[coreboot-gerrit] New patch to review for coreboot: arch/riscv: Compile with -mcmodel=medany
Jonathan Neuschäfer (j.neuschaefer@gmx.net)
gerrit at coreboot.org
Fri Jun 10 20:38:07 CEST 2016
Jonathan Neuschäfer (j.neuschaefer at gmx.net) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/15148
-gerrit
commit 69d62976ab4b6b3062843e892cef07154059d403
Author: Jonathan Neuschäfer <j.neuschaefer at gmx.net>
Date: Fri Jun 10 19:35:15 2016 +0200
arch/riscv: Compile with -mcmodel=medany
In the default (medlow) code model, pointers are loaded with a lui, addi
instruction sequence:
lui a0, 0xNNNNN
addi a0, a0, 0xNNN
Since lui sign-extends bits 32-63 from bit 31 on RV64, lui/addi can't
load pointers just above 0x80000000, where RISC-V's RAM now lives.
The medany code model gets around this restriction by loading pointers
trough auipc and addi:
auipc a0, 0xNNNNN
addi a0, a0, 0xNNN
This way, any pointer within the current pc ±2G can be loaded, which is
by far sufficient for coreboot.
Change-Id: I77350d9218a687284c1337d987765553cf915a22
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer at gmx.net>
---
src/arch/riscv/Makefile.inc | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/arch/riscv/Makefile.inc b/src/arch/riscv/Makefile.inc
index 4521dcb..243fa53 100644
--- a/src/arch/riscv/Makefile.inc
+++ b/src/arch/riscv/Makefile.inc
@@ -15,7 +15,7 @@
##
################################################################################
-riscv_flags = -I$(src)/arch/riscv/
+riscv_flags = -I$(src)/arch/riscv/ -mcmodel=medany
riscv_asm_flags =
@@ -48,6 +48,9 @@ $(objcbfs)/bootblock.debug: $$(bootblock-objs)
-T $(call src-to-obj,bootblock,src/mainboard/$(MAINBOARDDIR)/memlayout.ld) --whole-archive --start-group $(filter-out %.ld,$(bootblock-objs)) \
$(LIBGCC_FILE_NAME_bootblock) --end-group $(COMPILER_RT_bootblock)
+bootblock-c-ccopts += $(riscv_flags)
+bootblock-S-ccopts += $(riscv_asm_flags)
+
endif
################################################################################
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