linux-kernel - [PATCH] MIPS: reserve the memblock right after the kernel

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Date:   Fri,  6 Nov 2020 15:10:01 +0100
From:   Alexander A Sverdlin <alexander.sverdlin@...ia.com>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-mips@...r.kernel.org
Cc:     Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Paul Burton <paulburton@...nel.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] MIPS: reserve the memblock right after the kernel

From: Alexander Sverdlin <alexander.sverdlin@...ia.com>

Linux doesn't own the memory immediately after the kernel image. On Octeon
bootloader places a shared structure right close after the kernel _end,
refer to "struct cvmx_bootinfo *octeon_bootinfo" in cavium-octeon/setup.c.

If check_kernel_sections_mem() rounds the PFNs up, first memblock_alloc()
inside early_init_dt_alloc_memory_arch() <= device_tree_init() returns
memory block overlapping with the above octeon_bootinfo structure, which
is being overwritten afterwards.

Cc: stable@...r.kernel.org
Fixes: a94e4f24ec83 ("MIPS: init: Drop boot_mem_map")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...ia.com>
---
 arch/mips/kernel/setup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 0d42532..f6cf2f6 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -504,6 +504,12 @@ static void __init check_kernel_sections_mem(void)
 	if (!memblock_is_region_memory(start, size)) {
 		pr_info("Kernel sections are not in the memory maps\n");
 		memblock_add(start, size);
+		/*
+		 * Octeon bootloader places shared data structure right after
+		 * the kernel => make sure it will not be corrupted.
+		 */
+		memblock_reserve(__pa_symbol(&_end),
+				 start + size - __pa_symbol(&_end));
 	}
 }
 
-- 
2.10.2