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Subject[tip: efi/urgent] efi/memreserve: Register reservations as 'reserved' in /proc/iomem
The following commit has been merged into the efi/urgent branch of tip:

Commit-ID: ab0eb16205b43ece4c78e2259e681ff3d645ea66
Gitweb: https://git.kernel.org/tip/ab0eb16205b43ece4c78e2259e681ff3d645ea66
Author: Ard Biesheuvel <ardb@kernel.org>
AuthorDate: Fri, 06 Dec 2019 16:55:37
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 08 Dec 2019 12:42:18 +01:00

efi/memreserve: Register reservations as 'reserved' in /proc/iomem

Memory regions that are reserved using efi_mem_reserve_persistent()
are recorded in a special EFI config table which survives kexec,
allowing the incoming kernel to honour them as well. However,
such reservations are not visible in /proc/iomem, and so the kexec
tools that load the incoming kernel and its initrd into memory may
overwrite these reserved regions before the incoming kernel has a
chance to reserve them from further use.

Address this problem by adding these reservations to /proc/iomem as
they are created. Note that reservations that are inherited from a
previous kernel are memblock_reserve()'d early on, so they are already
visible in /proc/iomem.

Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Cc: <stable@vger.kernel.org> # v5.4+
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191206165542.31469-2-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
drivers/firmware/efi/efi.c | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index d101f07..b096195 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -979,6 +979,24 @@ static int __init efi_memreserve_map_root(void)
return 0;
}

+static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)
+{
+ struct resource *res, *parent;
+
+ res = kzalloc(sizeof(struct resource), GFP_ATOMIC);
+ if (!res)
+ return -ENOMEM;
+
+ res->name = "reserved";
+ res->flags = IORESOURCE_MEM;
+ res->start = addr;
+ res->end = addr + size - 1;
+
+ /* we expect a conflict with a 'System RAM' region */
+ parent = request_resource_conflict(&iomem_resource, res);
+ return parent ? request_resource(parent, res) : 0;
+}
+
int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
{
struct linux_efi_memreserve *rsv;
@@ -1003,7 +1021,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
rsv->entry[index].size = size;

memunmap(rsv);
- return 0;
+ return efi_mem_reserve_iomem(addr, size);
}
memunmap(rsv);
}
@@ -1013,6 +1031,12 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
if (!rsv)
return -ENOMEM;

+ rc = efi_mem_reserve_iomem(__pa(rsv), SZ_4K);
+ if (rc) {
+ free_page((unsigned long)rsv);
+ return rc;
+ }
+
/*
* The memremap() call above assumes that a linux_efi_memreserve entry
* never crosses a page boundary, so let's ensure that this remains true
@@ -1029,7 +1053,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
efi_memreserve_root->next = __pa(rsv);
spin_unlock(&efi_mem_reserve_persistent_lock);

- return 0;
+ return efi_mem_reserve_iomem(addr, size);
}

static int __init efi_memreserve_root_init(void)
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