From 21dd515b0e99da85770cabf1deeaec83ca628418 Mon Sep 17 00:00:00 2001
From: James Morse <james.morse@arm.com>
Date: Mon, 23 Jul 2018 10:57:28 +0900
Subject: [PATCH 08/20] arm64: export memblock_reserve()d regions via
 /proc/iomem

Git-commit: 50d7ba36b916d0fd4687149ec143bf49c326523f
Patch-mainline: v4.19-rc1
References: bsc#1106892

There has been some confusion around what is necessary to prevent kexec
overwriting important memory regions. memblock: reserve, or nomap?
Only memblock nomap regions are reported via /proc/iomem, kexec's
user-space doesn't know about memblock_reserve()d regions.

Until commit f56ab9a5b73ca ("efi/arm: Don't mark ACPI reclaim memory
as MEMBLOCK_NOMAP") the ACPI tables were nomap, now they are reserved
and thus possible for kexec to overwrite with the new kernel or initrd.
But this was always broken, as the UEFI memory map is also reserved
and not marked as nomap.

Exporting both nomap and reserved memblock types is a nuisance as
they live in different memblock structures which we can't walk at
the same time.

Take a second walk over memblock.reserved and add new 'reserved'
subnodes for the memblock_reserved() regions that aren't already
described by the existing code. (e.g. Kernel Code)

We use reserve_region_with_split() to find the gaps in existing named
regions. This handles the gap between 'kernel code' and 'kernel data'
which is memblock_reserve()d, but already partially described by
request_standard_resources(). e.g.:
| 80000000-dfffffff : System RAM
|   80080000-80ffffff : Kernel code
|   81000000-8158ffff : reserved
|   81590000-8237efff : Kernel data
|   a0000000-dfffffff : Crash kernel
| e00f0000-f949ffff : System RAM

reserve_region_with_split needs kzalloc() which isn't available when
request_standard_resources() is called, use an initcall.

Reported-by: Bhupesh Sharma <bhsharma@redhat.com>
Reported-by: Tyler Baicar <tbaicar@codeaurora.org>
Suggested-by: Akashi Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: James Morse <james.morse@arm.com>
Fixes: d28f6df1305a ("arm64/kexec: Add core kexec support")
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
CC: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 arch/arm64/kernel/setup.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 91fd8cafcf3f..0ce6d29600ea 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -238,6 +238,44 @@ static void __init request_standard_resources(void)
 	}
 }
 
+static int __init reserve_memblock_reserved_regions(void)
+{
+	phys_addr_t start, end, roundup_end = 0;
+	struct resource *mem, *res;
+	u64 i;
+
+	for_each_reserved_mem_region(i, &start, &end) {
+		if (end <= roundup_end)
+			continue; /* done already */
+
+		start = __pfn_to_phys(PFN_DOWN(start));
+		end = __pfn_to_phys(PFN_UP(end)) - 1;
+		roundup_end = end;
+
+		res = kzalloc(sizeof(*res), GFP_ATOMIC);
+		if (WARN_ON(!res))
+			return -ENOMEM;
+		res->start = start;
+		res->end = end;
+		res->name  = "reserved";
+		res->flags = IORESOURCE_MEM;
+
+		mem = request_resource_conflict(&iomem_resource, res);
+		/*
+		 * We expected memblock_reserve() regions to conflict with
+		 * memory created by request_standard_resources().
+		 */
+		if (WARN_ON_ONCE(!mem))
+			continue;
+		kfree(res);
+
+		reserve_region_with_split(mem, start, end, "reserved");
+	}
+
+	return 0;
+}
+arch_initcall(reserve_memblock_reserved_regions);
+
 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
 
 void __init setup_arch(char **cmdline_p)
-- 
2.11.0