[Qemu-devel] [PATCH v3 14/23] linux-user/aarch64: Use qemu_guest_getrandom for PAUTH keys

[Richard Henderson]

Use a better interface for random numbers than rand() * 3.

Cc: Laurent Vivier <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
 linux-user/aarch64/target_syscall.h |  2 --
 linux-user/aarch64/cpu_loop.c       | 29 ++++++---------------------
 linux-user/syscall.c                | 31 ++++++++++++++++++++++++-----
 3 files changed, 32 insertions(+), 30 deletions(-)

diff --git a/linux-user/aarch64/target_syscall.h 
b/linux-user/aarch64/target_syscall.h
index b595e5da82..995e475c73 100644
--- a/linux-user/aarch64/target_syscall.h
+++ b/linux-user/aarch64/target_syscall.h
@@ -29,6 +29,4 @@ struct target_pt_regs {
 # define TARGET_PR_PAC_APDBKEY   (1 << 3)
 # define TARGET_PR_PAC_APGAKEY   (1 << 4)
 
-void arm_init_pauth_key(ARMPACKey *key);
-
 #endif /* AARCH64_TARGET_SYSCALL_H */
diff --git a/linux-user/aarch64/cpu_loop.c b/linux-user/aarch64/cpu_loop.c
index d75fd9d3e2..cedad39ca0 100644
--- a/linux-user/aarch64/cpu_loop.c
+++ b/linux-user/aarch64/cpu_loop.c
@@ -20,6 +20,7 @@
 #include "qemu/osdep.h"
 #include "qemu.h"
 #include "cpu_loop-common.h"
+#include "qemu/guest-random.h"
 
 #define get_user_code_u32(x, gaddr, env)                \
     ({ abi_long __r = get_user_u32((x), (gaddr));       \
@@ -147,24 +148,6 @@ void cpu_loop(CPUARMState *env)
     }
 }
 
-static uint64_t arm_rand64(void)
-{
-    int shift = 64 - clz64(RAND_MAX);
-    int i, n = 64 / shift + (64 % shift != 0);
-    uint64_t ret = 0;
-
-    for (i = 0; i < n; i++) {
-        ret = (ret << shift) | rand();
-    }
-    return ret;
-}
-
-void arm_init_pauth_key(ARMPACKey *key)
-{
-    key->lo = arm_rand64();
-    key->hi = arm_rand64();
-}
-
 void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
 {
     ARMCPU *cpu = arm_env_get_cpu(env);
@@ -192,11 +175,11 @@ void target_cpu_copy_regs(CPUArchState *env, struct 
target_pt_regs *regs)
 #endif
 
     if (cpu_isar_feature(aa64_pauth, cpu)) {
-        arm_init_pauth_key(&env->apia_key);
-        arm_init_pauth_key(&env->apib_key);
-        arm_init_pauth_key(&env->apda_key);
-        arm_init_pauth_key(&env->apdb_key);
-        arm_init_pauth_key(&env->apga_key);
+        qemu_guest_getrandom_nofail(&env->apia_key, sizeof(ARMPACKey));
+        qemu_guest_getrandom_nofail(&env->apib_key, sizeof(ARMPACKey));
+        qemu_guest_getrandom_nofail(&env->apda_key, sizeof(ARMPACKey));
+        qemu_guest_getrandom_nofail(&env->apdb_key, sizeof(ARMPACKey));
+        qemu_guest_getrandom_nofail(&env->apga_key, sizeof(ARMPACKey));
     }
 
     ts->stack_base = info->start_stack;
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 8f7125cd67..c2168db1c8 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -111,6 +111,7 @@
 
 #include "qemu.h"
 #include "qemu/guest-random.h"
+#include "qapi/error.h"
 #include "fd-trans.h"
 
 #ifndef CLONE_IO
@@ -9731,25 +9732,45 @@ static abi_long do_syscall1(void *cpu_env, int num, 
abi_long arg1,
                     int all = (TARGET_PR_PAC_APIAKEY | TARGET_PR_PAC_APIBKEY |
                                TARGET_PR_PAC_APDAKEY | TARGET_PR_PAC_APDBKEY |
                                TARGET_PR_PAC_APGAKEY);
+                    int ret = 0;
+                    Error *err = NULL;
+
                     if (arg2 == 0) {
                         arg2 = all;
                     } else if (arg2 & ~all) {
                         return -TARGET_EINVAL;
                     }
                     if (arg2 & TARGET_PR_PAC_APIAKEY) {
-                        arm_init_pauth_key(&env->apia_key);
+                        ret |= qemu_guest_getrandom(&env->apia_key,
+                                                    sizeof(ARMPACKey), &err);
                     }
                     if (arg2 & TARGET_PR_PAC_APIBKEY) {
-                        arm_init_pauth_key(&env->apib_key);
+                        ret |= qemu_guest_getrandom(&env->apib_key,
+                                                    sizeof(ARMPACKey), &err);
                     }
                     if (arg2 & TARGET_PR_PAC_APDAKEY) {
-                        arm_init_pauth_key(&env->apda_key);
+                        ret |= qemu_guest_getrandom(&env->apda_key,
+                                                    sizeof(ARMPACKey), &err);
                     }
                     if (arg2 & TARGET_PR_PAC_APDBKEY) {
-                        arm_init_pauth_key(&env->apdb_key);
+                        ret |= qemu_guest_getrandom(&env->apdb_key,
+                                                    sizeof(ARMPACKey), &err);
                     }
                     if (arg2 & TARGET_PR_PAC_APGAKEY) {
-                        arm_init_pauth_key(&env->apga_key);
+                        ret |= qemu_guest_getrandom(&env->apga_key,
+                                                    sizeof(ARMPACKey), &err);
+                    }
+                    if (ret != 0) {
+                        /*
+                         * Some unknown failure in the crypto.  The best
+                         * we can do is log it and fail the syscall.
+                         * The real syscall cannot fail this way.
+                         */
+                        qemu_log_mask(LOG_UNIMP,
+                                      "PR_PAC_RESET_KEYS: Crypto failure: %s",
+                                      error_get_pretty(err));
+                        error_free(err);
+                        return -TARGET_EIO;
                     }
                     return 0;
                 }
-- 
2.17.2