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| author | Mitchell Horne <mhorne@FreeBSD.org> | 2020-01-17 17:03:25 +0000 |
|---|---|---|
| committer | Mitchell Horne <mhorne@FreeBSD.org> | 2020-01-17 17:03:25 +0000 |
| commit | 7fdf7f9183508099458d93fb936d9bf5fc1a6061 (patch) | |
| tree | 0d20aec7f37f00e5dfa51546c12f8b71e42faba7 /sys/riscv/riscv | |
| parent | 36e33a8ef05e3a13250d3c09d5c14977fa31b0a4 (diff) | |
| download | src-7fdf7f9183508099458d93fb936d9bf5fc1a6061.tar.gz src-7fdf7f9183508099458d93fb936d9bf5fc1a6061.zip | |
RISC-V: fix global pointer assignment at boot
As part of the RISC-V ABI, the gp register is expected to initialized
with the address of __global_pointer$ as early as possible. This allows
loads and stores from .sdata to be relaxed based on the value of gp. In
locore.S we do this initialization twice, once each for va and mpva.
However, in both cases the initialization is preceded by an la
instruction, which in theory could be relaxed by the linker.
Move the initialization of gp to be slightly earlier (before la
cpu_exception_handler), and add an additional gp initialization at the
very beginning of _start, before virtual memory is set up.
Reported by: jrtc27
Reviewed by: jrtc27
Differential Revision: https://reviews.freebsd.org/D23139
Notes
Notes:
svn path=/head/; revision=356835
Diffstat (limited to 'sys/riscv/riscv')
| -rw-r--r-- | sys/riscv/riscv/locore.S | 29 |
1 files changed, 17 insertions, 12 deletions
diff --git a/sys/riscv/riscv/locore.S b/sys/riscv/riscv/locore.S index 0d4466da610c..8d3b89897c3e 100644 --- a/sys/riscv/riscv/locore.S +++ b/sys/riscv/riscv/locore.S @@ -53,6 +53,12 @@ .text .globl _start _start: + /* Set the global pointer */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop + /* Get the physical address kernel loaded to */ lla t0, virt_map ld t1, 0(t0) @@ -168,6 +174,11 @@ _start: .align 2 va: + /* Set the global pointer again, this time with the virtual address. */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop /* Setup supervisor trap vector */ la t0, cpu_exception_handler @@ -177,12 +188,6 @@ va: li t0, 0 csrw sscratch, t0 - /* Set the global pointer */ -.option push -.option norelax - la gp, __global_pointer$ -.option pop - /* Initialize stack pointer */ la s3, initstack_end mv sp, s3 @@ -322,6 +327,12 @@ ENTRY(mpentry) .align 2 mpva: + /* Set the global pointer again, this time with the virtual address. */ +.option push +.option norelax + lla gp, __global_pointer$ +.option pop + /* Setup supervisor trap vector */ la t0, cpu_exception_handler csrw stvec, t0 @@ -330,12 +341,6 @@ mpva: li t0, 0 csrw sscratch, t0 - /* Set the global pointer */ -.option push -.option norelax - la gp, __global_pointer$ -.option pop - call init_secondary END(mpentry) #endif |