Re: [PATCH v2 29/62] objtool: Mark prefix functions

[Josh Poimboeuf]

On Wed, Jun 04, 2025 at 05:04:33PM -0700, Josh Poimboeuf wrote:
> On Mon, May 26, 2025 at 12:43:55PM +0200, Peter Zijlstra wrote:
> > > +++ b/tools/objtool/elf.c
> > > @@ -442,6 +442,11 @@ static void elf_add_symbol(struct elf *elf, struct 
> > > symbol *sym)
> > >   elf_hash_add(symbol, &sym->hash, sym->idx);
> > >   elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
> > >  
> > > + if (is_func_sym(sym) && sym->len == 16 &&
> > 
> > Where did that 'sym->len == 16' thing come from? I mean, they are, but
> > the old code didn't assert that.
> > 
> > I would rather objtool issue a warn if not 16, but still consider these
> > as prefix.
> 
> Ok:

Turns out there are kCFI cases with prefixes != 16, so I omitted the
size check altogether.

-- 
Josh

Re: [PATCH v2 29/62] objtool: Mark prefix functions

[Josh Poimboeuf]

On Mon, May 26, 2025 at 12:43:55PM +0200, Peter Zijlstra wrote:
> > +++ b/tools/objtool/elf.c
> > @@ -442,6 +442,11 @@ static void elf_add_symbol(struct elf *elf, struct 
> > symbol *sym)
> > elf_hash_add(symbol, &sym->hash, sym->idx);
> > elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
> >  
> > +   if (is_func_sym(sym) && sym->len == 16 &&
> 
> Where did that 'sym->len == 16' thing come from? I mean, they are, but
> the old code didn't assert that.
> 
> I would rather objtool issue a warn if not 16, but still consider these
> as prefix.

Ok:

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 9a1fc0392b7f..2953aa8d2b81 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -442,10 +442,12 @@ static void elf_add_symbol(struct elf *elf, struct symbol 
*sym)
elf_hash_add(symbol, &sym->hash, sym->idx);
elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
 
-   if (is_func_sym(sym) && sym->len == 16 &&
-   (strstarts(sym->name, "__pfx") || strstarts(sym->name, "__cfi_")))
+   if (is_func_sym(sym) &&
+   (strstarts(sym->name, "__pfx_") || strstarts(sym->name, "__cfi_"))) 
{
+   if (sym->len != 16)
+   WARN("%s size %d != 16", sym->name, sym->len);
sym->prefix = 1;
-
+   }
 
if (is_func_sym(sym) && strstr(sym->name, ".cold"))
sym->cold = 1;

Re: [PATCH v2 29/62] objtool: Mark prefix functions

[Peter Zijlstra]

On Fri, May 09, 2025 at 01:16:53PM -0700, Josh Poimboeuf wrote:
> In preparation for the objtool klp diff subcommand, introduce a flag to
> identify __pfx_*() and __cfi_*() functions in advance so they don't need
> to be manually identified every time a check is needed.
> 
> Signed-off-by: Josh Poimboeuf 
> ---
>  tools/objtool/check.c   | 3 +--
>  tools/objtool/elf.c | 5 +
>  tools/objtool/include/objtool/elf.h | 6 ++
>  3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index a2a025ec57e8..6b2e57d9aaf8 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -3601,8 +3601,7 @@ static int validate_branch(struct objtool_file *file, 
> struct symbol *func,
>  
>   if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
>   /* Ignore KCFI type preambles, which always fall 
> through */
> - if (!strncmp(func->name, "__cfi_", 6) ||
> - !strncmp(func->name, "__pfx_", 6))
> + if (is_prefix_func(func))
>   return 0;
>  
>   if (file->ignore_unreachables)
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index 59568381486c..9a1fc0392b7f 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -442,6 +442,11 @@ static void elf_add_symbol(struct elf *elf, struct 
> symbol *sym)
>   elf_hash_add(symbol, &sym->hash, sym->idx);
>   elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
>  
> + if (is_func_sym(sym) && sym->len == 16 &&

Where did that 'sym->len == 16' thing come from? I mean, they are, but
the old code didn't assert that.

I would rather objtool issue a warn if not 16, but still consider these
as prefix.

> + (strstarts(sym->name, "__pfx") || strstarts(sym->name, "__cfi_")))
> + sym->prefix = 1;
> +
> +
>   if (is_func_sym(sym) && strstr(sym->name, ".cold"))
>   sym->cold = 1;
>   sym->pfunc = sym->cfunc = sym;