Re: [PATCH 4/6] x86_64/entry: Mark all syscalls __noendbr

[Peter Zijlstra]

On Mon, Nov 02, 2026 at 05:06:30PM +0000, David Laight wrote:
> > --- a/tools/objtool/check.c
> > +++ b/tools/objtool/check.c
> > @@ -4672,8 +4672,15 @@ static int validate_ibt(struct objtool_f
> >  		    !strcmp(sec->name, "__patchable_function_entries"))
> >  			continue;
> >  
> > -		for_each_reloc(sec->rsec, reloc)
> > +		for_each_reloc(sec->rsec, reloc) {
> > +			struct symbol *sym = find_symbol_containing(reloc->sec->base,
> > +								    reloc_offset(reloc));
> > +
> > +			if (sym && !strcmp(sym->name, "sys_call_table"))
> > +				continue;
> 
> Does that slow things down somewhat?
> Could you do it the other way around??
> So remember the bounds of sys_call_table and just check whether the relocation
> in inside it.


--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4676,7 +4676,7 @@ static int validate_ibt(struct objtool_f
 			struct symbol *sym = find_symbol_containing(reloc->sec->base,
 								    reloc_offset(reloc));
 
-			if (sym && !strcmp(sym->name, "sys_call_table"))
+			if (sym && sym->syscall)
 				continue;
 
 			warnings += validate_ibt_data_reloc(file, reloc);
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -556,6 +556,9 @@ static int elf_add_symbol(struct elf *el
 	if (strstarts(sym->name, ".klp.sym"))
 		sym->klp = 1;
 
+	if (!strcmp(sym->name, "sys_call_table"))
+		sym->syscall = 1;
+
 	if (!sym->klp && !is_sec_sym(sym) && strstr(sym->name, ".cold")) {
 		sym->cold = 1;
 
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -85,7 +85,7 @@ struct symbol {
 	u8 fentry            : 1;
 	u8 profiling_func    : 1;
 	u8 warned	     : 1;
-	u8 embedded_insn     : 1;
+	u8 embedded_insn     : 1; //  8
 	u8 local_label       : 1;
 	u8 frame_pointer     : 1;
 	u8 ignore	     : 1;
@@ -93,11 +93,12 @@ struct symbol {
 	u8 cold		     : 1;
 	u8 prefix	     : 1;
 	u8 debug_checksum    : 1;
-	u8 changed	     : 1;
+	u8 changed	     : 1; // 16
 	u8 included	     : 1;
 	u8 klp		     : 1;
 	u8 dont_correlate    : 1;
 	u8 fake		     : 1;
+	u8 syscall           : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;