Messages in this thread Patch in this message | | | From | Petr Tesarik <> | Subject | Overlapping reserved regions at boot | Date | Tue, 29 Nov 2011 15:01:51 +0100 |
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Hello,
while working on the upcoming SLES11 SP2, I ran into an issue with booting the panic kernel on a kernel crash. In the first iteration I found out that the initial register backing store gets overwritten with zeroes, causing a kernel crash shortly afterwards.
Further investigation revealed that rsvd_region[] contains overlapping entries: find_memmap_space() returns a pointer which lies between KERNEL_START and _end. This is correct with the EFI memmap as patched by the kexec purgatory code. That code removes vmlinux LOAD segments from the usable map, but there is a pretty large hole between the gate section and the per-cpu section.
With the following patch, the panic kernel can boot and save the crash dump.
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
--- a/arch/ia64/kernel/setup.c +++ b/arch/ia64/kernel/setup.c @@ -225,6 +225,23 @@ } } +/* merge overlaps */ +static int __init +merge_regions (struct rsvd_region *rsvd_region, int max) +{ + int i; + for (i = 1; i < max; ++i) { + if (rsvd_region[i].start >= rsvd_region[i-1].end) + continue; + if (rsvd_region[i].end > rsvd_region[i-1].end) + rsvd_region[i-1].end = rsvd_region[i].end; + --max; + memmove(&rsvd_region[i], &rsvd_region[i+1], + (max - i) * sizeof(struct rsvd_region)); + } + return max; +} + /* * Request address space for all standard resources */ @@ -275,6 +292,7 @@ if (ret == 0 && size > 0) { if (!base) { sort_regions(rsvd_region, *n); + *n = merge_regions(rsvd_region, *n); base = kdump_find_rsvd_region(size, rsvd_region, *n); } @@ -392,6 +410,7 @@ BUG_ON(IA64_MAX_RSVD_REGIONS + 1 < n); sort_regions(rsvd_region, num_rsvd_regions); + num_rsvd_regions = merge_regions(rsvd_region, num_rsvd_regions); }
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