Re: [PATCH] RISC-V: Fix FIXMAP area corruption on RV32 systems
From: Christoph Hellwig
Date: Sun Aug 18 2019 - 14:19:22 EST
> +#define FIXADDR_TOP (VMALLOC_START)
Nit: no need for the braces, the definitions below don't use it
> +#ifdef CONFIG_64BIT
> +#define FIXADDR_SIZE PMD_SIZE
> +#define FIXADDR_SIZE PGDIR_SIZE
> +#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
> - * Task size is 0x4000000000 for RV64 or 0xb800000 for RV32.
> + * Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32.
> * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
> #ifdef CONFIG_64BIT
> #define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
> -#define TASK_SIZE VMALLOC_START
> +#define TASK_SIZE FIXADDR_START
Mentioning the addresses is a little weird. IMHO this would be
a much nicer place to explain the high-level memory layout, including
maybe a little ASCII art. Also we could have one #ifdef CONFIG_64BIT
for both related values. Last but not least instead of saying that
something should be dividable it would be nice to have a BUILD_BUG_ON
to enforce it.
Either way we are late in the cycle, so I guess this is ok for now:
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
But I'd love to see this area improved a little further as it is full
of mine fields.