STACK_STATUS, PR_SET_SHADOW_STACK_STATUS,
and PR_LOCK_SHADOW_STACK_STATUS.
Reviewed-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
linux-user/aarch64/gcs-internal.h | 38 ++++++++++++
linux-user/aarch64/target_prctl.h | 96 +++++++++++++++++++++++++++++++
linux-user/qemu.h | 5 ++
linux-user/syscall.c | 29 ++++++++++
4 files changed, 168 insertions(+)
create mode 100644 linux-user/aarch64/gcs-internal.h
diff --git a/linux-user/aarch64/gcs-internal.h
b/linux-user/aarch64/gcs-internal.h
new file mode 100644
index 0000000000..e586c7e80e
--- /dev/null
+++ b/linux-user/aarch64/gcs-internal.h
@@ -0,0 +1,38 @@
+/*
+ * AArch64 gcs functions for linux-user
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef AARCH64_GCS_INTERNAL_H
+#define AARCH64_GCS_INTERNAL_H
+
+#ifndef PR_SHADOW_STACK_ENABLE
+# define PR_SHADOW_STACK_ENABLE (1U << 0)
+# define PR_SHADOW_STACK_WRITE (1U << 1)
+# define PR_SHADOW_STACK_PUSH (1U << 2)
+#endif
+
+static inline uint64_t gcs_get_el0_mode(CPUArchState *env)
+{
+ uint64_t cr = env->cp15.gcscr_el[0];
+ abi_ulong flags = 0;
+
+ flags |= cr & GCSCR_PCRSEL ? PR_SHADOW_STACK_ENABLE : 0;
+ flags |= cr & GCSCR_STREN ? PR_SHADOW_STACK_WRITE : 0;
+ flags |= cr & GCSCR_PUSHMEN ? PR_SHADOW_STACK_PUSH : 0;
+
+ return flags;
+}
+
+static inline void gcs_set_el0_mode(CPUArchState *env, uint64_t flags)
+{
+ uint64_t cr = GCSCRE0_NTR;
+
+ cr |= flags & PR_SHADOW_STACK_ENABLE ? GCSCR_RVCHKEN | GCSCR_PCRSEL : 0;
+ cr |= flags & PR_SHADOW_STACK_WRITE ? GCSCR_STREN : 0;
+ cr |= flags & PR_SHADOW_STACK_PUSH ? GCSCR_PUSHMEN : 0;
+
+ env->cp15.gcscr_el[0] = cr;
+}
+
+#endif
diff --git a/linux-user/aarch64/target_prctl.h
b/linux-user/aarch64/target_prctl.h
index ed75b9e4b5..621be5727f 100644
--- a/linux-user/aarch64/target_prctl.h
+++ b/linux-user/aarch64/target_prctl.h
@@ -6,8 +6,10 @@
#ifndef AARCH64_TARGET_PRCTL_H
#define AARCH64_TARGET_PRCTL_H
+#include "qemu/units.h"
#include "target/arm/cpu-features.h"
#include "mte_user_helper.h"
+#include "gcs-internal.h"
static abi_long do_prctl_sve_get_vl(CPUArchState *env)
{
@@ -206,4 +208,98 @@ static abi_long do_prctl_get_tagged_addr_ctrl(CPUArchState
*env)
}
#define do_prctl_get_tagged_addr_ctrl do_prctl_get_tagged_addr_ctrl
+static abi_long do_prctl_get_shadow_stack_status(CPUArchState *env,
+ abi_long arg2)
+{
+ ARMCPU *cpu = env_archcpu(env);
+
+ if (!cpu_isar_feature(aa64_gcs, cpu)) {
+ return -TARGET_EINVAL;
+ }
+ return put_user_ual(gcs_get_el0_mode(env), arg2);
+}
+#define do_prctl_get_shadow_stack_status do_prctl_get_shadow_stack_status
+
+static abi_long gcs_alloc(abi_ulong hint, abi_ulong size)
+{
+ /*
+ * Without softmmu, we cannot protect GCS memory properly.
+ * Make do with normal read/write permissions. This at least allows
+ * emulation of correct programs which don't access the gcs stack
+ * with normal instructions.
+ */
+ return target_mmap(hint, size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS |
+ (hint ? MAP_FIXED_NOREPLACE : 0), -1, 0);
+}
+
+static abi_ulong gcs_new_stack(TaskState *ts)
+{
+ /* Use guest_stack_size as a proxy for RLIMIT_STACK. */
+ abi_ulong size = MIN(MAX(guest_stack_size / 2, TARGET_PAGE_SIZE), 2 * GiB);
+ abi_ulong base = gcs_alloc(0, size);
+
+ if (base == -1) {
+ return -1;
+ }
+
+ ts->gcs_base = base;
+ ts->gcs_size = size;
+ return base + size - 8;
+}
+
+static abi_long do_prctl_set_shadow_stack_status(CPUArchState *env,
+ abi_long new_mode)
+{
+ ARMCPU *cpu = env_archcpu(env);
+ TaskState *ts = get_task_state(env_cpu(env));
+ abi_long cur_mode;
+
+ if (!cpu_isar_feature(aa64_gcs, cpu)) {
+ return -TARGET_EINVAL;
+ }
+ if (new_mode & ~(PR_SHADOW_STACK_ENABLE |
+ PR_SHADOW_STACK_WRITE |
+ PR_SHADOW_STACK_PUSH)) {
+ return -TARGET_EINVAL;
+ }
+
+ cur_mode = gcs_get_el0_mode(env);
+ if ((new_mode ^ cur_mode) & ts->gcs_el0_locked) {
+ return -TARGET_EBUSY;
+ }
+
+ if (new_mode & ~cur_mode & PR_SHADOW_STACK_ENABLE) {
+ abi_long gcspr;
+
+ if (ts->gcs_base || env->cp15.gcspr_el[0]) {
+ return -EINVAL;
+ }
+ gcspr = gcs_new_stack(ts);
+ if (gcspr == -1) {
+ return -TARGET_ENOMEM;
+ }
+ env->cp15.gcspr_el[0] = gcspr;
+ }
+
+ gcs_set_el0_mode(env, new_mode);
+ arm_rebuild_hflags(env);
+ return 0;
+}
+#define do_prctl_set_shadow_stack_status do_prctl_set_shadow_stack_status
+
+static abi_long do_prctl_lock_shadow_stack_status(CPUArchState *env,
+ abi_long arg2)
+{
+ ARMCPU *cpu = env_archcpu(env);
+ TaskState *ts = get_task_state(env_cpu(env));
+
+ if (!cpu_isar_feature(aa64_gcs, cpu)) {
+ return -EINVAL;
+ }
+ ts->gcs_el0_locked |= arg2;
+ return 0;
+}
+#define do_prctl_lock_shadow_stack_status do_prctl_lock_shadow_stack_status
+
#endif /* AARCH64_TARGET_PRCTL_H */
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 0b19fa43e6..6f0bfa83db 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -126,6 +126,11 @@ struct TaskState {
/* Extra fields for semihosted binaries. */
abi_ulong heap_base;
abi_ulong heap_limit;
+#endif
+#if defined(TARGET_AARCH64)
+ vaddr gcs_base;
+ abi_ulong gcs_size;
+ abi_ulong gcs_el0_locked;
#endif
abi_ulong stack_base;
int used; /* non zero if used */
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 91360a072c..2f1e881046 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6351,6 +6351,11 @@ abi_long do_arch_prctl(CPUX86State *env, int code,
abi_ulong addr)
# define PR_SME_VL_LEN_MASK 0xffff
# define PR_SME_VL_INHERIT (1 << 17)
#endif
+#ifndef PR_GET_SHADOW_STACK_STATUS
+# define PR_GET_SHADOW_STACK_STATUS 74
+# define PR_SET_SHADOW_STACK_STATUS 75
+# define PR_LOCK_SHADOW_STACK_STATUS 76
+#endif
#include "target_prctl.h"
@@ -6397,6 +6402,15 @@ static abi_long do_prctl_inval1(CPUArchState *env,
abi_long arg2)
#ifndef do_prctl_sme_set_vl
#define do_prctl_sme_set_vl do_prctl_inval1
#endif
+#ifndef do_prctl_get_shadow_stack_status
+#define do_prctl_get_shadow_stack_status do_prctl_inval1
+#endif
+#ifndef do_prctl_set_shadow_stack_status
+#define do_prctl_set_shadow_stack_status do_prctl_inval1
+#endif
+#ifndef do_prctl_lock_shadow_stack_status
+#define do_prctl_lock_shadow_stack_status do_prctl_inval1
+#endif
static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
abi_long arg3, abi_long arg4, abi_long arg5)
@@ -6467,6 +6481,21 @@ static abi_long do_prctl(CPUArchState *env, abi_long
option, abi_long arg2,
return -TARGET_EINVAL;
}
return do_prctl_get_tagged_addr_ctrl(env);
+ case PR_GET_SHADOW_STACK_STATUS:
+ if (arg3 || arg4 || arg5) {
+ return -TARGET_EINVAL;
+ }
+ return do_prctl_get_shadow_stack_status(env, arg2);
+ case PR_SET_SHADOW_STACK_STATUS:
+ if (arg3 || arg4 || arg5) {
+ return -TARGET_EINVAL;
+ }
+ return do_prctl_set_shadow_stack_status(env, arg2);
+ case PR_LOCK_SHADOW_STACK_STATUS:
+ if (arg3 || arg4 || arg5) {
+ return -TARGET_EINVAL;
+ }
+ return do_prctl_lock_shadow_stack_status(env, arg2);
case PR_GET_UNALIGN:
return do_prctl_get_unalign(env, arg2);
--
2.43.0
