Ignore:
Timestamp:
2010-09-04T12:21:05Z (14 years ago)
Author:
Jakub Jermar <jakub@…>
Branches:
lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export
Children:
4687a26c, 5203efb1
Parents:
343f2b7e
Message:

Add an explanatory comment to mips32 stacktrace.c.

File:
1 edited

Legend:

Unmodified
Added
Removed
  • kernel/arch/mips32/src/debug/stacktrace.c

    r343f2b7e r76e1121f  
    3131 */
    3232/** @file
     33 */
     34
     35/*
     36 * This stack tracing code is based on the suggested algorithm described on page
     37 * 3-27 and 3-28 of:
     38 *
     39 * SYSTEM V
     40 * APPLICATION BINARY INTERFACE
     41 *
     42 * MIPS RISC Processor
     43 * Supplement
     44 * 3rd Edition
     45 *
     46 * Unfortunately, GCC generates code which is not entirely compliant with this
     47 * method. For example, it places the "jr ra" instruction quite arbitrarily in
     48 * the middle of the function which makes the original algorithm unapplicable.
     49 *
     50 * We deal with this problem by simply not using those parts of the algorithm
     51 * that rely on the "jr ra" instruction occurring in the last basic block of a
     52 * function, which gives us still usable, but less reliable stack tracer. The
     53 * unreliability stems from the fact that under some circumstances it can become
     54 * confused and produce incorrect or incomplete stack trace. We apply extra
     55 * sanity checks so that the algorithm is still safe and should not crash the
     56 * system.
     57 *
     58 * Even though not perfect, our solution is pretty lightweight, especially when
     59 * compared with a prospective alternative solution based on additional
     60 * debugging information stored directly in the kernel image.
    3361 */
    3462
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