build(canary): support libcalls

Author: bboilot-ledger

src/stack_protector_init.S

@@ -10,6 +10,11 @@
 .global __wrap___stack_chk_init
 .thumb_func
 __wrap___stack_chk_init:
+    // if r0 != 0, skip initialization and jump directly to main
+    // (don't overwrite parent canary during a libcall)
+    cmp r0, #0
+    bne 1f
+
     // save arguments passed to main
     push {r0-r3}
 

target/apex_m/script.ld

@@ -107,10 +107,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;
 

target/apex_p/script.ld

@@ -107,10 +107,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;
 

target/flex/script.ld

@@ -110,10 +110,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;
 

target/nanos2/script.ld

@@ -109,10 +109,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;
 

target/nanox/script.ld

@@ -109,10 +109,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;
 

target/stax/script.ld

@@ -110,10 +110,10 @@ SECTIONS
     /**
      * Place RAM uninitialized variables
      */
-    _bss = .;
     __stack_chk_guard = .;
     PROVIDE(__stack_chk_guard = .);
     . += 4;
+    _bss = .;
     *(.bss*)
     _ebss = .;