[pypy-commit] pypy vmprof: here are drangons: a libunwind workaround to walk past JIT frames; it still needs a good integration with the JIT, to know which memory regions correspond to JIT code and how big is the stack in each (right now we simply assume it's 19 words)

[antocuni]

Author: Antonio Cuni <anto.c...@gmail.com>
Branch: vmprof
Changeset: r74230:15b900c687b8
Date: 2014-10-25 16:48 +0100
http://bitbucket.org/pypy/pypy/changeset/15b900c687b8/

Log:    here are drangons: a libunwind workaround to walk past JIT frames;
        it still needs a good integration with the JIT, to know which memory
        regions correspond to JIT code and how big is the stack in each
        (right now we simply assume it's 19 words)

diff --git a/pypy/module/_vmprof/src/vmprof.c b/pypy/module/_vmprof/src/vmprof.c
--- a/pypy/module/_vmprof/src/vmprof.c
+++ b/pypy/module/_vmprof/src/vmprof.c
@@ -72,6 +72,62 @@
 }
 
 
+/* ******************************************************
+ * libunwind workaround for process JIT frames correctly
+ * ******************************************************
+ */
+
+static void* jit_start;
+static void* jit_end;
+void vmprof_set_jit_range(void* start, void* end) {
+    printf("vmprof JIT range: %p-%p\n", start, end);
+    jit_start = start;
+    jit_end = end;
+}
+
+static ptrdiff_t vmprof_unw_get_custom_offset(void* ip) {
+    /* temporary hack to determine is this particular frame is JITted or not */
+    if (ip >= jit_start && ip <= jit_end) {
+        // it's probably a JIT frame
+        return 19*8; // XXX
+    }
+    return -1; // not JITted code
+}
+
+
+typedef struct {
+    void* _unused1;
+    void* _unused2;
+    void* sp;
+    void* ip;
+    void* _unused3[sizeof(unw_cursor_t)/sizeof(void*) - 4];
+} vmprof_hacked_unw_cursor_t;
+
+static int vmprof_unw_step(unw_cursor_t *cp) {
+       void* ip;
+    void* sp;
+    ptrdiff_t sp_offset;
+    unw_get_reg (cp, UNW_REG_IP, (unw_word_t*)&ip);
+    unw_get_reg (cp, UNW_REG_SP, (unw_word_t*)&sp);
+    sp_offset = vmprof_unw_get_custom_offset(ip);
+    if (sp_offset == -1) {
+        // it means that the ip is NOT in JITted code, so we can use the
+        // stardard unw_step
+        return unw_step(cp);
+    }
+    else {
+        // this is a horrible hack to manually walk the stack frame, by
+        // setting the IP and SP in the cursor
+        vmprof_hacked_unw_cursor_t *cp2 = (vmprof_hacked_unw_cursor_t*)cp;
+        void* bp = (void*)sp + sp_offset;
+        cp2->sp = bp+8; // the ret will pop a word, so the SP of the caller is
+                        // 8 bytes away from us
+        cp2->ip = ((void**)bp)[0]; // the ret is on the top of the stack
+        return 1;
+    }
+}
+
+
 /* *************************************************************
  * functions to dump the stack trace
  * *************************************************************
@@ -131,7 +187,7 @@
         }
 
         result[n++] = ip;
-        if (unw_step(&cursor) <= 0) {
+        if (vmprof_unw_step(&cursor) <= 0) {
             break;
         }
     }
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