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Date: Mon, 29 Jan 2024 11:26:41 -0800
From: Luis Chamberlain <mcgrof@...nel.org>
To: masahiroy@...nel.org,
deller@....de
Cc: mcgrof@...nel.org,
arnd@...db.de,
linux-arch@...r.kernel.org,
linux-modules@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] modules: Ensure 64-bit alignment on __ksymtab_* sections
From: Helge Deller <deller@....de>
On 64-bit architectures without CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
(e.g. ppc64, ppc64le, parisc, s390x,...) the __KSYM_REF() macro stores
64-bit pointers into the __ksymtab* sections.
Make sure that those sections will be correctly aligned at module link time,
otherwise unaligned memory accesses may happen at runtime.
The __kcrctab* sections store 32-bit entities, so use ALIGN(4) for those.
Testing with the kallsyms selftest on x86_64 we see a savings of about
1,958,153 ns in the worst case which may or not be within noise. Testing
on parisc would be useful and welcomed.
On x86_64 before:
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
86,430,119 ns duration_time
84,407,000 ns system_time
213 page-faults
0.086430119 seconds time elapsed
0.000000000 seconds user
0.084407000 seconds sys
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
85,777,474 ns duration_time
82,581,000 ns system_time
212 page-faults
0.085777474 seconds time elapsed
0.000000000 seconds user
0.082581000 seconds sys
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
87,906,053 ns duration_time
87,939,000 ns system_time
212 page-faults
0.087906053 seconds time elapsed
0.000000000 seconds user
0.087939000 seconds sys
After:
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
82,925,631 ns duration_time
83,000,000 ns system_time
212 page-faults
0.082925631 seconds time elapsed
0.000000000 seconds user
0.083000000 seconds sys
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
87,776,380 ns duration_time
86,678,000 ns system_time
213 page-faults
0.087776380 seconds time elapsed
0.000000000 seconds user
0.086678000 seconds sys
Performance counter stats for '/sbin/modprobe test_kallsyms_b':
85,947,900 ns duration_time
82,006,000 ns system_time
212 page-faults
0.085947900 seconds time elapsed
0.000000000 seconds user
0.082006000 seconds sys
Signed-off-by: Helge Deller <deller@....de>
[mcgrof: ran kallsyms selftests on x86_64]
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
scripts/module.lds.S | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index bf5bcf2836d8..b00415a9ff27 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -15,10 +15,10 @@ SECTIONS {
*(.discard.*)
}
- __ksymtab 0 : { *(SORT(___ksymtab+*)) }
- __ksymtab_gpl 0 : { *(SORT(___ksymtab_gpl+*)) }
- __kcrctab 0 : { *(SORT(___kcrctab+*)) }
- __kcrctab_gpl 0 : { *(SORT(___kcrctab_gpl+*)) }
+ __ksymtab 0 : ALIGN(8) { *(SORT(___ksymtab+*)) }
+ __ksymtab_gpl 0 : ALIGN(8) { *(SORT(___ksymtab_gpl+*)) }
+ __kcrctab 0 : ALIGN(4) { *(SORT(___kcrctab+*)) }
+ __kcrctab_gpl 0 : ALIGN(4) { *(SORT(___kcrctab_gpl+*)) }
.ctors 0 : ALIGN(8) { *(SORT(.ctors.*)) *(.ctors) }
.init_array 0 : ALIGN(8) { *(SORT(.init_array.*)) *(.init_array) }
--
2.42.0
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