Hi Drew,
On 4/20/21 7:59 PM, Andrew Jones wrote:
> Rather than making too many assumptions about the memory layout
> in mmu code, just set up the page tables per the memory regions
> (which means putting all the memory layout assumptions in setup).
> To ensure we get the right default flags set we need to split the
> primary region into two regions for code and data.
>
> We still only expect the primary regions to be present, but the
> next patch will remove that assumption too.
>
> (Unfortunately we still have an assumption in setup_mmu. We assume
> the range 3G-4G is available for the virtual memory allocator. We'll
> need to remove that assumption as well with another patch in order
> to support arbitrary memory maps.)
>
> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> lib/arm/asm/setup.h | 1 +
> lib/arm/mmu.c | 26 +++++++++++++++-----------
> lib/arm/setup.c | 29 +++++++++++++++++++++--------
> 3 files changed, 37 insertions(+), 19 deletions(-)
>
> diff --git a/lib/arm/asm/setup.h b/lib/arm/asm/setup.h
> index c8afb2493f8d..210c14f818fb 100644
> --- a/lib/arm/asm/setup.h
> +++ b/lib/arm/asm/setup.h
> @@ -15,6 +15,7 @@ extern int nr_cpus;
>
> #define MR_F_PRIMARY (1U << 0)
> #define MR_F_IO (1U << 1)
> +#define MR_F_CODE (1U << 2)
> #define MR_F_UNKNOWN (1U << 31)
>
> struct mem_region {
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index ee0c79142ba1..4e3cf37e33d0 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -20,8 +20,6 @@
>
> #include <linux/compiler.h>
>
> -extern unsigned long etext;
> -
> pgd_t *mmu_idmap;
>
> /* CPU 0 starts with disabled MMU */
> @@ -157,7 +155,7 @@ void mmu_set_range_sect(pgd_t *pgtable, uintptr_t virt_offset,
>
> void *setup_mmu(phys_addr_t phys_end)
> {
> - uintptr_t code_end = (uintptr_t)&etext;
> + struct mem_region *r;
>
> /* 3G-4G region is reserved for vmalloc, cap phys_end at 3G */
> if (phys_end > (3ul << 30))
> @@ -173,14 +171,20 @@ void *setup_mmu(phys_addr_t phys_end)
> if (!mmu_idmap)
> mmu_idmap = alloc_page();
>
> - /* armv8 requires code shared between EL1 and EL0 to be read-only */
> - mmu_set_range_ptes(mmu_idmap, PHYS_OFFSET,
> - PHYS_OFFSET, code_end,
> - __pgprot(PTE_WBWA | PTE_RDONLY | PTE_USER));
> -
> - mmu_set_range_ptes(mmu_idmap, code_end,
> - code_end, phys_end,
> - __pgprot(PTE_WBWA | PTE_USER));
> + for (r = mem_regions; r->end; ++r) {
> + if (r->flags & MR_F_IO) {
> + continue;
> + } else if (r->flags & MR_F_CODE) {
> + assert_msg(r->flags & MR_F_PRIMARY, "Unexpected code region");
> + /* armv8 requires code shared between EL1 and EL0 to be read-only */
> + mmu_set_range_ptes(mmu_idmap, r->start, r->start, r->end,
> + __pgprot(PTE_WBWA | PTE_USER | PTE_RDONLY));
> + } else {
> + assert_msg(r->flags & MR_F_PRIMARY, "Unexpected data region");
> + mmu_set_range_ptes(mmu_idmap, r->start, r->start, r->end,
> + __pgprot(PTE_WBWA | PTE_USER));
> + }
> + }
>
> mmu_enable(mmu_idmap);
> return mmu_idmap;
> diff --git a/lib/arm/setup.c b/lib/arm/setup.c
> index 9c16f6004e9f..7db308b70744 100644
> --- a/lib/arm/setup.c
> +++ b/lib/arm/setup.c
> @@ -31,6 +31,7 @@
> #define NR_INITIAL_MEM_REGIONS 16
>
> extern unsigned long stacktop;
> +extern unsigned long etext;
>
> struct timer_state __timer_state;
>
> @@ -88,10 +89,12 @@ unsigned int mem_region_get_flags(phys_addr_t paddr)
>
> static void mem_init(phys_addr_t freemem_start)
> {
> + phys_addr_t code_end = (phys_addr_t)(unsigned long)&etext;
> struct dt_pbus_reg regs[NR_INITIAL_MEM_REGIONS];
> - struct mem_region primary, mem = {
> + struct mem_region mem = {
> .start = (phys_addr_t)-1,
> };
> + struct mem_region *primary = NULL;
> phys_addr_t base, top;
> int nr_regs, nr_io = 0, i;
>
> @@ -110,8 +113,6 @@ static void mem_init(phys_addr_t freemem_start)
> nr_regs = dt_get_memory_params(regs, NR_INITIAL_MEM_REGIONS - nr_io);
> assert(nr_regs > 0);
>
> - primary = (struct mem_region){ 0 };
> -
> for (i = 0; i < nr_regs; ++i) {
> struct mem_region *r = &mem_regions[nr_io + i];
>
> @@ -123,7 +124,7 @@ static void mem_init(phys_addr_t freemem_start)
> */
> if (freemem_start >= r->start && freemem_start < r->end) {
> r->flags |= MR_F_PRIMARY;
> - primary = *r;
> + primary = r;
> }
>
> /*
> @@ -135,13 +136,25 @@ static void mem_init(phys_addr_t freemem_start)
> if (r->end > mem.end)
> mem.end = r->end;
> }
> - assert(primary.end != 0);
> + assert(primary);
> assert(!(mem.start & ~PHYS_MASK) && !((mem.end - 1) & ~PHYS_MASK));
>
> - __phys_offset = primary.start; /* PHYS_OFFSET */
> - __phys_end = primary.end; /* PHYS_END */
> + __phys_offset = primary->start; /* PHYS_OFFSET */
> + __phys_end = primary->end; /* PHYS_END */
> +
> + /* Split the primary region into two regions; code and data */
> + mem_regions[nr_io + i] = (struct mem_region){
Nitpick: you could change that to nr_io + nr_regs, to make it obsolutely obvious
that the new region is appended to the array. This works because the static array
is created with NR_INITIAL_MEM_REGIONS + 1 (but it does mean that we loose the
empty region at the end if nr_io + nr_regs = NR_INITIAL_MEM_REGIONS).
> + .start = code_end,
> + .end = primary->end,
> + .flags = MR_F_PRIMARY,
> + };
> + *primary = (struct mem_region){
> + .start = primary->start,
> + .end = code_end,
> + .flags = MR_F_PRIMARY | MR_F_CODE,
> + };
>
> - phys_alloc_init(freemem_start, primary.end - freemem_start);
> + phys_alloc_init(freemem_start, __phys_end - freemem_start);
> phys_alloc_set_minimum_alignment(SMP_CACHE_BYTES);
>
> phys_alloc_get_unused(&base, &top);
The nitpick is a matter of preference, and the patch looks really good now, it was
a lot easier to figure out what is going on:
Reviewed-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Thanks,
Alex
