Hi Lukas,
On Wed, Oct 31, 2018 at 11:01 PM Auer, Lukas lukas.auer@aisec.fraunhofer.de wrote:
Hi Bin,
On Wed, 2018-10-31 at 10:13 +0800, Bin Meng wrote:
Hi Lukas,
On Tue, Oct 30, 2018 at 8:57 PM Lukas Auer lukas.auer@aisec.fraunhofer.de wrote:
RISC-V has two code models, medium low (medlow) and medium any (medany). Medlow limits addressable memory to a single 2 GiB range between the absolute addresses -2 GiB and +2 GiB. Medany limits addressable memory to any single 2 GiB address range. By default, medlow is selected on 32-bit systems and medany on 64- bit systems. This matches the configuration in Linux.
The -mcmodel compiler flag is selected according to the Kconfig configuration.
Signed-off-by: Lukas Auer lukas.auer@aisec.fraunhofer.de
Changes in v2:
- Change ISA string construction, as suggested by Bin Meng
arch/riscv/Kconfig | 19 +++++++++++++++++++ arch/riscv/Makefile | 9 ++++++++- 2 files changed, 27 insertions(+), 1 deletion(-)
I had a further look at this, and I suspect we should stick to medlow for U-Boot, even for 64-bit. As U-Boot will be only running within the low 4GB memory space even for 64-bit. Adding medany seems unnecessary.
Regards, Bin
You are right, however I think it's actually because U-Boot is compiled as a position independent binary. U-Boot can be relocated above what's addressable with 32-bit if the memory is large enough. This should cause issues with medlow. I suspects that's the reason, but I am not entirely sure. What do you think?
Sorry I missed this email. I just found in your v3 this patch was dropped. I think this is still needed to explicitly pass the code model to the compiler. I believe we only need change to:
+choice + prompt "Code Model" + default CMODEL_MEDLOW
I can include the modified patch in my upcoming series.
Regards, Bin