Re: [PATCH] compiler.h: Avoid the usage of __typeof_unqual__() when __GENKSYMS__ is defined

[Uros Bizjak]

On Sun, Apr 6, 2025 at 5:36 PM Uros Bizjak <ubiz...@gmail.com> wrote:

> > You are still seeing the warnings because __typeof_unqual__
> > is not only the issue.
> >
> > Hint:
> >
> > $ make -s KCFLAGS=-D__GENKSYMS__  arch/x86/kernel/setup_percpu.i
> > $ grep  'this_cpu_off;'  arch/x86/kernel/setup_percpu.i
>
> I see.
>
> With my workaround, this_cpu_off is declared as:
>
> extern __attribute__((section(".data..percpu" "..hot.."
> "this_cpu_off"))) __typeof__(unsigned long) this_cpu_off;
>
> while without workaround, the same variable is declared as:
>
> extern __seg_gs __attribute__((section(".data..percpu" "..hot.."
> "this_cpu_off"))) __typeof__(unsigned long) this_cpu_off;
>
> It looks that genksyms should be extended to handle (or ignore)
> __seg_gs/__seg_fs named address prefix. Somewhat surprising, because
> genksyms can process:
>
> extern __attribute__((section(".data..percpu" "..hot.."
> "const_current_task"))) __typeof__(struct task_struct * const
> __seg_gs) const_current_task
>
> without problems.
>
> I'm sorry, but I'm not able to extend genksyms with a new keyword by myself...

The following patch that handles typeof_unqual() as typeof(), and in
addition ignores __seg_gs similar to how other type qualifiers are
ignored, avoids genksyms errors.

Uros.

diff --git a/scripts/genksyms/keywords.c b/scripts/genksyms/keywords.c
index b85e0979a00c..ee1499d27061 100644
--- a/scripts/genksyms/keywords.c
+++ b/scripts/genksyms/keywords.c
@@ -17,6 +17,8 @@ static struct resword {
        { "__signed__", SIGNED_KEYW },
        { "__typeof", TYPEOF_KEYW },
        { "__typeof__", TYPEOF_KEYW },
+       { "__typeof_unqual", TYPEOF_KEYW },
+       { "__typeof_unqual__", TYPEOF_KEYW },
        { "__volatile", VOLATILE_KEYW },
        { "__volatile__", VOLATILE_KEYW },
        { "__builtin_va_list", VA_LIST_KEYW },
@@ -40,6 +42,10 @@ static struct resword {
        // KAO. },
        // { "attribute", ATTRIBUTE_KEYW },
 
+       // X86 named address space qualifiers
+       { "__seg_gs", X86_SEG_KEYW },
+       { "__seg_fs", X86_SEG_KEYW },
+
        { "auto", AUTO_KEYW },
        { "char", CHAR_KEYW },
        { "const", CONST_KEYW },
@@ -57,6 +63,7 @@ static struct resword {
        { "struct", STRUCT_KEYW },
        { "typedef", TYPEDEF_KEYW },
        { "typeof", TYPEOF_KEYW },
+       { "typeof_unqual", TYPEOF_KEYW },
        { "union", UNION_KEYW },
        { "unsigned", UNSIGNED_KEYW },
        { "void", VOID_KEYW },
diff --git a/scripts/genksyms/parse.y b/scripts/genksyms/parse.y
index ee600a804fa1..efdcf07c4eb6 100644
--- a/scripts/genksyms/parse.y
+++ b/scripts/genksyms/parse.y
@@ -91,6 +91,8 @@ static void record_compound(struct string_list **keyw,
 %token TYPEOF_KEYW
 %token VA_LIST_KEYW
 
+%token X86_SEG_KEYW
+
 %token EXPORT_SYMBOL_KEYW
 
 %token ASM_PHRASE
@@ -292,7 +294,8 @@ type_qualifier_seq:
        ;
 
 type_qualifier:
-       CONST_KEYW | VOLATILE_KEYW
+       X86_SEG_KEYW
+       | CONST_KEYW | VOLATILE_KEYW
        | RESTRICT_KEYW
                { /* restrict has no effect in prototypes so ignore it */
                  remove_node($1);