printk() format %pS wrong symbol

[William Tambe]

On Sat, Jul 4, 2020 at 1:15 PM Valentin Vidić
<vvidic at valentin-vidic.from.hr> wrote:
>
> On Sat, Jul 04, 2020 at 12:04:59PM -0400, William Tambe wrote:
> > How or which function within that file translates an address to the string
> > symbol+offset for the format %pS ?
>
> %pS seems to end up in here:

Thanks,
the issue I am having is due to sprint_backtrace() calling
__sprint_symbol() with its argument symbol_offset == -1.
Despite the comment above its definition, it is hard to understand why
sprint_backtrace() calls __sprint_symbol() that way; in our port it
results in printing incorrect symbols.
As a workaround, we have made sprint_backtrace() to be the same as
sprint_symbol().

>
> static int __sprint_symbol(char *buffer, unsigned long address,
>                            int symbol_offset, int add_offset)
> {
>         char *modname;
>         const char *name;
>         unsigned long offset, size;
>         int len;
>
>         address += symbol_offset;
>         name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
>         if (!name)
>                 return sprintf(buffer, "0x%lx", address - symbol_offset);
>
>         if (name != buffer)
>                 strcpy(buffer, name);
>         len = strlen(buffer);
>         offset -= symbol_offset;
>
>         if (add_offset)
>                 len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);
>
>         if (modname)
>                 len += sprintf(buffer + len, " [%s]", modname);
>
>         return len;
> }
>
> --
> Valentin
>
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