From f543c2a3f7cec674f33079d75d71310d1c3ddaff Mon Sep 17 00:00:00 2001
From: Alan Jowett <alan.jowett@microsoft.com>
Date: Tue, 22 Jun 2021 15:29:18 -0600
Subject: [PATCH] ubpf_exec should separate errors returned from the return
 value

Signed-off-by: Alan Jowett <alan.jowett@microsoft.com>
---
 vm/inc/ubpf.h |  2 +-
 vm/test.c     |  3 ++-
 vm/ubpf_vm.c  | 21 +++++++++++----------
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/vm/inc/ubpf.h b/vm/inc/ubpf.h
index 1d9472bf1..cd189057f 100644
--- a/vm/inc/ubpf.h
+++ b/vm/inc/ubpf.h
@@ -98,7 +98,7 @@ int ubpf_load(struct ubpf_vm *vm, const void *code, uint32_t code_len, char **er
  */
 int ubpf_load_elf(struct ubpf_vm *vm, const void *elf, size_t elf_len, char **errmsg);
 
-uint64_t ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len);
+int ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len, uint64_t* bpf_return_value);
 
 ubpf_jit_fn ubpf_compile(struct ubpf_vm *vm, char **errmsg);
 
diff --git a/vm/test.c b/vm/test.c
index c7ae9a839..74e99191b 100644
--- a/vm/test.c
+++ b/vm/test.c
@@ -139,7 +139,8 @@ int main(int argc, char **argv)
         }
         ret = fn(mem, mem_len);
     } else {
-        ret = ubpf_exec(vm, mem, mem_len);
+        if (ubpf_exec(vm, mem, mem_len, &ret) < 0)
+            ret = UINT64_MAX;
     }
 
     printf("0x%"PRIx64"\n", ret);
diff --git a/vm/ubpf_vm.c b/vm/ubpf_vm.c
index 2709635e0..830b691d4 100644
--- a/vm/ubpf_vm.c
+++ b/vm/ubpf_vm.c
@@ -143,8 +143,8 @@ u32(uint64_t x)
     return x;
 }
 
-uint64_t
-ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
+int 
+ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len, uint64_t* bpf_return_value)
 {
     uint16_t pc = 0;
     const struct ebpf_inst *insts = vm->insts;
@@ -153,7 +153,7 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
 
     if (!insts) {
         /* Code must be loaded before we can execute */
-        return UINT64_MAX;
+        return -1;
     }
 
     reg[1] = (uintptr_t)mem;
@@ -195,7 +195,7 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
         case EBPF_OP_DIV_REG:
             if (reg[inst.src] == 0) {
                 vm->error_printf(stderr, "uBPF error: division by zero at PC %u\n", cur_pc);
-                return UINT64_MAX;
+                return -1;
             }
             reg[inst.dst] = u32(reg[inst.dst]) / u32(reg[inst.src]);
             reg[inst.dst] &= UINT32_MAX;
@@ -243,7 +243,7 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
         case EBPF_OP_MOD_REG:
             if (reg[inst.src] == 0) {
                 vm->error_printf(stderr, "uBPF error: division by zero at PC %u\n", cur_pc);
-                return UINT64_MAX;
+                return -1;
             }
             reg[inst.dst] = u32(reg[inst.dst]) % u32(reg[inst.src]);
             break;
@@ -316,7 +316,7 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
         case EBPF_OP_DIV64_REG:
             if (reg[inst.src] == 0) {
                 vm->error_printf(stderr, "uBPF error: division by zero at PC %u\n", cur_pc);
-                return UINT64_MAX;
+                return -1;
             }
             reg[inst.dst] /= reg[inst.src];
             break;
@@ -353,7 +353,7 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
         case EBPF_OP_MOD64_REG:
             if (reg[inst.src] == 0) {
                 vm->error_printf(stderr, "uBPF error: division by zero at PC %u\n", cur_pc);
-                return UINT64_MAX;
+                return -1;
             }
             reg[inst.dst] %= reg[inst.src];
             break;
@@ -384,13 +384,13 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
 #define BOUNDS_CHECK_LOAD(size) \
     do { \
         if (!bounds_check(vm, (char *)reg[inst.src] + inst.offset, size, "load", cur_pc, mem, mem_len, stack)) { \
-            return UINT64_MAX; \
+            return -1; \
         } \
     } while (0)
 #define BOUNDS_CHECK_STORE(size) \
     do { \
         if (!bounds_check(vm, (char *)reg[inst.dst] + inst.offset, size, "store", cur_pc, mem, mem_len, stack)) { \
-            return UINT64_MAX; \
+            return -1; \
         } \
     } while (0)
 
@@ -563,7 +563,8 @@ ubpf_exec(const struct ubpf_vm *vm, void *mem, size_t mem_len)
             }
             break;
         case EBPF_OP_EXIT:
-            return reg[0];
+            *bpf_return_value = reg[0];
+            return 0;
         case EBPF_OP_CALL:
             reg[0] = vm->ext_funcs[inst.imm](reg[1], reg[2], reg[3], reg[4], reg[5]);
             break;