From 5830785322060ddd97b6baf7d8711a13738f61b5 Mon Sep 17 00:00:00 2001
From: Petr Tesarik <petr@tesarici.cz>
Date: Sat, 18 Nov 2023 22:09:50 +0100
Subject: [PATCH] elfdump: Fix page bitmaps for overlapping segments

When enumerating LOAD segments, do not update the current PFN position
if a previous segment ended on a higher address.

Signed-off-by: Petr Tesarik <petr@tesarici.cz>
---
 src/kdumpfile/elfdump.c | 12 ++++----
 tests/Makefile.am       |  1 +
 tests/elf-overlap       | 66 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+), 5 deletions(-)
 create mode 100755 tests/elf-overlap

diff --git a/src/kdumpfile/elfdump.c b/src/kdumpfile/elfdump.c
index e4dee2ff..bd5b791e 100644
--- a/src/kdumpfile/elfdump.c
+++ b/src/kdumpfile/elfdump.c
@@ -462,9 +462,10 @@ elf_get_bits(struct kdump_shared *shared,
 			set_bits(bits, cur - first, last - first);
 			return;
 		}
-		set_bits(bits, cur - first, next - first);
-
-		cur = next + 1;
+		if (cur <= next) {
+			set_bits(bits, cur - first, next - first);
+			cur = next + 1;
+		}
 		++pls;
 	} while (pls < &edp->load_sorted[edp->num_load_sorted]);
 
@@ -560,8 +561,9 @@ elf_find_clear(kdump_errmsg_t *err, struct kdump_shared *shared,
 	while (pls < &edp->load_sorted[edp->num_load_sorted] &&
 	       *idx >= addr_to_pfn(shared, pls->phys)) {
 		kdump_paddr_t size = ismem ? pls->memsz : pls->filesz;
-		*idx = addr_to_pfn(shared, pls->phys + size - 1);
-		++(*idx);
+		kdump_paddr_t pfn = addr_to_pfn(shared, pls->phys + size - 1);
+		if (pfn >= *idx)
+			*idx = pfn + 1;
 		++pls;
 	}
 }
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2f5f3c61..0c03b20b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -232,6 +232,7 @@ test_scripts = \
 	elf-partial \
 	elf-fractional \
 	elf-multiread \
+	elf-overlap \
 	elf-virt-phys-clash \
 	elf-vmcoreinfo \
 	elf-dom0-no-phys_base \
diff --git a/tests/elf-overlap b/tests/elf-overlap
new file mode 100755
index 00000000..af5b9f2b
--- /dev/null
+++ b/tests/elf-overlap
@@ -0,0 +1,66 @@
+#! /bin/sh
+
+#
+# Create an ELF file with overlapping LOAD segments and verify that
+# the page map is merged correctly
+#
+
+mkdir -p out || exit 99
+
+name=$( basename "$0" )
+datafile="out/${name}.data"
+dumpfile="out/${name}.dump"
+
+cat >"$datafile" <<EOF
+# first LOAD  |####|
+# second LOAD   |####|
+@phdr type=LOAD offset=0x1000 vaddr=0x1000 paddr=0x1000 memsz=0x4000
+55*0x1000
+@phdr type=LOAD vaddr=0x3000 paddr=0x3000 memsz=0x4000
+
+# first LOAD  |########|
+# second LOAD   |####|
+@phdr type=LOAD vaddr=0xa000 paddr=0xa000 memsz=0x8000
+55*0x2000
+@phdr type=LOAD vaddr=0xc000 paddr=0xc000 memsz=0x4000
+aa*0x2000
+
+# first LOAD  |####|
+# second LOAD      |##|
+@phdr type=LOAD vaddr=0x18000 paddr=0x18000 memsz=0x4000
+@phdr type=LOAD vaddr=0x1c000 paddr=0x1c000 memsz=0x2000
+aa*0x1000
+EOF
+
+./mkelf "$dumpfile" <<EOF
+ei_class = 2
+ei_data = 1
+e_machine = 62
+e_phoff = 64
+
+DATA = $datafile
+EOF
+rc=$?
+if [ $rc -ne 0 ]; then
+    echo "Cannot create ELF file" >&2
+    exit $rc
+fi
+echo "Created ELF dump: $dumpfile"
+
+./checkattr "$dumpfile" <<EOF
+file = directory:
+file.set.number = number:1
+file.set.0 = directory:
+file.set.0.fd = number
+file.format = string: elf
+
+file.pagemap = bitmap:0x02 0x3c 0x00 0x10
+memory.pagemap = bitmap:0x7e 0xfc 0x03 0x3f
+EOF
+rc=$?
+if [ $rc -ne 0 ]; then
+    echo "Attribute check failed" >&2
+    exit $rc
+fi
+
+exit 0