path: root/arch/parisc/include/asm/sections.h
diff options
authorHelge Deller <deller@gmx.de>2018-10-16 22:38:22 +0200
committerHelge Deller <deller@gmx.de>2018-10-17 17:22:26 +0200
commit3847dab77421867fbc77faacb2f377d44e729e1b (patch)
treeac712f1c1ee3cebd0a72f11b48a68e33a8888cd8 /arch/parisc/include/asm/sections.h
parent34c201ae49fe9e0bf3b389da5869d810f201c740 (diff)
parisc: Add alternative coding infrastructure
This patch adds the necessary code to patch a running kernel at runtime to improve performance. The current implementation offers a few optimizations variants: - When running a SMP kernel on a single UP processor, unwanted assembler statements like locking functions are overwritten with NOPs. When multiple instructions shall be skipped, one branch instruction is used instead of multiple nop instructions. - In the UP case, some pdtlb and pitlb instructions are patched to become pdtlb,l and pitlb,l which only flushes the CPU-local tlb entries instead of broadcasting the flush to other CPUs in the system and thus may improve performance. - fic and fdc instructions are skipped if no I- or D-caches are installed. This should speed up qemu emulation and cacheless systems. - If no cache coherence is needed for IO operations, the relevant fdc and sync instructions in the sba and ccio drivers are replaced by nops. - On systems which share I- and D-TLBs and thus don't have a seperate instruction TLB, the pitlb instruction is replaced by a nop. Live-patching is done early in the boot process, just after having run the system inventory. No drivers are running and thus no external interrupts should arrive. So the hope is that no TLB exceptions will occur during the patching. If this turns out to be wrong we will probably need to do the patching in real-mode. Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc/include/asm/sections.h')
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 5a40b51df80c..bb52aea0cb21 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -5,6 +5,8 @@
/* nothing to see, move along */
#include <asm-generic/sections.h>
+extern char __alt_instructions[], __alt_instructions_end[];
#ifdef CONFIG_64BIT