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riscv: Properly export reserved regions in /proc/iomem

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The /proc/iomem represents the kernel's memory map. Regions marked
with "Reserved" tells the user that the range should not be tampered
with. Kexec-tools, when using the older kexec_load syscall relies on
the "Reserved" regions to build the memory segments, that will be the
target of the new kexec'd kernel.

The RISC-V port tries to expose all reserved regions to userland, but
some regions were not properly exposed: Regions that resided in both
the "regular" and reserved memory block, e.g. the EFI Memory Map. A
missing entry could result in reserved memory being overwritten.

It turns out, that arm64, and loongarch had a similar issue a while
back:

  commit d91680e687f4 ("arm64: Fix /proc/iomem for reserved but not memory regions")
  commit 50d7ba36b916 ("arm64: export memblock_reserve()d regions via /proc/iomem")

Similar to the other ports, resolve the issue by splitting the regions
in an arch initcall, since we need a working allocator.

Fixes: ffe0e5261268 ("RISC-V: Improve init_resources()")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250409182129.634415-1-bjorn@kernel.org
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
This commit is contained in:
Björn Töpel 2025-04-09 20:21:27 +02:00 committed by Alexandre Ghiti
parent 4410160560
commit e94eb7ea6f
1 changed files with 35 additions and 1 deletions
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36
arch/riscv/kernel/setup.c
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@ -66,6 +66,9 @@ static struct resource bss_res = { .name = "Kernel bss", };
static struct resource elfcorehdr_res = { .name = "ELF Core hdr", };
#endif
static int num_standard_resources;
static struct resource *standard_resources;
static int __init add_resource(struct resource *parent,
struct resource *res)
{
@ -139,7 +142,7 @@ static void __init init_resources(void)
struct resource *res = NULL;
struct resource *mem_res = NULL;
size_t mem_res_sz = 0;
int num_resources = 0, res_idx = 0;
int num_resources = 0, res_idx = 0, non_resv_res = 0;
int ret = 0;
/* + 1 as memblock_alloc() might increase memblock.reserved.cnt */
@ -193,6 +196,7 @@ static void __init init_resources(void)
/* Add /memory regions to the resource tree */
for_each_mem_region(region) {
res = &mem_res[res_idx--];
non_resv_res++;
if (unlikely(memblock_is_nomap(region))) {
res->name = "Reserved";
@ -210,6 +214,9 @@ static void __init init_resources(void)
goto error;
}
num_standard_resources = non_resv_res;
standard_resources = &mem_res[res_idx + 1];
/* Clean-up any unused pre-allocated resources */
if (res_idx >= 0)
memblock_free(mem_res, (res_idx + 1) * sizeof(*mem_res));
@ -221,6 +228,33 @@ static void __init init_resources(void)
memblock_free(mem_res, mem_res_sz);
}
static int __init reserve_memblock_reserved_regions(void)
{
u64 i, j;
for (i = 0; i < num_standard_resources; i++) {
struct resource *mem = &standard_resources[i];
phys_addr_t r_start, r_end, mem_size = resource_size(mem);
if (!memblock_is_region_reserved(mem->start, mem_size))
continue;
for_each_reserved_mem_range(j, &r_start, &r_end) {
resource_size_t start, end;
start = max(PFN_PHYS(PFN_DOWN(r_start)), mem->start);
end = min(PFN_PHYS(PFN_UP(r_end)) - 1, mem->end);
if (start > mem->end || end < mem->start)
continue;
reserve_region_with_split(mem, start, end, "Reserved");
}
}
return 0;
}
arch_initcall(reserve_memblock_reserved_regions);
static void __init parse_dtb(void)
{