[PATCH v2 08/24] linux-user/syscall: introduce prctl for indirect branch tracking

[Deepak Gupta <debug@rivosinc.com>]

Each application enables indirect branch tracking (forward cfi) for itself
via prctl. Adding branch tracking prctl in linux-user/syscall.

Using same prctl code as proposed in cfi patches in kernel mailing list [1]

[1] - https://lore.kernel.org/all/20240403234054.2020347-1-debug@rivosinc.com/

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Co-developed-by: Jim Shu <jim.shu@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Co-developed-by: Jesse Huang <jesse.huang@sifive.com>
---
 linux-user/syscall.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index b8c278b91d..ec157c1088 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6295,6 +6295,17 @@ abi_long do_arch_prctl(CPUX86State *env, int code, abi_ulong addr)
 # define PR_SME_VL_INHERIT   (1 << 17)
 #endif
 
+#ifndef PR_GET_INDIR_BR_LP_STATUS
+# define PR_GET_INDIR_BR_LP_STATUS      74
+#endif
+#ifndef PR_SET_INDIR_BR_LP_STATUS
+# define PR_SET_INDIR_BR_LP_STATUS      75
+# define PR_INDIR_BR_LP_ENABLE          (1UL << 0)
+#endif
+#ifndef PR_LOCK_INDIR_BR_LP_STATUS
+# define PR_LOCK_INDIR_BR_LP_STATUS     76
+#endif
+
 #include "target_prctl.h"
 
 static abi_long do_prctl_inval0(CPUArchState *env)
@@ -6477,6 +6488,14 @@ static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
     case PR_SET_TSC:
         /* Disable to prevent the target disabling stuff we need. */
         return -TARGET_EINVAL;
+    case PR_GET_INDIR_BR_LP_STATUS:
+    case PR_SET_INDIR_BR_LP_STATUS:
+    case PR_LOCK_INDIR_BR_LP_STATUS:
+#ifndef do_prctl_cfi
+        return do_prctl_inval1(env, arg2);
+#else
+        return do_prctl_cfi(env, option, arg2);
+#endif
 
     default:
         qemu_log_mask(LOG_UNIMP, "Unsupported prctl: " TARGET_ABI_FMT_ld "\n",
-- 
2.44.0