Large modules with 6.15 [was: [PATCH v4 6/6] percpu/x86: Enable strict percpu checks via named AS qualifiers]
From: Jiri Slaby <jirislaby@kernel.org>
Date: 2025-06-05 14:27:09
Also in:
linux-arch, linux-bcachefs, linux-mm, lkml
On 27. 01. 25, 17:05, Uros Bizjak wrote:
quoted hunk ↗ jump to hunk
This patch declares percpu variables in __seg_gs/__seg_fs named AS and keeps them named AS qualified until they are dereferenced with percpu accessor. This approach enables various compiler check for cross-namespace variable assignments. Signed-off-by: Uros Bizjak <redacted> Acked-by: Nadav Amit <redacted> Cc: Dennis Zhou <dennis@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Lameter <redacted> Cc: Thomas Gleixner <redacted> Cc: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Brian Gerst <redacted> Cc: Peter Zijlstra <peterz@infradead.org> --- arch/x86/include/asm/percpu.h | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index 27f668660abe..474d648bca9a 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h@@ -95,9 +95,18 @@ #endif /* CONFIG_SMP */ -#define __my_cpu_type(var) typeof(var) __percpu_seg_override -#define __my_cpu_ptr(ptr) (__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr) -#define __my_cpu_var(var) (*__my_cpu_ptr(&(var))) +#if defined(CONFIG_USE_X86_SEG_SUPPORT) && defined(USE_TYPEOF_UNQUAL) +# define __my_cpu_type(var) typeof(var) +# define __my_cpu_ptr(ptr) (ptr) +# define __my_cpu_var(var) (var) + +# define __percpu_qual __percpu_seg_override +#else +# define __my_cpu_type(var) typeof(var) __percpu_seg_override +# define __my_cpu_ptr(ptr) (__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr) +# define __my_cpu_var(var) (*__my_cpu_ptr(&(var))) +#endif +
Another issue with this is this causes all modules in 6.15 are 2-4 times
(compressed size) bigger:
$ ll /usr/lib/modules/*-[0-9]-default/kernel/drivers/atm/atmtcp.ko.zst
> -rw-r--r--. 1 root root 10325 May 13 11:49
/usr/lib/modules/6.14.6-2-default/kernel/drivers/atm/atmtcp.ko.zst
> -rw-r--r--. 1 root root 39677 Jun 2 09:13
/usr/lib/modules/6.15.0-1-default/kernel/drivers/atm/atmtcp.ko.zst
It's due to larger .BTF section:
.BTF PROGBITS 0000000000000000 [-00003080-]
[- 00000000000011a8-] {+00003100+}
{+ 0000000000012cf8+} 0000000000000000 0 0 1
There are a lot of new BTF types defined in each module like:
+attribute_group STRUCT
+backing_dev_info STRUCT
+bdi_writeback STRUCT
+bin_attribute STRUCT
+bio_end_io_t TYPEDEF
+bio_list STRUCT
+bio_set STRUCT
+bio STRUCT
+bio_vec STRUCT
Reverting this gives me back to normal sizes.
Any ideas?
FTR downstream report:
https://bugzilla.suse.com/show_bug.cgi?id=1244135
thanks,
--
js
suse labs