diff options
| author | Mitchell Horne <mhorne@FreeBSD.org> | 2024-06-03 17:24:12 +0000 |
|---|---|---|
| committer | Mitchell Horne <mhorne@FreeBSD.org> | 2024-06-14 18:02:05 +0000 |
| commit | 134f7b5fa91fa41e3c3c7caeaf1dff72018684e5 (patch) | |
| tree | 4d6aef70883ec30de8a46b1bbe612343389afbbf | |
| parent | 3ff981587ff8f05c06092d05edcc50f1ede1bbd6 (diff) | |
riscv: improve commentary around initial stvec
Make it explicit why we must set the trap vector before enabling virtual
memory.
Reviewed by: br, jhb, markj
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D45474
| -rw-r--r-- | sys/riscv/riscv/locore.S | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/sys/riscv/riscv/locore.S b/sys/riscv/riscv/locore.S index 5a7e15ba443b..7e885ab8ca89 100644 --- a/sys/riscv/riscv/locore.S +++ b/sys/riscv/riscv/locore.S @@ -197,7 +197,11 @@ pagetables: /* Page tables END */ - /* Setup supervisor trap vector */ + /* + * Set the supervisor trap vector temporarily. Enabling virtual memory + * may generate a page fault. We simply wish to continue onwards, so + * have the trap deliver us to 'va'. + */ 2: lla t0, va sub t0, t0, s9 @@ -221,7 +225,7 @@ va: lla gp, __global_pointer$ .option pop - /* Setup supervisor trap vector */ + /* Set the trap vector to the real handler. */ la t0, cpu_exception_handler csrw stvec, t0 @@ -342,7 +346,11 @@ ENTRY(mpentry) /* Get the kernel's load address */ jal get_physmem - /* Setup supervisor trap vector */ + /* + * Set the supervisor trap vector temporarily. Enabling virtual memory + * may generate a page fault. We simply wish to continue onwards, so + * have the trap deliver us to 'mpva'. + */ lla t0, mpva sub t0, t0, s9 li t1, KERNBASE @@ -365,7 +373,7 @@ mpva: lla gp, __global_pointer$ .option pop - /* Setup supervisor trap vector */ + /* Set the trap vector to the real handler. */ la t0, cpu_exception_handler csrw stvec, t0 |