[PULL 3/3] linux-user/aarch64: Fix SHADOW_STACK_SET_TOKEN

[Helge Deller <deller@kernel.org>]

From: Richard Henderson <richard.henderson@linaro.org>

The token is not computed via TARGET_PAGE_SIZE, but via a fixed 12-bit field.

Cc: qemu-stable@nongnu.org
Fixes: ad1afe433fa ("linux-user/aarch64: Implement map_shadow_stack syscall")
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4106
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
Signed-off-by: Helge Deller <deller@gmx.de>
---
 linux-user/syscall.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 547784d971..dc028686f4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6900,7 +6900,8 @@ static abi_long do_map_shadow_stack(CPUArchState *env, abi_ulong addr,
                 /* Leave an extra empty frame at top-of-stack. */
                 cap_ptr -= 8;
             }
-            cap_val = (cap_ptr & TARGET_PAGE_MASK) | 1;
+            /* Note the 12 bit field is unaffected by current page size. */
+            cap_val = deposit64(cap_ptr, 0, 12, 1);
             if (put_user_u64(cap_val, cap_ptr)) {
                 /* Allocation succeeded above. */
                 g_assert_not_reached();
-- 
2.54.0