Re: [RFC v5 034/126] MIPS Machines: introduce ERRP_AUTO_PROPAGATE

[Philippe Mathieu-Daudé]

Hi Vladimir,

On 10/11/19 6:04 PM, Vladimir Sementsov-Ogievskiy wrote:
> If we want to add some info to errp (by error_prepend() or
> error_append_hint()), we must use the ERRP_AUTO_PROPAGATE macro.
> Otherwise, this info will not be added when errp == &fatal_err
> (the program will exit prior to the error_append_hint() or
> error_prepend() call).  Fix such cases.
>
> If we want to check error after errp-function call, we need to
> introduce local_err and than propagate it to errp. Instead, use
> ERRP_AUTO_PROPAGATE macro, benefits are:
> 1. No need of explicit error_propagate call
> 2. No need of explicit local_err variable: use errp directly
> 3. ERRP_AUTO_PROPAGATE leaves errp as is if it's not NULL or
>     &error_fatel, this means that we don't break error_abort
>     (we'll abort on error_set, not on error_propagate)
>
> This commit (together with its neighbors) was generated by
>
> for f in $(git grep -l errp \*.[ch]); do \
>      spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
>      --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff $f; \
> done;
>
> then fix a bit of compilation problems: coccinelle for some reason
> leaves several
> f() {
>      ...
>      goto out;
>      ...
>      out:
> }
> patterns, with "out:" at function end.
>
> then
> ./python/commit-per-subsystem.py MAINTAINERS "$(< auto-msg)"
>
> (auto-msg was a file with this commit message)
>
> Still, for backporting it may be more comfortable to use only the first
> command and then do one huge commit.
>
> Reported-by: Kevin Wolf <address@hidden>
> Reported-by: Greg Kurz <address@hidden>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>   hw/core/loader-fit.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
> index 3ee9fb2f2e..84f35a1fe2 100644
> --- a/hw/core/loader-fit.c
> +++ b/hw/core/loader-fit.c
> @@ -120,6 +120,7 @@ static int fit_load_kernel(const struct fit_loader *ldr, 
> const void *itb,
>                              int cfg, void *opaque, hwaddr *pend,
>                              Error **errp)
>   {
> +    ERRP_AUTO_PROPAGATE();

This certainly looks odd and took me some time to figure it out.

Per include/qapi/error.h:

/*
 * ERRP_AUTO_PROPAGATE
 *
 * This macro is created to be the first line of a function with Error 
*errp
 * OUT parameter. It's needed only in cases where we want to use 
rror_prepend,
 * error_append_hint or dereference *errp. It's still safe (but useless) in
 * other cases.

This function indeed uses error_prepend():

    load_data = data = fit_load_image_alloc(itb, name, &img_off, &sz, 
errp);
    if (!data) {
        error_prepend(errp, "unable to load kernel image from FIT: ");
        return -EINVAL;
    }

    err = fit_image_addr(itb, img_off, "load", &load_addr, errp);
    if (err) {
        error_prepend(errp, "unable to read kernel load address from 
FIT: ");
        ret = err;
        goto out;
    }

    err = fit_image_addr(itb, img_off, "entry", &entry_addr, errp);
    if (err) {
        error_prepend(errp, "unable to read kernel entry address from 
FIT: ");
        ret = err;
        goto out;
    }

Generating the patch with more lines context would have help a bit.

Can you add a line about error_prepend() in the commit description?

>       const char *name;
>       const void *data;
>       const void *load_data;
> @@ -178,6 +179,7 @@ static int fit_load_fdt(const struct fit_loader *ldr, const 
> void *itb,
>                           int cfg, void *opaque, const void *match_data,
>                           hwaddr kernel_end, Error **errp)
>   {
> +    ERRP_AUTO_PROPAGATE();
>       const char *name;
>       const void *data;
>       const void *load_data;

Ditto:

    load_data = data = fit_load_image_alloc(itb, name, &img_off, &sz, 
errp);
    if (!data) {
        error_prepend(errp, "unable to load FDT image from FIT: ");
        return -EINVAL;
    }

    err = fit_image_addr(itb, img_off, "load", &load_addr, errp);
    if (err == -ENOENT) {
        load_addr = ROUND_UP(kernel_end, 64 * KiB) + (10 * MiB);
        error_free(*errp);
    } else if (err) {
        error_prepend(errp, "unable to read FDT load address from FIT: ");
        ret = err;
        goto out;
    }

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>