From cb608840b3a93fb7d2409012b8845b4d1c3fa91d Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Sun, 16 Jul 2023 17:50:57 +0200 Subject: [klibc] riscv64: Move shared library below executables MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The default base address for riscv64 executables is 64 kiB, and I originally selected a base address for the shared library of 2 MiB. This limits the size of executables using it to be < 2 MiB, and it also interacts with a bug in QEMU's user-mode emulation, causing executables to immediately crash. It doesn't help code generation, because single-instruction jumps have a range of only ±1 MiB and two-instruction jumps have a range of ±2 GiB. Move the shared library to 64 kiB and executables to 576 kiB, to allow for generation of single-instruction jumps. (klibc.so is currently much smaller than the 512 kiB this allows for.) References: https://bugs.debian.org/1040981 Signed-off-by: Ben Hutchings --- usr/klibc/arch/riscv64/MCONFIG | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/usr/klibc/arch/riscv64/MCONFIG b/usr/klibc/arch/riscv64/MCONFIG index 340610861c9e5..717aedaadea81 100644 --- a/usr/klibc/arch/riscv64/MCONFIG +++ b/usr/klibc/arch/riscv64/MCONFIG @@ -13,8 +13,13 @@ KLIBCOPTFLAGS += -g endif KLIBCBITSIZE = 64 -# Normal binaries start at 64 KB, so start the libary at 2 MB. -KLIBCSHAREDFLAGS = $(LD_IMAGE_BASE_OPT) 0x00200000 +# Normal binaries start at 64 kiB. Jumps can use either a single +# instruction with offset of ±1 MiB, or two instructions with offset +# of ±2 GiB. Putting klibc.so close above the executable can cause +# breakage, so instead swap them around: klibc.so at 64 kiB and +# executable at 576 kiB. +KLIBCLDFLAGS = $(LD_IMAGE_BASE_OPT) 0x90000 +KLIBCSHAREDFLAGS = $(LD_IMAGE_BASE_OPT) 0x10000 KLIBCSHAREDFLAGS += --defsym '__global_pointer$$=0' # Kernel has never used stack trampolines -- cgit 1.2.3-korg