Make bpf_address_lookup() compatible with module_address_lookup()
and clear the pointer to @modbuildid together with @modname.
It is not strictly needed because __sprint_symbol() reads @modbuildid
only when @modname is set. But better be on the safe side and make
the API more safe.
Fixes: 9294523e3768 ("module: add printk formats to add module build ID to stacktraces")
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
include/linux/filter.h | 15 +++++++++++----
kernel/kallsyms.c | 4 ++--
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index f5c859b8131a..b7b95840250a 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1362,12 +1362,18 @@ struct bpf_prog *bpf_prog_ksym_find(unsigned long addr);
static inline int
bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char **modname, char *sym)
+ unsigned long *off, char **modname,
+ const unsigned char **modbuildid, char *sym)
{
int ret = __bpf_address_lookup(addr, size, off, sym);
- if (ret && modname)
- *modname = NULL;
+ if (ret) {
+ if (modname)
+ *modname = NULL;
+ if (modbuildid)
+ *modbuildid = NULL;
+ }
+
return ret;
}
@@ -1433,7 +1439,8 @@ static inline struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
static inline int
bpf_address_lookup(unsigned long addr, unsigned long *size,
- unsigned long *off, char **modname, char *sym)
+ unsigned long *off, char **modname,
+ const unsigned char **modbuildid, char *sym)
{
return 0;
}
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 9455e3bb07fc..efb12b077220 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -374,8 +374,8 @@ static int kallsyms_lookup_buildid(unsigned long addr,
ret = module_address_lookup(addr, symbolsize, offset,
modname, modbuildid, namebuf);
if (!ret)
- ret = bpf_address_lookup(addr, symbolsize,
- offset, modname, namebuf);
+ ret = bpf_address_lookup(addr, symbolsize, offset,
+ modname, modbuildid, namebuf);
if (!ret)
ret = ftrace_mod_address_lookup(addr, symbolsize,
--
2.51.1On Wed, Nov 5, 2025 at 6:24 AM Petr Mladek <pmladek@suse.com> wrote:
>
> Make bpf_address_lookup() compatible with module_address_lookup()
> and clear the pointer to @modbuildid together with @modname.
>
> It is not strictly needed because __sprint_symbol() reads @modbuildid
> only when @modname is set. But better be on the safe side and make
> the API more safe.
>
> Fixes: 9294523e3768 ("module: add printk formats to add module build ID to stacktraces")
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> ---
> include/linux/filter.h | 15 +++++++++++----
> kernel/kallsyms.c | 4 ++--
> 2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index f5c859b8131a..b7b95840250a 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -1362,12 +1362,18 @@ struct bpf_prog *bpf_prog_ksym_find(unsigned long addr);
>
> static inline int
> bpf_address_lookup(unsigned long addr, unsigned long *size,
> - unsigned long *off, char **modname, char *sym)
> + unsigned long *off, char **modname,
> + const unsigned char **modbuildid, char *sym)
> {
> int ret = __bpf_address_lookup(addr, size, off, sym);
>
> - if (ret && modname)
> - *modname = NULL;
> + if (ret) {
> + if (modname)
> + *modname = NULL;
> + if (modbuildid)
> + *modbuildid = NULL;
> + }
> +
> return ret;
> }
>
> @@ -1433,7 +1439,8 @@ static inline struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
>
> static inline int
> bpf_address_lookup(unsigned long addr, unsigned long *size,
> - unsigned long *off, char **modname, char *sym)
> + unsigned long *off, char **modname,
> + const unsigned char **modbuildid, char *sym)
> {
> return 0;
> }
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index 9455e3bb07fc..efb12b077220 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -374,8 +374,8 @@ static int kallsyms_lookup_buildid(unsigned long addr,
> ret = module_address_lookup(addr, symbolsize, offset,
> modname, modbuildid, namebuf);
> if (!ret)
> - ret = bpf_address_lookup(addr, symbolsize,
> - offset, modname, namebuf);
> + ret = bpf_address_lookup(addr, symbolsize, offset,
> + modname, modbuildid, namebuf);
The initial bpf_address_lookup() 8 years ago was trying
to copy paste args and style of kallsyms_lookup().
It was odd back then. This change is doubling down on the wrong thing.
It's really odd to pass a pointer into bpf_address_lookup()
so it zero initializes it.
bpf ksyms are in the core kernel. They're never in modules.
Just call __bpf_address_lookup() here and remove the wrapper.
On Wed 2025-11-05 18:53:23, Alexei Starovoitov wrote:
> On Wed, Nov 5, 2025 at 6:24 AM Petr Mladek <pmladek@suse.com> wrote:
> >
> > Make bpf_address_lookup() compatible with module_address_lookup()
> > and clear the pointer to @modbuildid together with @modname.
> >
> > It is not strictly needed because __sprint_symbol() reads @modbuildid
> > only when @modname is set. But better be on the safe side and make
> > the API more safe.
> >
> > Fixes: 9294523e3768 ("module: add printk formats to add module build ID to stacktraces")
> > Signed-off-by: Petr Mladek <pmladek@suse.com>
> > ---
> > include/linux/filter.h | 15 +++++++++++----
> > kernel/kallsyms.c | 4 ++--
> > 2 files changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/filter.h b/include/linux/filter.h
> > index f5c859b8131a..b7b95840250a 100644
> > --- a/include/linux/filter.h
> > +++ b/include/linux/filter.h
> > @@ -1362,12 +1362,18 @@ struct bpf_prog *bpf_prog_ksym_find(unsigned long addr);
> >
> > static inline int
> > bpf_address_lookup(unsigned long addr, unsigned long *size,
> > - unsigned long *off, char **modname, char *sym)
> > + unsigned long *off, char **modname,
> > + const unsigned char **modbuildid, char *sym)
> > {
> > int ret = __bpf_address_lookup(addr, size, off, sym);
> >
> > - if (ret && modname)
> > - *modname = NULL;
> > + if (ret) {
> > + if (modname)
> > + *modname = NULL;
> > + if (modbuildid)
> > + *modbuildid = NULL;
> > + }
> > +
> > return ret;
> > }
> >
> > @@ -1433,7 +1439,8 @@ static inline struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
> >
> > static inline int
> > bpf_address_lookup(unsigned long addr, unsigned long *size,
> > - unsigned long *off, char **modname, char *sym)
> > + unsigned long *off, char **modname,
> > + const unsigned char **modbuildid, char *sym)
> > {
> > return 0;
> > }
> > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > index 9455e3bb07fc..efb12b077220 100644
> > --- a/kernel/kallsyms.c
> > +++ b/kernel/kallsyms.c
> > @@ -374,8 +374,8 @@ static int kallsyms_lookup_buildid(unsigned long addr,
> > ret = module_address_lookup(addr, symbolsize, offset,
> > modname, modbuildid, namebuf);
> > if (!ret)
> > - ret = bpf_address_lookup(addr, symbolsize,
> > - offset, modname, namebuf);
> > + ret = bpf_address_lookup(addr, symbolsize, offset,
> > + modname, modbuildid, namebuf);
>
> The initial bpf_address_lookup() 8 years ago was trying
> to copy paste args and style of kallsyms_lookup().
> It was odd back then. This change is doubling down on the wrong thing.
> It's really odd to pass a pointer into bpf_address_lookup()
> so it zero initializes it.
> bpf ksyms are in the core kernel. They're never in modules.
> Just call __bpf_address_lookup() here and remove the wrapper.
I agree that it is ugly. It would make sense to initialize the
pointers in kallsyms_lookup_buildid and call there
__bpf_address_lookup() variant. Something like:
static int kallsyms_lookup_buildid(unsigned long addr,
unsigned long *symbolsize,
unsigned long *offset, char **modname,
const unsigned char **modbuildid, char *namebuf)
{
int ret;
if (modname)
*modname = NULL;
if (modbuildid)
*modbuildid = NULL;
namebuf[0] = 0;
[...]
if (!ret)
ret = __bpf_address_lookup(addr, symbolsize, offset, namebuf);
}
As a result bpf_address_lookup() won't have any caller.
And __bpf_address_lookup() would have two callers.
It would make sense to remove bpf_address_lookup() and
rename __bpf_address_lookup() to bpf_address_lookup().
How does that sound?
Would you prefer to do this in one patch or in two steps, please?
Best Regards,
Petr
On Fri, Nov 7, 2025 at 5:08 AM Petr Mladek <pmladek@suse.com> wrote:
>
> On Wed 2025-11-05 18:53:23, Alexei Starovoitov wrote:
> > On Wed, Nov 5, 2025 at 6:24 AM Petr Mladek <pmladek@suse.com> wrote:
> > >
> > > Make bpf_address_lookup() compatible with module_address_lookup()
> > > and clear the pointer to @modbuildid together with @modname.
> > >
> > > It is not strictly needed because __sprint_symbol() reads @modbuildid
> > > only when @modname is set. But better be on the safe side and make
> > > the API more safe.
> > >
> > > Fixes: 9294523e3768 ("module: add printk formats to add module build ID to stacktraces")
> > > Signed-off-by: Petr Mladek <pmladek@suse.com>
> > > ---
> > > include/linux/filter.h | 15 +++++++++++----
> > > kernel/kallsyms.c | 4 ++--
> > > 2 files changed, 13 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/include/linux/filter.h b/include/linux/filter.h
> > > index f5c859b8131a..b7b95840250a 100644
> > > --- a/include/linux/filter.h
> > > +++ b/include/linux/filter.h
> > > @@ -1362,12 +1362,18 @@ struct bpf_prog *bpf_prog_ksym_find(unsigned long addr);
> > >
> > > static inline int
> > > bpf_address_lookup(unsigned long addr, unsigned long *size,
> > > - unsigned long *off, char **modname, char *sym)
> > > + unsigned long *off, char **modname,
> > > + const unsigned char **modbuildid, char *sym)
> > > {
> > > int ret = __bpf_address_lookup(addr, size, off, sym);
> > >
> > > - if (ret && modname)
> > > - *modname = NULL;
> > > + if (ret) {
> > > + if (modname)
> > > + *modname = NULL;
> > > + if (modbuildid)
> > > + *modbuildid = NULL;
> > > + }
> > > +
> > > return ret;
> > > }
> > >
> > > @@ -1433,7 +1439,8 @@ static inline struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
> > >
> > > static inline int
> > > bpf_address_lookup(unsigned long addr, unsigned long *size,
> > > - unsigned long *off, char **modname, char *sym)
> > > + unsigned long *off, char **modname,
> > > + const unsigned char **modbuildid, char *sym)
> > > {
> > > return 0;
> > > }
> > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> > > index 9455e3bb07fc..efb12b077220 100644
> > > --- a/kernel/kallsyms.c
> > > +++ b/kernel/kallsyms.c
> > > @@ -374,8 +374,8 @@ static int kallsyms_lookup_buildid(unsigned long addr,
> > > ret = module_address_lookup(addr, symbolsize, offset,
> > > modname, modbuildid, namebuf);
> > > if (!ret)
> > > - ret = bpf_address_lookup(addr, symbolsize,
> > > - offset, modname, namebuf);
> > > + ret = bpf_address_lookup(addr, symbolsize, offset,
> > > + modname, modbuildid, namebuf);
> >
> > The initial bpf_address_lookup() 8 years ago was trying
> > to copy paste args and style of kallsyms_lookup().
> > It was odd back then. This change is doubling down on the wrong thing.
> > It's really odd to pass a pointer into bpf_address_lookup()
> > so it zero initializes it.
> > bpf ksyms are in the core kernel. They're never in modules.
> > Just call __bpf_address_lookup() here and remove the wrapper.
>
> I agree that it is ugly. It would make sense to initialize the
> pointers in kallsyms_lookup_buildid and call there
> __bpf_address_lookup() variant. Something like:
>
> static int kallsyms_lookup_buildid(unsigned long addr,
> unsigned long *symbolsize,
> unsigned long *offset, char **modname,
> const unsigned char **modbuildid, char *namebuf)
> {
> int ret;
>
> if (modname)
> *modname = NULL;
> if (modbuildid)
> *modbuildid = NULL;
> namebuf[0] = 0;
> [...]
> if (!ret)
> ret = __bpf_address_lookup(addr, symbolsize, offset, namebuf);
>
> }
Yes. Exactly.
> As a result bpf_address_lookup() won't have any caller.
> And __bpf_address_lookup() would have two callers.
yep
> It would make sense to remove bpf_address_lookup() and
> rename __bpf_address_lookup() to bpf_address_lookup().
yep
> How does that sound?
> Would you prefer to do this in one patch or in two steps, please?
Whichever way is easier. I think it's fine to do it in one go,
though it crosses different subsystems.
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