File 0183-erts-Protect-erts_debug_SUITE-stack_check-... of Package erlang

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File 0183-erts-Protect-erts_debug_SUITE-stack_check-against-lo.patch of Package erlang (Revision 164a9a2c05a0bec780d638345baeb078)

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From 33735d78ebc4d049d170ad709c1de0a014f6bd87 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Tue, 1 Jun 2021 12:20:55 +0200
Subject: [PATCH 3/3] erts: Protect erts_debug_SUITE:stack_check against
 looping

---
 erts/emulator/beam/beam_debug.c         | 20 ++++++++++++++++----
 erts/emulator/beam/erl_bif_info.c       |  4 ++--
 erts/emulator/beam/global.h             |  4 ++--
 erts/emulator/test/erts_debug_SUITE.erl |  1 +
 4 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/erts/emulator/beam/beam_debug.c b/erts/emulator/beam/beam_debug.c
index b790aeaff8..a50ec46659 100644
--- a/erts/emulator/beam/beam_debug.c
+++ b/erts/emulator/beam/beam_debug.c
@@ -1313,27 +1313,39 @@ ms_wait(Process *c_p, Eterm etimeout, int busy)
  */
 
 UWord
-erts_check_stack_recursion_downwards(char *start_c)
+erts_check_stack_recursion_downwards(char *start_c, char* prev_c)
 {
     char *limit = ERTS_STACK_LIMIT;
     char c;
     UWord res;
+
+    if (prev_c == &c) {
+         /* Protect against eternal loop if C compiler do tail call
+            optimization. This may also prevent such optimizations. */
+        return 0;
+    }
     if (erts_check_below_limit(&c, limit + 1024))
         return (char *) erts_ptr_id(start_c) - (char *) erts_ptr_id(&c);
-    res = erts_check_stack_recursion_downwards(start_c);
+    res = erts_check_stack_recursion_downwards(start_c, &c);
     erts_ptr_id(&c);
     return res;
 }
 
 UWord
-erts_check_stack_recursion_upwards(char *start_c)
+erts_check_stack_recursion_upwards(char *start_c, char* prev_c)
 {
     char *limit = ERTS_STACK_LIMIT;
     char c;
     UWord res;
+
+    if (prev_c == &c) {
+         /* Protect against eternal loop if C compiler do tail call
+            optimization. This may also prevent such optimizations. */
+        return 0;
+    }
     if (erts_check_above_limit(&c, limit - 1024))
         return (char *) erts_ptr_id(&c) - (char *) erts_ptr_id(start_c);
-    res = erts_check_stack_recursion_upwards(start_c);
+    res = erts_check_stack_recursion_upwards(start_c, &c);
     erts_ptr_id(&c);
     return res;
 }
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index 93ce1aace9..cb1af1f008 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -4102,9 +4102,9 @@ BIF_RETTYPE erts_debug_get_internal_state_1(BIF_ALIST_1)
             UWord size;
             char c;
             if (erts_is_above_stack_limit(&c))
-                size = erts_check_stack_recursion_downwards(&c);
+                size = erts_check_stack_recursion_downwards(&c, &c);
             else
-                size = erts_check_stack_recursion_upwards(&c);
+                size = erts_check_stack_recursion_upwards(&c, &c);
 	    if (IS_SSMALL(size))
 		BIF_RET(make_small(size));
 	    else {
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 7c1f3a0899..1dcfbf3a71 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -1475,8 +1475,8 @@ void erts_init_external(void);
 void erts_init_map(void);
 
 /* beam_debug.c */
-UWord erts_check_stack_recursion_downwards(char *start_c);
-UWord erts_check_stack_recursion_upwards(char *start_c);
+UWord erts_check_stack_recursion_downwards(char *start_c, char *prev_c);
+UWord erts_check_stack_recursion_upwards(char *start_c, char *prev_c);
 int erts_is_above_stack_limit(char *ptr);
 
 /* erl_unicode.c */
diff --git a/erts/emulator/test/erts_debug_SUITE.erl b/erts/emulator/test/erts_debug_SUITE.erl
index f3b72fa972..2c1e83dbdf 100644
--- a/erts/emulator/test/erts_debug_SUITE.erl
+++ b/erts/emulator/test/erts_debug_SUITE.erl
@@ -232,6 +232,7 @@ stack_check(Config) when is_list(Config) ->
     %% by PCRE). VM will crash if it doesn't work...
     Size = erts_debug:get_internal_state(stack_check),
     erts_debug:set_internal_state(available_internal_state,false),
+    true = (is_integer(Size) and (Size > 0)),
     {comment, "Stack size: "++integer_to_list(Size)++" bytes"}.
 
 df_smoke([M|Ms]) ->
-- 
2.26.2

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File 0183-erts-Protect-erts_debug_SUITE-stack_check-against-lo.patch of Package erlang (Revision 164a9a2c05a0bec780d638345baeb078)

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