From 2b80ab425b266e1b6f61a74b8ee1f04b6b6213bf Mon Sep 17 00:00:00 2001
From: Robert Xiao <brx@cs.ubc.ca>
Date: Fri, 16 Jun 2023 14:47:03 -0700
Subject: [PATCH] Return new UC_ERR_OVERFLOW instead of UC_ERR_NOMEM when reg
 buffer is too small

---
 include/unicorn/unicorn.h | 21 +++++++++++++--------
 qemu/unicorn_common.h     |  2 +-
 uc.c                      |  2 ++
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/include/unicorn/unicorn.h b/include/unicorn/unicorn.h
index dbe8d027..3814b8e0 100644
--- a/include/unicorn/unicorn.h
+++ b/include/unicorn/unicorn.h
@@ -192,6 +192,7 @@ typedef enum uc_err {
     UC_ERR_HOOK_EXIST,      // hook for this event already existed
     UC_ERR_RESOURCE,        // Insufficient resource: uc_emu_start()
     UC_ERR_EXCEPTION,       // Unhandled CPU exception
+    UC_ERR_OVERFLOW,        // Provided buffer is not large enough: uc_reg_*2()
 } uc_err;
 
 /*
@@ -807,7 +808,7 @@ uc_err uc_reg_read(uc_engine *uc, int regid, void *value);
  @size:   size of value being written; on return, size of value written
 
  @return UC_ERR_OK on success; UC_ERR_ARG if register number or value is
- invalid; UC_ERR_NOMEM if value is not large enough.
+ invalid; UC_ERR_OVERFLOW if value is not large enough for the register.
 */
 UNICORN_EXPORT
 uc_err uc_reg_write2(uc_engine *uc, int regid, const void *value, size_t *size);
@@ -821,7 +822,7 @@ uc_err uc_reg_write2(uc_engine *uc, int regid, const void *value, size_t *size);
  @size:   size of value buffer; on return, size of value read
 
  @return UC_ERR_OK on success; UC_ERR_ARG if register number or value is
- invalid; UC_ERR_NOMEM if value is not large enough.
+ invalid; UC_ERR_OVERFLOW if value is not large enough to hold the register.
 */
 UNICORN_EXPORT
 uc_err uc_reg_read2(uc_engine *uc, int regid, void *value, size_t *size);
@@ -865,7 +866,8 @@ uc_err uc_reg_read_batch(uc_engine *uc, int *regs, void **vals, int count);
  @count: length of *regs, *vals and *sizes
 
  @return UC_ERR_OK on success; UC_ERR_ARG if some register number or value is
- invalid; UC_ERR_NOMEM if some value is not large enough.
+ invalid; UC_ERR_OVERFLOW if some value is not large enough for the
+ corresponding register.
 */
 UNICORN_EXPORT
 uc_err uc_reg_write_batch2(uc_engine *uc, int *regs, const void *const *vals,
@@ -882,7 +884,8 @@ uc_err uc_reg_write_batch2(uc_engine *uc, int *regs, const void *const *vals,
  @count: length of *regs, *vals and *sizes
 
  @return UC_ERR_OK on success; UC_ERR_ARG if some register number or value is
- invalid; UC_ERR_NOMEM if some value is not large enough.
+ invalid; UC_ERR_OVERFLOW if some value is not large enough to hold the
+ corresponding register.
 */
 UNICORN_EXPORT
 uc_err uc_reg_read_batch2(uc_engine *uc, int *regs, void *const *vals,
@@ -1218,7 +1221,7 @@ uc_err uc_context_reg_read(uc_context *ctx, int regid, void *value);
  @size:   size of value being written; on return, size of value written
 
  @return UC_ERR_OK on success; UC_ERR_ARG if register number or value is
- invalid; UC_ERR_NOMEM if value is not large enough.
+ invalid; UC_ERR_OVERFLOW if value is not large enough for the register.
 */
 UNICORN_EXPORT
 uc_err uc_context_reg_write2(uc_context *ctx, int regid, const void *value,
@@ -1233,7 +1236,7 @@ uc_err uc_context_reg_write2(uc_context *ctx, int regid, const void *value,
  @size:   size of value buffer; on return, size of value read
 
  @return UC_ERR_OK on success; UC_ERR_ARG if register number or value is
- invalid; UC_ERR_NOMEM if value is not large enough.
+ invalid; UC_ERR_OVERFLOW if value is not large enough to hold the register.
 */
 UNICORN_EXPORT
 uc_err uc_context_reg_read2(uc_context *ctx, int regid, void *value,
@@ -1279,7 +1282,8 @@ uc_err uc_context_reg_read_batch(uc_context *ctx, int *regs, void **vals,
  @count: length of *regs, *vals and *sizes
 
  @return UC_ERR_OK on success; UC_ERR_ARG if some register number or value is
- invalid; UC_ERR_NOMEM if some value is not large enough.
+ invalid; UC_ERR_OVERFLOW if some value is not large enough for the
+ corresponding register.
 */
 UNICORN_EXPORT
 uc_err uc_context_reg_write_batch2(uc_context *ctx, int *regs,
@@ -1297,7 +1301,8 @@ uc_err uc_context_reg_write_batch2(uc_context *ctx, int *regs,
  @count: length of *regs, *vals and *sizes
 
  @return UC_ERR_OK on success; UC_ERR_ARG if some register number or value is
- invalid; UC_ERR_NOMEM if some value is not large enough.
+ invalid; UC_ERR_OVERFLOW if some value is not large enough to hold the
+ corresponding register.
 */
 UNICORN_EXPORT
 uc_err uc_context_reg_read_batch2(uc_context *ctx, int *regs, void *const *vals,
diff --git a/qemu/unicorn_common.h b/qemu/unicorn_common.h
index 035fe061..1a622fe7 100644
--- a/qemu/unicorn_common.h
+++ b/qemu/unicorn_common.h
@@ -131,7 +131,7 @@ static inline void uc_common_init(struct uc_struct* uc)
 
 #define CHECK_REG_TYPE(type) do {             \
     if (unlikely(*size < sizeof(type))) {     \
-        return UC_ERR_NOMEM;                  \
+        return UC_ERR_OVERFLOW;               \
     }                                         \
     *size = sizeof(type);                     \
     ret = UC_ERR_OK;                          \
diff --git a/uc.c b/uc.c
index 0c7a8f32..b92dddc1 100644
--- a/uc.c
+++ b/uc.c
@@ -148,6 +148,8 @@ const char *uc_strerror(uc_err code)
         return "Insufficient resource (UC_ERR_RESOURCE)";
     case UC_ERR_EXCEPTION:
         return "Unhandled CPU exception (UC_ERR_EXCEPTION)";
+    case UC_ERR_OVERFLOW:
+        return "Provided buffer is too small (UC_ERR_OVERFLOW)";
     }
 }