[PATCH v2] RISC-V: Initialize the jvt CSR

[PATCH v2] RISC-V: Initialize the jvt CSR

[Hau Hsu]

Set symbol '__jvt_base$' as weak. So if the symbol is not set in the
linker script, the address would be 0. We initialize jvt CSR only if
the address is not 0.

Also use csr number directly instead of using symbolic name to prevent the
backward incompatible issue.

psabi reference:
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/2d770815dc9a8b11e61ea1abd487cb25ee56ad5e/riscv-elf.adoc#table-jump-relaxation
---
 libgloss/riscv/crt0.S | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libgloss/riscv/crt0.S b/libgloss/riscv/crt0.S
index 7a4e4e32c..f1c5419a5 100644
--- a/libgloss/riscv/crt0.S
+++ b/libgloss/riscv/crt0.S
@@ -26,6 +26,17 @@ _start:
   addi  gp, gp, %pcrel_lo(1b)
 .option pop
 
+  /* Initialize jvt CSR (reg addr: 0x0017) */
+  .weak __jvt_base$
+  lla a0, __jvt_base$
+  beqz a0, .Ljvt_init_end
+.option push
+.option norelax
+.option arch, +zicsr
+  csrw 0x17, a0
+.option pop
+.Ljvt_init_end:
+
   # Clear the bss segment
   la      a0, __bss_start
   la      a2, _end
-- 
2.37.1

Re: [PATCH v2] RISC-V: Initialize the jvt CSR

[Kito Cheng]

LGTM

On Fri, Jan 5, 2024 at 3:07 PM Hau Hsu <hau.hsu@sifive.com> wrote:
>
> Set symbol '__jvt_base$' as weak. So if the symbol is not set in the
> linker script, the address would be 0. We initialize jvt CSR only if
> the address is not 0.
>
> Also use csr number directly instead of using symbolic name to prevent the
> backward incompatible issue.
>
> psabi reference:
> https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/2d770815dc9a8b11e61ea1abd487cb25ee56ad5e/riscv-elf.adoc#table-jump-relaxation
> ---
>  libgloss/riscv/crt0.S | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/libgloss/riscv/crt0.S b/libgloss/riscv/crt0.S
> index 7a4e4e32c..f1c5419a5 100644
> --- a/libgloss/riscv/crt0.S
> +++ b/libgloss/riscv/crt0.S
> @@ -26,6 +26,17 @@ _start:
>    addi  gp, gp, %pcrel_lo(1b)
>  .option pop
>
> +  /* Initialize jvt CSR (reg addr: 0x0017) */
> +  .weak __jvt_base$
> +  lla a0, __jvt_base$
> +  beqz a0, .Ljvt_init_end
> +.option push
> +.option norelax
> +.option arch, +zicsr
> +  csrw 0x17, a0
> +.option pop
> +.Ljvt_init_end:
> +
>    # Clear the bss segment
>    la      a0, __bss_start
>    la      a2, _end
> --
> 2.37.1
>

Re: [PATCH v2] RISC-V: Initialize the jvt CSR

[Corinna Vinschen]

On Jan  5 15:06, Hau Hsu wrote:
> Set symbol '__jvt_base$' as weak. So if the symbol is not set in the
> linker script, the address would be 0. We initialize jvt CSR only if
> the address is not 0.
> 
> Also use csr number directly instead of using symbolic name to prevent the
> backward incompatible issue.
> 
> psabi reference:
> https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/2d770815dc9a8b11e61ea1abd487cb25ee56ad5e/riscv-elf.adoc#table-jump-relaxation
> ---
>  libgloss/riscv/crt0.S | 11 +++++++++++
>  1 file changed, 11 insertions(+)

Pushed.

Thanks,
Corinna