linux-kernel - [RFC v2 18/43] kexec: PKRAM: avoid clobbering already preserved pages

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Date:   Tue, 30 Mar 2021 14:35:53 -0700
From:   Anthony Yznaga <anthony.yznaga@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     willy@...radead.org, corbet@....net, tglx@...utronix.de,
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        linux-doc@...r.kernel.org, kexec@...ts.infradead.org
Subject: [RFC v2 18/43] kexec: PKRAM: avoid clobbering already preserved pages

Ensure destination ranges of the kexec segments do not overlap
with any kernel pages marked to be preserved across kexec.

For kexec_load, return EADDRNOTAVAIL if overlap is detected.

For kexec_file_load, skip ranges containing preserved pages when
seaching for available ranges to use.

Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
 kernel/kexec_core.c | 3 +++
 kernel/kexec_file.c | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index a0b6780740c8..fda4abb865ff 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -37,6 +37,7 @@
 #include <linux/compiler.h>
 #include <linux/hugetlb.h>
 #include <linux/objtool.h>
+#include <linux/pkram.h>
 
 #include <asm/page.h>
 #include <asm/sections.h>
@@ -175,6 +176,8 @@ int sanity_check_segment_list(struct kimage *image)
 			return -EADDRNOTAVAIL;
 		if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
 			return -EADDRNOTAVAIL;
+		if (pkram_has_preserved_pages(mstart, mend))
+			return -EADDRNOTAVAIL;
 	}
 
 	/* Verify our destination addresses do not overlap.
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 1ec47a3c60dd..94109bcdbeff 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -516,6 +516,11 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
 			continue;
 		}
 
+		if (pkram_has_preserved_pages(temp_start, temp_end + 1)) {
+			temp_start = temp_start - PAGE_SIZE;
+			continue;
+		}
+
 		/* We found a suitable memory range */
 		break;
 	} while (1);
-- 
1.8.3.1