diff options
| author | Uros Bizjak <[email protected]> | 2023-10-15 22:24:39 +0200 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2023-10-16 12:51:58 +0200 |
| commit | a048d3abae7c33f0a3f4575fab15ac5504d443f7 (patch) | |
| tree | a6a75c6d29d408aee9a7b4f17f5228e31ca02fcd /lib/test_fortify/write_overflow-strncpy.c | |
| parent | e29aad08b1da7772b362537be32335c0394e65fe (diff) | |
x86/percpu: Rewrite arch_raw_cpu_ptr() to be easier for compilers to optimize
Implement arch_raw_cpu_ptr() as a load from this_cpu_off and then
add the ptr value to the base. This way, the compiler can propagate
addend to the following instruction and simplify address calculation.
E.g.: address calcuation in amd_pmu_enable_virt() improves from:
48 c7 c0 00 00 00 00 mov $0x0,%rax
87b7: R_X86_64_32S cpu_hw_events
65 48 03 05 00 00 00 add %gs:0x0(%rip),%rax
00
87bf: R_X86_64_PC32 this_cpu_off-0x4
48 c7 80 28 13 00 00 movq $0x0,0x1328(%rax)
00 00 00 00
to:
65 48 8b 05 00 00 00 mov %gs:0x0(%rip),%rax
00
8798: R_X86_64_PC32 this_cpu_off-0x4
48 c7 80 00 00 00 00 movq $0x0,0x0(%rax)
00 00 00 00
87a6: R_X86_64_32S cpu_hw_events+0x1328
The compiler also eliminates additional redundant loads from
this_cpu_off, reducing the number of percpu offset reads
from 1668 to 1646 on a test build, a -1.3% reduction.
Signed-off-by: Uros Bizjak <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Uros Bizjak <[email protected]>
Cc: Sean Christopherson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Diffstat (limited to 'lib/test_fortify/write_overflow-strncpy.c')
0 files changed, 0 insertions, 0 deletions