diff options
| author | Jan Beulich <JBeulich@suse.com> | 2014-11-04 08:50:48 +0000 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2014-11-04 20:43:14 +0100 |
| commit | 97b67ae559947f1e208439a1bf6a734da3087006 (patch) | |
| tree | e0a75ea8c5eddf24755fbb1d9f30c6715c935c96 /arch/x86/kernel/vmlinux.lds.S | |
| parent | 6d24c5f72dfb26e5fa7f02fa9266dfdbae41adba (diff) | |
x86-64: Use RIP-relative addressing for most per-CPU accesses
Observing that per-CPU data (in the SMP case) is reachable by
exploiting 64-bit address wraparound (building on the default kernel
load address being at 16Mb), the one byte shorter RIP-relative
addressing form can be used for most per-CPU accesses. The one
exception are the "stable" reads, where the use of the "P" operand
modifier prevents the compiler from using RIP-relative addressing, but
is unavoidable due to the use of the "p" constraint (side note: with
gcc 4.9.x the intended effect of this isn't being achieved anymore,
see gcc bug 63637).
With the dependency on the minimum kernel load address, arbitrarily
low values for CONFIG_PHYSICAL_START are now no longer possible. A
link time assertion is being added, directing to the need to increase
that value when it triggers.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/5458A1780200007800044A9D@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/vmlinux.lds.S')
| -rw-r--r-- | arch/x86/kernel/vmlinux.lds.S | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 49edf2dd3613..00bf300fd846 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -186,6 +186,8 @@ SECTIONS * start another segment - init. */ PERCPU_VADDR(INTERNODE_CACHE_BYTES, 0, :percpu) + ASSERT(SIZEOF(.data..percpu) < CONFIG_PHYSICAL_START, + "per-CPU data too large - increase CONFIG_PHYSICAL_START") #endif INIT_TEXT_SECTION(PAGE_SIZE) |