* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 7:07 [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Ard Biesheuvel
@ 2025-03-20 8:22 ` Ard Biesheuvel
2025-03-20 9:01 ` [tip: x86/core] gendwarfksyms: Define __GENKSYMS__ when processing <asm/asm-protoypes.h> tip-bot2 for Ard Biesheuvel
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Ard Biesheuvel @ 2025-03-20 8:22 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-kbuild, brgerst, x86, masahiroy, nathan, linux-kernel,
nogikh, Sami Tolvanen, syzbot+06fd1a3613c50d36129e
On Thu, 20 Mar 2025 at 08:08, Ard Biesheuvel <ardb+git@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> through the compiler to capture the exported symbols. This ensures that
> exported symbols such as __ref_stack_chk_guard on x86, which is declared
> conditionally, is visible to the tool.
>
> Otherwise, an error such as the below may be raised, breaking the build
> when CONFIG_GENDWARFKSYMS=y
>
> <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
https://syzkaller.appspot.com/bug?extid=06fd1a3613c50d36129e
> ---
> scripts/Makefile.build | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 993708d11874..7855cdc4e763 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> getasmexports = \
> { echo "\#include <linux/kernel.h>" ; \
> echo "\#include <linux/string.h>" ; \
> + echo "\#define __GENKSYMS__" ; \
> echo "\#include <asm/asm-prototypes.h>" ; \
> $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
>
> --
> 2.49.0.rc1.451.g8f38331e32-goog
>
^ permalink raw reply [flat|nested] 10+ messages in thread* [tip: x86/core] gendwarfksyms: Define __GENKSYMS__ when processing <asm/asm-protoypes.h>
2025-03-20 7:07 [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Ard Biesheuvel
2025-03-20 8:22 ` Ard Biesheuvel
@ 2025-03-20 9:01 ` tip-bot2 for Ard Biesheuvel
2025-03-20 14:40 ` [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Masahiro Yamada
2025-03-20 14:47 ` Sami Tolvanen
3 siblings, 0 replies; 10+ messages in thread
From: tip-bot2 for Ard Biesheuvel @ 2025-03-20 9:01 UTC (permalink / raw)
To: linux-tip-commits
Cc: syzbot+06fd1a3613c50d36129e, Ard Biesheuvel, Ingo Molnar,
Masahiro Yamada, Michal Marek, Brian Gerst, Uros Bizjak,
H. Peter Anvin, x86, linux-kernel
The following commit has been merged into the x86/core branch of tip:
Commit-ID: fb3135208f688c5cab7d05e3a0d229935ee7611a
Gitweb: https://git.kernel.org/tip/fb3135208f688c5cab7d05e3a0d229935ee7611a
Author: Ard Biesheuvel <ardb@kernel.org>
AuthorDate: Thu, 20 Mar 2025 08:07:47 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 20 Mar 2025 09:48:49 +01:00
gendwarfksyms: Define __GENKSYMS__ when processing <asm/asm-protoypes.h>
Ensure that __GENKSYMS__ is #define'd when passing <asm/asm-prototypes.h>
through the compiler to capture the exported symbols. This ensures that
exported symbols such as __ref_stack_chk_guard on x86, which is declared
conditionally, is visible to the tool.
Otherwise the build might break when CONFIG_GENDWARFKSYMS=y:
<stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250320070746.101552-2-ardb+git@google.com
---
scripts/Makefile.build | 1 +
1 file changed, 1 insertion(+)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 993708d..7855cdc 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
getasmexports = \
{ echo "\#include <linux/kernel.h>" ; \
echo "\#include <linux/string.h>" ; \
+ echo "\#define __GENKSYMS__" ; \
echo "\#include <asm/asm-prototypes.h>" ; \
$(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 7:07 [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Ard Biesheuvel
2025-03-20 8:22 ` Ard Biesheuvel
2025-03-20 9:01 ` [tip: x86/core] gendwarfksyms: Define __GENKSYMS__ when processing <asm/asm-protoypes.h> tip-bot2 for Ard Biesheuvel
@ 2025-03-20 14:40 ` Masahiro Yamada
2025-03-20 14:45 ` Ard Biesheuvel
2025-03-20 14:47 ` Sami Tolvanen
3 siblings, 1 reply; 10+ messages in thread
From: Masahiro Yamada @ 2025-03-20 14:40 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-kbuild, brgerst, x86, nathan, linux-kernel, nogikh,
Ard Biesheuvel, Sami Tolvanen, syzbot+06fd1a3613c50d36129e
On Thu, Mar 20, 2025 at 4:08 PM Ard Biesheuvel <ardb+git@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> through the compiler to capture the exported symbols. This ensures that
> exported symbols such as __ref_stack_chk_guard on x86, which is declared
> conditionally, is visible to the tool.
Why don't you make it unconditional, then?
diff --git a/arch/x86/include/asm/asm-prototypes.h
b/arch/x86/include/asm/asm-prototypes.h
index 3674006e3974..9fc6f2be663c 100644
--- a/arch/x86/include/asm/asm-prototypes.h
+++ b/arch/x86/include/asm/asm-prototypes.h
@@ -20,6 +20,4 @@
extern void cmpxchg8b_emu(void);
#endif
-#if defined(__GENKSYMS__) && defined(CONFIG_STACKPROTECTOR)
extern unsigned long __ref_stack_chk_guard;
-#endif
>
> Otherwise, an error such as the below may be raised, breaking the build
> when CONFIG_GENDWARFKSYMS=y
>
> <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> scripts/Makefile.build | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 993708d11874..7855cdc4e763 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> getasmexports = \
> { echo "\#include <linux/kernel.h>" ; \
> echo "\#include <linux/string.h>" ; \
> + echo "\#define __GENKSYMS__" ; \
> echo "\#include <asm/asm-prototypes.h>" ; \
> $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
>
> --
> 2.49.0.rc1.451.g8f38331e32-goog
>
--
Best Regards
Masahiro Yamada
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 14:40 ` [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Masahiro Yamada
@ 2025-03-20 14:45 ` Ard Biesheuvel
0 siblings, 0 replies; 10+ messages in thread
From: Ard Biesheuvel @ 2025-03-20 14:45 UTC (permalink / raw)
To: Masahiro Yamada
Cc: Ard Biesheuvel, linux-kbuild, brgerst, x86, nathan, linux-kernel,
nogikh, Sami Tolvanen, syzbot+06fd1a3613c50d36129e
On Thu, 20 Mar 2025 at 15:40, Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Thu, Mar 20, 2025 at 4:08 PM Ard Biesheuvel <ardb+git@google.com> wrote:
> >
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> > through the compiler to capture the exported symbols. This ensures that
> > exported symbols such as __ref_stack_chk_guard on x86, which is declared
> > conditionally, is visible to the tool.
>
>
> Why don't you make it unconditional, then?
>
Because this symbol is being hidden from the compiler.
Commit 577c134d311b9b has the details.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 7:07 [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Ard Biesheuvel
` (2 preceding siblings ...)
2025-03-20 14:40 ` [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h Masahiro Yamada
@ 2025-03-20 14:47 ` Sami Tolvanen
2025-03-20 16:08 ` Ard Biesheuvel
3 siblings, 1 reply; 10+ messages in thread
From: Sami Tolvanen @ 2025-03-20 14:47 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-kbuild, brgerst, x86, masahiroy, nathan, linux-kernel,
nogikh, Ard Biesheuvel, syzbot+06fd1a3613c50d36129e
Hi Ard,
On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> through the compiler to capture the exported symbols. This ensures that
> exported symbols such as __ref_stack_chk_guard on x86, which is declared
> conditionally, is visible to the tool.
>
> Otherwise, an error such as the below may be raised, breaking the build
> when CONFIG_GENDWARFKSYMS=y
>
> <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> scripts/Makefile.build | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 993708d11874..7855cdc4e763 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> getasmexports = \
> { echo "\#include <linux/kernel.h>" ; \
> echo "\#include <linux/string.h>" ; \
> + echo "\#define __GENKSYMS__" ; \
> echo "\#include <asm/asm-prototypes.h>" ; \
> $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
This works with gendwarfksyms since __GENKSYMS__ is defined after the
EXPORT_SYMBOL() definition, but I'm now getting warnings with
genksyms:
AS arch/x86/lib/clear_page_64.o
<stdin>:3:10: warning: "__GENKSYMS__" redefined
<command-line>: note: this is the location of the previous definition
Sami
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 14:47 ` Sami Tolvanen
@ 2025-03-20 16:08 ` Ard Biesheuvel
2025-03-20 16:22 ` Sami Tolvanen
0 siblings, 1 reply; 10+ messages in thread
From: Ard Biesheuvel @ 2025-03-20 16:08 UTC (permalink / raw)
To: Sami Tolvanen
Cc: Ard Biesheuvel, linux-kbuild, brgerst, x86, masahiroy, nathan,
linux-kernel, nogikh, syzbot+06fd1a3613c50d36129e
On Thu, 20 Mar 2025 at 15:48, Sami Tolvanen <samitolvanen@google.com> wrote:
>
> Hi Ard,
>
> On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@google.com> wrote:
> >
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> > through the compiler to capture the exported symbols. This ensures that
> > exported symbols such as __ref_stack_chk_guard on x86, which is declared
> > conditionally, is visible to the tool.
> >
> > Otherwise, an error such as the below may be raised, breaking the build
> > when CONFIG_GENDWARFKSYMS=y
> >
> > <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
> >
> > Cc: Sami Tolvanen <samitolvanen@google.com>
> > Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > scripts/Makefile.build | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 993708d11874..7855cdc4e763 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> > getasmexports = \
> > { echo "\#include <linux/kernel.h>" ; \
> > echo "\#include <linux/string.h>" ; \
> > + echo "\#define __GENKSYMS__" ; \
> > echo "\#include <asm/asm-prototypes.h>" ; \
> > $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
>
> This works with gendwarfksyms since __GENKSYMS__ is defined after the
> EXPORT_SYMBOL() definition, but I'm now getting warnings with
> genksyms:
>
> AS arch/x86/lib/clear_page_64.o
> <stdin>:3:10: warning: "__GENKSYMS__" redefined
> <command-line>: note: this is the location of the previous definition
>
Oops.
Do you think the fix below should be sufficient?
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -314,7 +314,7 @@
else
cmd_gensymtypes_S = \
$(getasmexports) | \
- $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+ $(CPP) $(c_flags) -xc - | $(genksyms)
endif # CONFIG_GENDWARFKSYMS
quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 16:08 ` Ard Biesheuvel
@ 2025-03-20 16:22 ` Sami Tolvanen
2025-03-20 16:41 ` Ard Biesheuvel
0 siblings, 1 reply; 10+ messages in thread
From: Sami Tolvanen @ 2025-03-20 16:22 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: Ard Biesheuvel, linux-kbuild, brgerst, x86, masahiroy, nathan,
linux-kernel, nogikh, syzbot+06fd1a3613c50d36129e
On Thu, Mar 20, 2025 at 9:09 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Thu, 20 Mar 2025 at 15:48, Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > Hi Ard,
> >
> > On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@google.com> wrote:
> > >
> > > From: Ard Biesheuvel <ardb@kernel.org>
> > >
> > > Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> > > through the compiler to capture the exported symbols. This ensures that
> > > exported symbols such as __ref_stack_chk_guard on x86, which is declared
> > > conditionally, is visible to the tool.
> > >
> > > Otherwise, an error such as the below may be raised, breaking the build
> > > when CONFIG_GENDWARFKSYMS=y
> > >
> > > <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
> > >
> > > Cc: Sami Tolvanen <samitolvanen@google.com>
> > > Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > > scripts/Makefile.build | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > index 993708d11874..7855cdc4e763 100644
> > > --- a/scripts/Makefile.build
> > > +++ b/scripts/Makefile.build
> > > @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> > > getasmexports = \
> > > { echo "\#include <linux/kernel.h>" ; \
> > > echo "\#include <linux/string.h>" ; \
> > > + echo "\#define __GENKSYMS__" ; \
> > > echo "\#include <asm/asm-prototypes.h>" ; \
> > > $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
> >
> > This works with gendwarfksyms since __GENKSYMS__ is defined after the
> > EXPORT_SYMBOL() definition, but I'm now getting warnings with
> > genksyms:
> >
> > AS arch/x86/lib/clear_page_64.o
> > <stdin>:3:10: warning: "__GENKSYMS__" redefined
> > <command-line>: note: this is the location of the previous definition
> >
>
> Oops.
>
> Do you think the fix below should be sufficient?
>
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -314,7 +314,7 @@
> else
> cmd_gensymtypes_S = \
> $(getasmexports) | \
> - $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
> + $(CPP) $(c_flags) -xc - | $(genksyms)
> endif # CONFIG_GENDWARFKSYMS
>
> quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
EXPORT_SYMBOL() has a different definition when __GENKSYMS__ is
defined, so I think with genksyms we actually do need this on the
command line. I suppose you could wrap the getasmexports definition in
#ifndef __GENKSYMS__ to avoid the warning, or just use
__GENDWARFKSYMS__ like you suggested earlier.
Sami
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 16:22 ` Sami Tolvanen
@ 2025-03-20 16:41 ` Ard Biesheuvel
2025-03-20 20:00 ` Ingo Molnar
0 siblings, 1 reply; 10+ messages in thread
From: Ard Biesheuvel @ 2025-03-20 16:41 UTC (permalink / raw)
To: Sami Tolvanen, Ingo Molnar
Cc: Ard Biesheuvel, linux-kbuild, brgerst, x86, masahiroy, nathan,
linux-kernel, nogikh, syzbot+06fd1a3613c50d36129e
On Thu, 20 Mar 2025 at 17:22, Sami Tolvanen <samitolvanen@google.com> wrote:
>
> On Thu, Mar 20, 2025 at 9:09 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > On Thu, 20 Mar 2025 at 15:48, Sami Tolvanen <samitolvanen@google.com> wrote:
> > >
> > > Hi Ard,
> > >
> > > On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@google.com> wrote:
> > > >
> > > > From: Ard Biesheuvel <ardb@kernel.org>
> > > >
> > > > Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> > > > through the compiler to capture the exported symbols. This ensures that
> > > > exported symbols such as __ref_stack_chk_guard on x86, which is declared
> > > > conditionally, is visible to the tool.
> > > >
> > > > Otherwise, an error such as the below may be raised, breaking the build
> > > > when CONFIG_GENDWARFKSYMS=y
> > > >
> > > > <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
> > > >
> > > > Cc: Sami Tolvanen <samitolvanen@google.com>
> > > > Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > > ---
> > > > scripts/Makefile.build | 1 +
> > > > 1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > > index 993708d11874..7855cdc4e763 100644
> > > > --- a/scripts/Makefile.build
> > > > +++ b/scripts/Makefile.build
> > > > @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> > > > getasmexports = \
> > > > { echo "\#include <linux/kernel.h>" ; \
> > > > echo "\#include <linux/string.h>" ; \
> > > > + echo "\#define __GENKSYMS__" ; \
> > > > echo "\#include <asm/asm-prototypes.h>" ; \
> > > > $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
> > >
> > > This works with gendwarfksyms since __GENKSYMS__ is defined after the
> > > EXPORT_SYMBOL() definition, but I'm now getting warnings with
> > > genksyms:
> > >
> > > AS arch/x86/lib/clear_page_64.o
> > > <stdin>:3:10: warning: "__GENKSYMS__" redefined
> > > <command-line>: note: this is the location of the previous definition
> > >
> >
> > Oops.
> >
> > Do you think the fix below should be sufficient?
> >
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -314,7 +314,7 @@
> > else
> > cmd_gensymtypes_S = \
> > $(getasmexports) | \
> > - $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
> > + $(CPP) $(c_flags) -xc - | $(genksyms)
> > endif # CONFIG_GENDWARFKSYMS
> >
> > quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
>
> EXPORT_SYMBOL() has a different definition when __GENKSYMS__ is
> defined, so I think with genksyms we actually do need this on the
> command line. I suppose you could wrap the getasmexports definition in
> #ifndef __GENKSYMS__ to avoid the warning, or just use
> __GENDWARFKSYMS__ like you suggested earlier.
>
Yeah, on second thought, we could just do what Masahiro suggested, and
drop the conditional from asm/asm-prototypes.h
The issue in question only affects definitions, not declarations, and
so having the declaration visible shouldn't be a problem.
Ingo, mind dropping this patch again? We'll do the below instead (I'll
send out the patch in a minute)
--- a/arch/x86/include/asm/asm-prototypes.h
+++ b/arch/x86/include/asm/asm-prototypes.h
@@ -20,6 +20,6 @@
extern void cmpxchg8b_emu(void);
#endif
-#if defined(__GENKSYMS__) && defined(CONFIG_STACKPROTECTOR)
+#ifdef CONFIG_STACKPROTECTOR
extern unsigned long __ref_stack_chk_guard;
#endif
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] gendwarfksyms: define __GENKSYMS__ when processing asm-protoypes.h
2025-03-20 16:41 ` Ard Biesheuvel
@ 2025-03-20 20:00 ` Ingo Molnar
0 siblings, 0 replies; 10+ messages in thread
From: Ingo Molnar @ 2025-03-20 20:00 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: Sami Tolvanen, Ard Biesheuvel, linux-kbuild, brgerst, x86,
masahiroy, nathan, linux-kernel, nogikh,
syzbot+06fd1a3613c50d36129e
* Ard Biesheuvel <ardb@kernel.org> wrote:
> On Thu, 20 Mar 2025 at 17:22, Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > On Thu, Mar 20, 2025 at 9:09 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> > >
> > > On Thu, 20 Mar 2025 at 15:48, Sami Tolvanen <samitolvanen@google.com> wrote:
> > > >
> > > > Hi Ard,
> > > >
> > > > On Thu, Mar 20, 2025 at 12:07 AM Ard Biesheuvel <ardb+git@google.com> wrote:
> > > > >
> > > > > From: Ard Biesheuvel <ardb@kernel.org>
> > > > >
> > > > > Ensure that __GENKSYMS__ is #define'd when passing asm/asm-prototypes.h
> > > > > through the compiler to capture the exported symbols. This ensures that
> > > > > exported symbols such as __ref_stack_chk_guard on x86, which is declared
> > > > > conditionally, is visible to the tool.
> > > > >
> > > > > Otherwise, an error such as the below may be raised, breaking the build
> > > > > when CONFIG_GENDWARFKSYMS=y
> > > > >
> > > > > <stdin>:4:15: error: use of undeclared identifier '__ref_stack_chk_guard'
> > > > >
> > > > > Cc: Sami Tolvanen <samitolvanen@google.com>
> > > > > Reported-by: syzbot+06fd1a3613c50d36129e@syzkaller.appspotmail.com
> > > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > > > ---
> > > > > scripts/Makefile.build | 1 +
> > > > > 1 file changed, 1 insertion(+)
> > > > >
> > > > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > > > index 993708d11874..7855cdc4e763 100644
> > > > > --- a/scripts/Makefile.build
> > > > > +++ b/scripts/Makefile.build
> > > > > @@ -305,6 +305,7 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
> > > > > getasmexports = \
> > > > > { echo "\#include <linux/kernel.h>" ; \
> > > > > echo "\#include <linux/string.h>" ; \
> > > > > + echo "\#define __GENKSYMS__" ; \
> > > > > echo "\#include <asm/asm-prototypes.h>" ; \
> > > > > $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
> > > >
> > > > This works with gendwarfksyms since __GENKSYMS__ is defined after the
> > > > EXPORT_SYMBOL() definition, but I'm now getting warnings with
> > > > genksyms:
> > > >
> > > > AS arch/x86/lib/clear_page_64.o
> > > > <stdin>:3:10: warning: "__GENKSYMS__" redefined
> > > > <command-line>: note: this is the location of the previous definition
> > > >
> > >
> > > Oops.
> > >
> > > Do you think the fix below should be sufficient?
> > >
> > > --- a/scripts/Makefile.build
> > > +++ b/scripts/Makefile.build
> > > @@ -314,7 +314,7 @@
> > > else
> > > cmd_gensymtypes_S = \
> > > $(getasmexports) | \
> > > - $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
> > > + $(CPP) $(c_flags) -xc - | $(genksyms)
> > > endif # CONFIG_GENDWARFKSYMS
> > >
> > > quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
> >
> > EXPORT_SYMBOL() has a different definition when __GENKSYMS__ is
> > defined, so I think with genksyms we actually do need this on the
> > command line. I suppose you could wrap the getasmexports definition in
> > #ifndef __GENKSYMS__ to avoid the warning, or just use
> > __GENDWARFKSYMS__ like you suggested earlier.
> >
>
> Yeah, on second thought, we could just do what Masahiro suggested, and
> drop the conditional from asm/asm-prototypes.h
>
> The issue in question only affects definitions, not declarations, and
> so having the declaration visible shouldn't be a problem.
>
> Ingo, mind dropping this patch again? We'll do the below instead (I'll
> send out the patch in a minute)
Yeah, done & thanks!
Ingo
^ permalink raw reply [flat|nested] 10+ messages in thread