Re: [PATCH v8 1/5] xen: introduce CONFIG_GENERIC_BUG_FRAME

[Jan Beulich <jbeulich@suse.com>]

On 15.03.2023 18:21, Oleksii Kurochko wrote:
> --- /dev/null
> +++ b/xen/common/bug.c
> @@ -0,0 +1,108 @@
> +#include <xen/bug.h>
> +#include <xen/debugger.h>
> +#include <xen/errno.h>
> +#include <xen/kernel.h>
> +#include <xen/livepatch.h>
> +#include <xen/string.h>
> +#include <xen/types.h>
> +#include <xen/virtual_region.h>
> +
> +#include <asm/processor.h>

I actually meant to also ask: What is this needed for? Glancing over the
code ...

> +/*
> + * Returns a negative value in case of an error otherwise
> + * BUGFRAME_{run_fn, warn, bug, assert}
> + */
> +int do_bug_frame(struct cpu_user_regs *regs, unsigned long pc)
> +{
> +    const struct bug_frame *bug = NULL;
> +    const struct virtual_region *region;
> +    const char *prefix = "", *filename, *predicate;
> +    unsigned long fixup;
> +    unsigned int id, lineno;
> +
> +    region = find_text_region(pc);
> +    if ( !region )
> +        return -EINVAL;
> +
> +    for ( id = 0; id < BUGFRAME_NR; id++ )
> +    {
> +        const struct bug_frame *b;
> +        size_t i;
> +
> +        for ( i = 0, b = region->frame[id].bugs;
> +              i < region->frame[id].n_bugs; b++, i++ )
> +        {
> +            if ( bug_loc(b) == pc )
> +            {
> +                bug = b;
> +                goto found;
> +            }
> +        }
> +    }
> +
> + found:
> +    if ( !bug )
> +        return -ENOENT;
> +
> +    if ( id == BUGFRAME_run_fn )
> +    {
> +        void (*fn)(struct cpu_user_regs *) = bug_ptr(bug);
> +
> +        fn(regs);
> +
> +        /* Re-enforce consistent types, because of the casts involved. */
> +        if ( false )
> +            run_in_exception_handler(fn);
> +
> +        return id;
> +    }
> +
> +    /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
> +    filename = bug_ptr(bug);
> +    if ( !is_kernel(filename) && !is_patch(filename) )
> +        return -EINVAL;
> +    fixup = strlen(filename);
> +    if ( fixup > 50 )
> +    {
> +        filename += fixup - 47;
> +        prefix = "...";
> +    }
> +    lineno = bug_line(bug);
> +
> +    switch ( id )
> +    {
> +    case BUGFRAME_warn:
> +        printk("Xen WARN at %s%s:%d\n", prefix, filename, lineno);
> +        show_execution_state(regs);
> +
> +        break;
> +
> +    case BUGFRAME_bug:
> +        printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
> +
> +        if ( BUG_DEBUGGER_TRAP_FATAL(regs) )
> +            break;
> +
> +        show_execution_state(regs);
> +        panic("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
> +
> +    case BUGFRAME_assert:
> +        /* ASSERT: decode the predicate string pointer. */
> +        predicate = bug_msg(bug);
> +        if ( !is_kernel(predicate) && !is_patch(predicate) )
> +            predicate = "<unknown>";
> +
> +        printk("Assertion '%s' failed at %s%s:%d\n",
> +               predicate, prefix, filename, lineno);
> +
> +        if ( BUG_DEBUGGER_TRAP_FATAL(regs) )
> +            break;
> +
> +        show_execution_state(regs);
> +        panic("Assertion '%s' failed at %s%s:%d\n",
> +              predicate, prefix, filename, lineno);
> +    }
> +
> +    return id;
> +}

... I can't really spot what it might be that comes from that header.
Oh, on the N+1st run I've spotted it - it's show_execution_state().
The declaration of which, already being used from common code ahead
of this series, should imo be moved to a common header. I guess I'll
make yet another patch ...

Jan