[PATCH v2 12/45] test: Support testing malloc() failures

[Simon Glass]

Hi Sean,

On Wed, 28 Sept 2022 at 15:50, Sean Anderson <seanga2 at gmail.com> wrote:
>
> On 9/28/22 17:06, Simon Glass wrote:
> > Hi Sean,
> >
> > On Wed, 28 Sept 2022 at 11:18, Sean Anderson <seanga2 at gmail.com> wrote:
> >>
> >> On 9/6/22 22:27, Simon Glass wrote:
> >>> It is helpful to test that out-of-memory checks work correctly in code
> >>> that calls malloc().
> >>>
> >>> Add a simple way to force failure after a given number of malloc() calls.
> >>>
> >>> Fix a header guard to avoid a build error on sandbox_vpl.
> >>>
> >>> Signed-off-by: Simon Glass <sjg at chromium.org>
> >>> ---
> >>>
> >>> (no changes since v1)
> >>>
> >>>    arch/sandbox/include/asm/malloc.h |  1 +
> >>>    common/dlmalloc.c                 | 19 +++++++++++++++++++
> >>>    include/malloc.h                  | 12 ++++++++++++
> >>>    test/test-main.c                  |  1 +
> >>>    4 files changed, 33 insertions(+)
> >>>
> >>> diff --git a/arch/sandbox/include/asm/malloc.h b/arch/sandbox/include/asm/malloc.h
> >>> index a1467b5eadd..8aaaa9cb87b 100644
> >>> --- a/arch/sandbox/include/asm/malloc.h
> >>> +++ b/arch/sandbox/include/asm/malloc.h
> >>> @@ -6,6 +6,7 @@
> >>>     */
> >>>
> >>>    #ifndef __ASM_MALLOC_H
> >>> +#define __ASM_MALLOC_H
> >>>
> >>>    void *malloc(size_t size);
> >>>    void free(void *ptr);
> >>> diff --git a/common/dlmalloc.c b/common/dlmalloc.c
> >>> index f48cd2a333d..41c7230424c 100644
> >>> --- a/common/dlmalloc.c
> >>> +++ b/common/dlmalloc.c
> >>> @@ -596,6 +596,9 @@ ulong mem_malloc_start = 0;
> >>>    ulong mem_malloc_end = 0;
> >>>    ulong mem_malloc_brk = 0;
> >>>
> >>> +static bool malloc_testing;  /* enable test mode */
> >>> +static int malloc_max_allocs;        /* return NULL after this many calls to malloc() */
> >>> +
> >>>    void *sbrk(ptrdiff_t increment)
> >>>    {
> >>>        ulong old = mem_malloc_brk;
> >>> @@ -1307,6 +1310,11 @@ Void_t* mALLOc(bytes) size_t bytes;
> >>>                return malloc_simple(bytes);
> >>>    #endif
> >>>
> >>> +  if (CONFIG_IS_ENABLED(UNIT_TEST) && malloc_testing) {
> >>> +    if (--malloc_max_allocs < 0)
> >>> +      return NULL;
> >>> +  }
> >>> +
> >>>      /* check if mem_malloc_init() was run */
> >>>      if ((mem_malloc_start == 0) && (mem_malloc_end == 0)) {
> >>>        /* not initialized yet */
> >>> @@ -2470,6 +2478,17 @@ int initf_malloc(void)
> >>>        return 0;
> >>>    }
> >>>
> >>> +void malloc_enable_testing(int max_allocs)
> >>> +{
> >>> +     malloc_testing = true;
> >>> +     malloc_max_allocs = max_allocs;
> >>> +}
> >>> +
> >>> +void malloc_disable_testing(void)
> >>> +{
> >>> +     malloc_testing = false;
> >>> +}
> >>> +
> >>>    /*
> >>>
> >>>    History:
> >>> diff --git a/include/malloc.h b/include/malloc.h
> >>> index e8c8b254c0d..161ccbd1298 100644
> >>> --- a/include/malloc.h
> >>> +++ b/include/malloc.h
> >>> @@ -883,6 +883,18 @@ extern Void_t*     sbrk();
> >>>
> >>>    void malloc_simple_info(void);
> >>>
> >>> +/**
> >>> + * malloc_enable_testing() - Put malloc() into test mode
> >>> + *
> >>> + * This only works if UNIT_TESTING is enabled
> >>> + *
> >>> + * @max_allocs: return -ENOMEM after max_allocs calls to malloc()
> >>> + */
> >>> +void malloc_enable_testing(int max_allocs);
> >>> +
> >>> +/** malloc_disable_testing() - Put malloc() into normal mode */
> >>> +void malloc_disable_testing(void);
> >>> +
> >>>    #if CONFIG_IS_ENABLED(SYS_MALLOC_SIMPLE)
> >>>    #define malloc malloc_simple
> >>>    #define realloc realloc_simple
> >>> diff --git a/test/test-main.c b/test/test-main.c
> >>> index c65cbd7c351..5b6b5ba5bbe 100644
> >>> --- a/test/test-main.c
> >>> +++ b/test/test-main.c
> >>> @@ -46,6 +46,7 @@ static int dm_test_pre_run(struct unit_test_state *uts)
> >>>        uts->force_fail_alloc = false;
> >>>        uts->skip_post_probe = false;
> >>>        gd->dm_root = NULL;
> >>> +     malloc_disable_testing();
> >>>        if (CONFIG_IS_ENABLED(UT_DM) && !CONFIG_IS_ENABLED(OF_PLATDATA))
> >>>                memset(dm_testdrv_op_count, '\0', sizeof(dm_testdrv_op_count));
> >>>        arch_reset_for_test();
> >>
> >> Reviewed-by: Sean Anderson <seanga2 at gmail.com>
> >>
> >> but do we need to instrument rEALLOc too?
> >
> > We could, but I'd prefer to have a test which needs it first. Actually
> > realloc() calls malloc() in some cases, so we are already messing with
> > things here.
>
> Maybe it would be better to do this at the "top-level" instead. E.g.
> redefine the malloc() et al macro. That way we remove any double-counting.

Yes, that makes sense. But again, I'd rather do this when we have a
use case for making realloc() fail.

BTW has dlmalloc been updated in recent years?

Regards,
Simon

>
> --Sean
>