opencsd: etmv4: Optional limit on number of instructions in range.

Adds an optional  limit on the number of instructions that will be allow in a single instruciton
range.

Limit not used unless an environment variable "OPENCSD_INSTR_RANGE_LIMIT" is set.

Use to debug possible decoder runaway if incorrect program image supplied
to decoder is suspected.

Signed-off-by: Mike Leach <mike.leach@linaro.org>

4 files changed, 34 insertions, 0 deletions

diff --git a/decoder/include/opencsd/etmv4/trc_pkt_decode_etmv4i.h b/decoder/include/opencsd/etmv4/trc_pkt_decode_etmv4i.h
index 7838ece04e57..9b6f5311a883 100644
--- a/decoder/include/opencsd/etmv4/trc_pkt_decode_etmv4i.h
+++ b/decoder/include/opencsd/etmv4/trc_pkt_decode_etmv4i.h
@@ -43,6 +43,8 @@
 #include "common/ocsd_gen_elem_stack.h"
 #include "opencsd/etmv4/trc_etmv4_stack_elem.h"
 
+#define OCSD_ENV_INSTR_RANGE_LIMIT "OPENCSD_INSTR_RANGE_LIMIT"
+
 class TrcStackElem;
 class TrcStackElemParam;
 class TrcStackElemCtxt;
@@ -130,6 +132,12 @@ private:
         WP_NACC
     } WP_res_t;
 
+    /* Optional run limit for decoded instruction range. 
+     * Throw error if limit exceeded. Set by env var - use for debugging decode runs 
+     * which may be running away due to bad data
+     */
+    int m_num_instr_range_limit;
+
     typedef struct {
         ocsd_vaddr_t st_addr;
         ocsd_vaddr_t en_addr;
diff --git a/decoder/include/opencsd/ocsd_if_types.h b/decoder/include/opencsd/ocsd_if_types.h
index 1af74c810fbe..cd96018cbb43 100644
--- a/decoder/include/opencsd/ocsd_if_types.h
+++ b/decoder/include/opencsd/ocsd_if_types.h
@@ -134,6 +134,7 @@ typedef enum _ocsd_err_t {
     OCSD_ERR_DCD_INTERFACE_UNUSED,      /**< 43 Attempt to connect or use and interface not supported by this decoder. */
     /* additional errors */
     OCSD_ERR_INVALID_OPCODE,            /**< 44 Opcode found while decoding program memory is illegal */
+    OCSD_ERR_I_RANGE_LIMIT_OVERRUN,     /**< 45 An optional limit on consecutive instructions in range during decode has been exceeded. */
     /* end marker*/
     OCSD_ERR_LAST
 } ocsd_err_t;
diff --git a/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp b/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
index d82bd5538713..b96301252c4e 100644
--- a/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
+++ b/decoder/source/etmv4/trc_pkt_decode_etmv4i.cpp
@@ -241,6 +241,20 @@ void TrcPktDecodeEtmV4I::initDecoder()
     m_CSID = 0;
     m_IASize64 = false;
 
+    // set debug range limit - look for debugging env var
+    char* env_var;
+    long env_val;
+
+    m_num_instr_range_limit = 0;
+    if ((env_var = getenv(OCSD_ENV_INSTR_RANGE_LIMIT)) != NULL)
+    {
+        env_val = strtol(env_var, NULL, 0);
+        /* if valid number set limit */
+        if (env_val > 0)
+            m_num_instr_range_limit = env_val;
+
+    }
+
     // elements associated with data trace
 #ifdef DATA_TRACE_SUPPORTED
     m_p0_key_max = 0;
@@ -1899,6 +1913,15 @@ ocsd_err_t TrcPktDecodeEtmV4I::traceInstrToWP(instr_range_t &range, WP_res_t &WP
             // not enough memory accessible.
             WPRes = WP_NACC;
         }
+
+        if (m_num_instr_range_limit)
+        {
+            if (range.num_instr > m_num_instr_range_limit)
+            {
+                err = OCSD_ERR_I_RANGE_LIMIT_OVERRUN;
+                LogError(ocsdError(OCSD_ERR_SEV_ERROR, err, "Decode Instruction Range Limit Overrun"));
+            }
+        }
     }
     // update the range decoded address in the output packet.
     range.en_addr = m_instr_info.instr_addr;
diff --git a/decoder/source/ocsd_error.cpp b/decoder/source/ocsd_error.cpp
index 952f94684cfe..3aee3724016e 100644
--- a/decoder/source/ocsd_error.cpp
+++ b/decoder/source/ocsd_error.cpp
@@ -91,10 +91,12 @@ static const char *s_errorCodeDescs[][2] = {
     {"OCSD_ERR_DCDREG_NAME_REPEAT","Attempted to register a decoder with the same name as another one."},
     {"OCSD_ERR_DCDREG_NAME_UNKNOWN","Attempted to find a decoder with a name that is not known in the library."},
     {"OCSD_ERR_DCDREG_TYPE_UNKNOWN","Attempted to find a decoder with a type that is not known in the library."},
+    {"OCSD_ERR_DCDREG_TOOMANY","Attempted to register too many custom decoders"},
     /* decoder config */
     {"OCSD_ERR_DCD_INTERFACE_UNUSED","Attempt to connect or use and interface not supported by this decoder."},
     /* additional errors */
     {"OCSD_ERR_INVALID_OPCODE","Illegal Opode found while decoding program memory."},
+    {"OCSD_ERR_I_RANGE_LIMIT_OVERRUN","An optional limit on consecutive instructions in range during decode has been exceeded."},
     /* end marker*/
     {"OCSD_ERR_LAST", "No error - error code end marker"}
 };