* [patch v3 1/2] kdump: Add infrastructure for unmapping crashkernel memory
2011-09-15 9:04 [patch v3 0/2] kdump: Allow removal of page tables for crashkernel memory Michael Holzheu
@ 2011-09-15 9:04 ` Michael Holzheu
2011-09-15 9:04 ` [patch v3 2/2] s390: Add architecture code " Michael Holzheu
1 sibling, 0 replies; 3+ messages in thread
From: Michael Holzheu @ 2011-09-15 9:04 UTC (permalink / raw)
To: vgoyal, akpm
Cc: ebiederm, mahesh, schwidefsky, heiko.carstens, kexec,
linux-kernel, linux-s390
[-- Attachment #1: s390-kdump-common-crash_map_pages.patch --]
[-- Type: text/plain, Size: 3427 bytes --]
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
This patch introduces a mechanism that allows architecture backends to
remove page tables for the crashkernel memory. This can protect the loaded
kdump kernel from being overwritten by broken kernel code. Two new
functions crash_map_reserved_pages() and crash_unmap_reserved_pages() are
added that can be implemented by architecture code. The
crash_map_reserved_pages() function is called before and
crash_unmap_reserved_pages() after the crashkernel segments are loaded. The
functions are also called in crash_shrink_memory() to create/remove page
tables when the crashkernel memory size is reduced.
To support architectures that have large pages this patch also introduces
a new define KEXEC_CRASH_MEM_ALIGN. The crashkernel start and size must
always be aligned with KEXEC_CRASH_MEM_ALIGN.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
---
include/linux/kexec.h | 6 ++++++
kernel/kexec.c | 21 +++++++++++++++++++--
2 files changed, 25 insertions(+), 2 deletions(-)
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -37,6 +37,10 @@
#define KEXEC_CRASH_CONTROL_MEMORY_LIMIT KEXEC_CONTROL_MEMORY_LIMIT
#endif
+#ifndef KEXEC_CRASH_MEM_ALIGN
+#define KEXEC_CRASH_MEM_ALIGN PAGE_SIZE
+#endif
+
#define KEXEC_NOTE_HEAD_BYTES ALIGN(sizeof(struct elf_note), 4)
#define KEXEC_CORE_NOTE_NAME "CORE"
#define KEXEC_CORE_NOTE_NAME_BYTES ALIGN(sizeof(KEXEC_CORE_NOTE_NAME), 4)
@@ -133,6 +137,8 @@ extern void crash_kexec(struct pt_regs *
int kexec_should_crash(struct task_struct *);
void crash_save_cpu(struct pt_regs *regs, int cpu);
void crash_save_vmcoreinfo(void);
+void crash_map_reserved_pages(void);
+void crash_unmap_reserved_pages(void);
void arch_crash_save_vmcoreinfo(void);
void vmcoreinfo_append_str(const char *fmt, ...)
__attribute__ ((format (printf, 1, 2)));
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -999,6 +999,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned lon
kimage_free(xchg(&kexec_crash_image, NULL));
result = kimage_crash_alloc(&image, entry,
nr_segments, segments);
+ crash_map_reserved_pages();
}
if (result)
goto out;
@@ -1015,6 +1016,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned lon
goto out;
}
kimage_terminate(image);
+ if (flags & KEXEC_ON_CRASH)
+ crash_unmap_reserved_pages();
}
/* Install the new kernel, and Uninstall the old */
image = xchg(dest_image, image);
@@ -1026,6 +1029,18 @@ out:
return result;
}
+/*
+ * Add and remove page tables for crashkernel memory
+ *
+ * Provide an empty default implementation here -- architecture
+ * code may override this
+ */
+void __weak crash_map_reserved_pages(void)
+{}
+
+void __weak crash_unmap_reserved_pages(void)
+{}
+
#ifdef CONFIG_COMPAT
asmlinkage long compat_sys_kexec_load(unsigned long entry,
unsigned long nr_segments,
@@ -1134,14 +1149,16 @@ int crash_shrink_memory(unsigned long ne
goto unlock;
}
- start = roundup(start, PAGE_SIZE);
- end = roundup(start + new_size, PAGE_SIZE);
+ start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
+ end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
+ crash_map_reserved_pages();
crash_free_reserved_phys_range(end, crashk_res.end);
if ((start == end) && (crashk_res.parent != NULL))
release_resource(&crashk_res);
crashk_res.end = end - 1;
+ crash_unmap_reserved_pages();
unlock:
mutex_unlock(&kexec_mutex);
^ permalink raw reply [flat|nested] 3+ messages in thread* [patch v3 2/2] s390: Add architecture code for unmapping crashkernel memory
2011-09-15 9:04 [patch v3 0/2] kdump: Allow removal of page tables for crashkernel memory Michael Holzheu
2011-09-15 9:04 ` [patch v3 1/2] kdump: Add infrastructure for unmapping " Michael Holzheu
@ 2011-09-15 9:04 ` Michael Holzheu
1 sibling, 0 replies; 3+ messages in thread
From: Michael Holzheu @ 2011-09-15 9:04 UTC (permalink / raw)
To: vgoyal, akpm
Cc: ebiederm, mahesh, schwidefsky, heiko.carstens, kexec,
linux-kernel, linux-s390
[-- Attachment #1: s390-kdump-arch-crash_map_pages.patch --]
[-- Type: text/plain, Size: 3419 bytes --]
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
This patch implements the crash_map_pages() function for s390.
KEXEC_CRASH_MEM_ALIGN is set to HPAGE_SIZE, in order to support
kernel mappings that use large pages. We also use HPAGE_SIZE alignment
for CONFIG_HUGETLB_PAGE=n in order to have the same 1 MiB alignment on
all s390 systems.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
---
arch/s390/include/asm/kexec.h | 3 +++
arch/s390/kernel/machine_kexec.c | 31 +++++++++++++++++++++++++++++++
arch/s390/kernel/setup.c | 10 ++++++----
3 files changed, 40 insertions(+), 4 deletions(-)
--- a/arch/s390/include/asm/kexec.h
+++ b/arch/s390/include/asm/kexec.h
@@ -36,6 +36,9 @@
/* Allocate one page for the pdp and the second for the code */
#define KEXEC_CONTROL_PAGE_SIZE 4096
+/* Alignment of crashkernel memory */
+#define KEXEC_CRASH_MEM_ALIGN HPAGE_SIZE
+
/* The native architecture */
#define KEXEC_ARCH KEXEC_ARCH_S390
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -243,6 +243,37 @@ static void __machine_kdump(void *image)
#endif
/*
+ * Map or unmap crashkernel memory
+ */
+static void crash_map_pages(int enable)
+{
+ unsigned long size = resource_size(&crashk_res);
+
+ BUG_ON(crashk_res.start % KEXEC_CRASH_MEM_ALIGN ||
+ size % KEXEC_CRASH_MEM_ALIGN);
+ if (enable)
+ vmem_add_mapping(crashk_res.start, size);
+ else
+ vmem_remove_mapping(crashk_res.start, size);
+}
+
+/*
+ * Map crashkernel memory
+ */
+void crash_map_reserved_pages(void)
+{
+ crash_map_pages(1);
+}
+
+/*
+ * Unmap crashkernel memory
+ */
+void crash_unmap_reserved_pages(void)
+{
+ crash_map_pages(0);
+}
+
+/*
* Give back memory to hypervisor before new kdump is loaded
*/
static int machine_kexec_prepare_kdump(void)
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -446,6 +446,7 @@ static void __init setup_resources(void)
res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
switch (memory_chunk[i].type) {
case CHUNK_READ_WRITE:
+ case CHUNK_CRASHK:
res->name = "System RAM";
break;
case CHUNK_READ_ONLY:
@@ -706,8 +707,8 @@ static void __init reserve_crashkernel(v
&crash_base);
if (rc || crash_size == 0)
return;
- crash_base = PAGE_ALIGN(crash_base);
- crash_size = PAGE_ALIGN(crash_size);
+ crash_base = ALIGN(crash_base, KEXEC_CRASH_MEM_ALIGN);
+ crash_size = ALIGN(crash_size, KEXEC_CRASH_MEM_ALIGN);
if (register_memory_notifier(&kdump_mem_nb))
return;
if (!crash_base)
@@ -727,7 +728,7 @@ static void __init reserve_crashkernel(v
crashk_res.start = crash_base;
crashk_res.end = crash_base + crash_size - 1;
insert_resource(&iomem_resource, &crashk_res);
- reserve_kdump_bootmem(crash_base, crash_size, CHUNK_READ_WRITE);
+ reserve_kdump_bootmem(crash_base, crash_size, CHUNK_CRASHK);
pr_info("Reserving %lluMB of memory at %lluMB "
"for crashkernel (System RAM: %luMB)\n",
crash_size >> 20, crash_base >> 20, memory_end >> 20);
@@ -802,7 +803,8 @@ setup_memory(void)
for (i = 0; i < MEMORY_CHUNKS && memory_chunk[i].size > 0; i++) {
unsigned long start_chunk, end_chunk, pfn;
- if (memory_chunk[i].type != CHUNK_READ_WRITE)
+ if (memory_chunk[i].type != CHUNK_READ_WRITE &&
+ memory_chunk[i].type != CHUNK_CRASHK)
continue;
start_chunk = PFN_DOWN(memory_chunk[i].addr);
end_chunk = start_chunk + PFN_DOWN(memory_chunk[i].size);
^ permalink raw reply [flat|nested] 3+ messages in thread