The patch titled
Subject: crash_core: fix and simplify the logic of crash_exclude_mem_range()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
crash_core-fix-and-simplify-the-logic-of-crash_exclude_mem_range.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/crash_core-fix-and-simplify-the-logic-of-crash_exclude_mem_range.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yuntao Wang <ytcoode@xxxxxxxxx>
Subject: crash_core: fix and simplify the logic of crash_exclude_mem_range()
Date: Tue, 2 Jan 2024 22:49:05 +0800
The purpose of crash_exclude_mem_range() is to remove all memory ranges
that overlap with [mstart-mend]. However, the current logic only removes
the first overlapping memory range.
Commit a2e9a95d2190 ("kexec: Improve & fix crash_exclude_mem_range() to
handle overlapping ranges") attempted to address this issue, but it did
not fix all error cases.
Let's fix and simplify the logic of crash_exclude_mem_range().
Link: https://lkml.kernel.org/r/20240102144905.110047-4-ytcoode@xxxxxxxxx
Signed-off-by: Yuntao Wang <ytcoode@xxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Cc: Takashi Iwai <tiwai@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/crash_core.c | 80 +++++++++++++++---------------------------
1 file changed, 29 insertions(+), 51 deletions(-)
--- a/kernel/crash_core.c~crash_core-fix-and-simplify-the-logic-of-crash_exclude_mem_range
+++ a/kernel/crash_core.c
@@ -566,9 +566,8 @@ int crash_prepare_elf64_headers(struct c
int crash_exclude_mem_range(struct crash_mem *mem,
unsigned long long mstart, unsigned long long mend)
{
- int i, j;
+ int i;
unsigned long long start, end, p_start, p_end;
- struct range temp_range = {0, 0};
for (i = 0; i < mem->nr_ranges; i++) {
start = mem->ranges[i].start;
@@ -576,72 +575,51 @@ int crash_exclude_mem_range(struct crash
p_start = mstart;
p_end = mend;
- if (mstart > end || mend < start)
+ if (p_start > end)
continue;
+ /*
+ * Because the memory ranges in mem->ranges are stored in
+ * ascending order, when we detect `p_end < start`, we can
+ * immediately exit the for loop, as the subsequent memory
+ * ranges will definitely be outside the range we are looking
+ * for.
+ */
+ if (p_end < start)
+ break;
+
/* Truncate any area outside of range */
- if (mstart < start)
+ if (p_start < start)
p_start = start;
- if (mend > end)
+ if (p_end > end)
p_end = end;
/* Found completely overlapping range */
if (p_start == start && p_end == end) {
- mem->ranges[i].start = 0;
- mem->ranges[i].end = 0;
- if (i < mem->nr_ranges - 1) {
- /* Shift rest of the ranges to left */
- for (j = i; j < mem->nr_ranges - 1; j++) {
- mem->ranges[j].start =
- mem->ranges[j+1].start;
- mem->ranges[j].end =
- mem->ranges[j+1].end;
- }
-
- /*
- * Continue to check if there are another overlapping ranges
- * from the current position because of shifting the above
- * mem ranges.
- */
- i--;
- mem->nr_ranges--;
- continue;
- }
+ memmove(&mem->ranges[i], &mem->ranges[i + 1],
+ (mem->nr_ranges - (i + 1)) * sizeof(mem->ranges[i]));
+ i--;
mem->nr_ranges--;
- return 0;
- }
-
- if (p_start > start && p_end < end) {
+ } else if (p_start > start && p_end < end) {
/* Split original range */
+ if (mem->nr_ranges >= mem->max_nr_ranges)
+ return -ENOMEM;
+
+ memmove(&mem->ranges[i + 2], &mem->ranges[i + 1],
+ (mem->nr_ranges - (i + 1)) * sizeof(mem->ranges[i]));
+
mem->ranges[i].end = p_start - 1;
- temp_range.start = p_end + 1;
- temp_range.end = end;
+ mem->ranges[i + 1].start = p_end + 1;
+ mem->ranges[i + 1].end = end;
+
+ i++;
+ mem->nr_ranges++;
} else if (p_start != start)
mem->ranges[i].end = p_start - 1;
else
mem->ranges[i].start = p_end + 1;
- break;
- }
-
- /* If a split happened, add the split to array */
- if (!temp_range.end)
- return 0;
-
- /* Split happened */
- if (i == mem->max_nr_ranges - 1)
- return -ENOMEM;
-
- /* Location where new range should go */
- j = i + 1;
- if (j < mem->nr_ranges) {
- /* Move over all ranges one slot towards the end */
- for (i = mem->nr_ranges - 1; i >= j; i--)
- mem->ranges[i + 1] = mem->ranges[i];
}
- mem->ranges[j].start = temp_range.start;
- mem->ranges[j].end = temp_range.end;
- mem->nr_ranges++;
return 0;
}
_
Patches currently in -mm which might be from ytcoode@xxxxxxxxx are
x86-crash-remove-the-unused-image-parameter-from-prepare_elf_headers.patch
x86-crash-use-sz_1m-macro-instead-of-hardcoded-value.patch
crash_core-fix-and-simplify-the-logic-of-crash_exclude_mem_range.patch
x86-crash-fix-potential-cmem-ranges-array-overflow.patch
crash_core-optimize-crash_exclude_mem_range.patch
