From 15eb77f873255cf9f4d703b63cfbd23c46579654 Mon Sep 17 00:00:00 2001

From: Hari Bathini <hbathini@linux.ibm.com>

Date: Wed, 6 Apr 2022 15:08:37 +0530

Subject: [PATCH] powerpc/fadump: fix PT_LOAD segment for boot memory area

References: bsc#1103269 ltc#169948 git-fixes

Patch-mainline: v5.19-rc1

Git-commit: 15eb77f873255cf9f4d703b63cfbd23c46579654

Boot memory area is setup as separate PT_LOAD segment in the vmcore

as it is moved by f/w, on crash, to a destination address provided by

the kernel. Having separate PT_LOAD segment helps in handling the

different physical address and offset for boot memory area in the

vmcore.

Commit ced1bf52f477 ("powerpc/fadump: merge adjacent memory ranges to

reduce PT_LOAD segements") inadvertly broke this pre-condition for

cases where some of the first kernel memory is available adjacent to

boot memory area. This scenario is rare but possible when memory for

fadump could not be reserved adjacent to boot memory area owing to

memory hole or such. Reading memory from a vmcore exported in such

scenario provides incorrect data.  Fix it by ensuring no other region

is folded into boot memory area.

Fixes: ced1bf52f477 ("powerpc/fadump: merge adjacent memory ranges to reduce PT_LOAD segements")

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Link: https://lore.kernel.org/r/20220406093839.206608-2-hbathini@linux.ibm.com

[ms: we don't have boot_mem_top, use boot_memory_size instead]

Acked-by: Michal Suchanek <msuchanek@suse.de>

---

 arch/powerpc/kernel/fadump.c | 8 ++++++--

 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c

--- a/arch/powerpc/kernel/fadump.c

+++ b/arch/powerpc/kernel/fadump.c

@@ -867,7 +867,6 @@ static int fadump_alloc_mem_ranges(struct fadump_mrange_info *mrange_info)

 				       sizeof(struct fadump_memory_range));

 	return 0;

 }

-

 static inline int fadump_add_mem_range(struct fadump_mrange_info *mrange_info,

 				       u64 base, u64 end)

 {

@@ -886,7 +885,12 @@ static inline int fadump_add_mem_range(struct fadump_mrange_info *mrange_info,

 		start = mem_ranges[mrange_info->mem_range_cnt - 1].base;

 		size  = mem_ranges[mrange_info->mem_range_cnt - 1].size;

-		if ((start + size) == base)

+		/*

+		 * Boot memory area needs separate PT_LOAD segment(s) as it

+		 * is moved to a different location at the time of crash.

+		 * So, fold only if the region is not boot memory area.

+		 */

+		if ((start + size) == base && start >= fw_dump.boot_memory_size)

 			is_adjacent = true;

 	}

 	if (!is_adjacent) {

-- 

2.35.3