Changes in kernel/arch/mips32/src/debug/stacktrace.c [76e1121f:63bdde6] in mainline

File:

• kernel/arch/mips32/src/debug/stacktrace.c (modified) (5 diffs)

kernel/arch/mips32/src/debug/stacktrace.c

@@ -33 +33 @@
  */
 
-/*
- * This stack tracing code is based on the suggested algorithm described on page
- * 3-27 and 3-28 of:
- * 
- * SYSTEM V
- * APPLICATION BINARY INTERFACE
- *
- * MIPS RISC Processor
- * Supplement
- * 3rd Edition
- *
- * Unfortunately, GCC generates code which is not entirely compliant with this
- * method. For example, it places the "jr ra" instruction quite arbitrarily in
- * the middle of the function which makes the original algorithm unapplicable.
- *
- * We deal with this problem by simply not using those parts of the algorithm
- * that rely on the "jr ra" instruction occurring in the last basic block of a
- * function, which gives us still usable, but less reliable stack tracer. The
- * unreliability stems from the fact that under some circumstances it can become
- * confused and produce incorrect or incomplete stack trace. We apply extra
- * sanity checks so that the algorithm is still safe and should not crash the
- * system.
- *
- * Even though not perfect, our solution is pretty lightweight, especially when
- * compared with a prospective alternative solution based on additional
- * debugging information stored directly in the kernel image.
- */
-
 #include <stacktrace.h>
 #include <syscall/copy.h>
@@ -124 +96 @@
 extern char ktext_end;
 
-static bool bounds_check(uintptr_t pc)
-{
-        return (pc >= (uintptr_t) &ktext_start) &&
-            (pc < (uintptr_t) &ktext_end);
-}
-
 static bool
 scan(stack_trace_context_t *ctx, uintptr_t *prev_fp, uintptr_t *prev_ra)
@@ -140 +106 @@
         do {
                 inst--;
-                if (!bounds_check((uintptr_t) inst))
-                        return false;
 #if 0
                 /*
@@ -216 +180 @@
                                         return false;
                                 /* too big offsets are suspicious */
-                                if ((size_t) offset > sizeof(istate_t))
+                                if (offset > 32 * 4)
                                         return false;
 
@@ -243 +207 @@
 {
         return !((ctx->fp == 0) || ((ctx->fp % 8) != 0) ||
-            (ctx->pc % 4 != 0) || !bounds_check(ctx->pc));
+            (ctx->pc % 4 != 0) || (ctx->pc < (uintptr_t) &ktext_start) ||
+            (ctx->pc >= (uintptr_t) &ktext_end));
 }