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Subject[PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section
Date
As Eric said,
"what we need to do is move the variable vmcoreinfo_note out
of the kernel's .bss section. And modify the code to regenerate
and keep this information in something like the control page.

Definitely something like this needs a page all to itself, and ideally
far away from any other kernel data structures. I clearly was not
watching closely the data someone decided to keep this silly thing
in the kernel's .bss section."

This patch allocates extra pages for these vmcoreinfo_XXX variables,
one advantage is that it enhances some safety of vmcoreinfo, because
vmcoreinfo now is kept far away from other kernel data structures.

Suggested-by: Eric Biederman <ebiederm@xmission.com>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: Juergen Gross <jgross@suse.com>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
v3->v4:
-Rebased on the latest linux-next
-Handle S390 vmcoreinfo_note properly
-Handle the newly-added xen/mmu_pv.c

arch/ia64/kernel/machine_kexec.c | 5 -----
arch/s390/kernel/machine_kexec.c | 1 +
arch/s390/kernel/setup.c | 6 ------
arch/x86/kernel/crash.c | 2 +-
arch/x86/xen/mmu_pv.c | 4 ++--
include/linux/crash_core.h | 2 +-
kernel/crash_core.c | 27 +++++++++++++++++++++++----
kernel/ksysfs.c | 2 +-
8 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/arch/ia64/kernel/machine_kexec.c b/arch/ia64/kernel/machine_kexec.c
index 599507b..c14815d 100644
--- a/arch/ia64/kernel/machine_kexec.c
+++ b/arch/ia64/kernel/machine_kexec.c
@@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void)
#endif
}

-phys_addr_t paddr_vmcoreinfo_note(void)
-{
- return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note);
-}
-
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index 49a6bd4..3d0b14a 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void)
VMCOREINFO_SYMBOL(lowcore_ptr);
VMCOREINFO_SYMBOL(high_memory);
VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
+ mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
}

void machine_shutdown(void)
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 3ae756c..3d1d808 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -496,11 +496,6 @@ static void __init setup_memory_end(void)
pr_notice("The maximum memory size is %luMB\n", memory_end >> 20);
}

-static void __init setup_vmcoreinfo(void)
-{
- mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
-}
-
#ifdef CONFIG_CRASH_DUMP

/*
@@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p)
#endif

setup_resources();
- setup_vmcoreinfo();
setup_lowcore();
smp_fill_possible_mask();
cpu_detect_mhz_feature();
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 22217ec..44404e2 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
bufp += sizeof(Elf64_Phdr);
phdr->p_type = PT_NOTE;
phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
- phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
+ phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
(ehdr->e_phnum)++;

#ifdef CONFIG_X86_64
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 9d9ae66..35543fa 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -2723,8 +2723,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
phys_addr_t paddr_vmcoreinfo_note(void)
{
if (xen_pv_domain())
- return virt_to_machine(&vmcoreinfo_note).maddr;
+ return virt_to_machine(vmcoreinfo_note).maddr;
else
- return __pa_symbol(&vmcoreinfo_note);
+ return __pa(vmcoreinfo_note);
}
#endif /* CONFIG_KEXEC_CORE */
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index eb71a70..ba283a2 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -53,7 +53,7 @@
#define VMCOREINFO_PHYS_BASE(value) \
vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)

-extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
+extern u32 *vmcoreinfo_note;
extern size_t vmcoreinfo_size;
extern size_t vmcoreinfo_max_size;

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index fcbd568..0321f04 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -14,10 +14,10 @@
#include <asm/sections.h>

/* vmcoreinfo stuff */
-static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
-u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
+static unsigned char *vmcoreinfo_data;
size_t vmcoreinfo_size;
-size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
+size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
+u32 *vmcoreinfo_note;

/*
* parsing the "crashkernel" commandline
@@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void)

void crash_save_vmcoreinfo(void)
{
+ if (!vmcoreinfo_note)
+ return;
+
vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
update_vmcoreinfo_note();
}
@@ -356,11 +359,27 @@ void __weak arch_crash_save_vmcoreinfo(void)

phys_addr_t __weak paddr_vmcoreinfo_note(void)
{
- return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
+ return __pa(vmcoreinfo_note);
}

static int __init crash_save_vmcoreinfo_init(void)
{
+ /* One page should be enough for VMCOREINFO_BYTES under all archs */
+ vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
+ if (!vmcoreinfo_data) {
+ pr_warn("Memory allocation for vmcoreinfo_data failed\n");
+ return -ENOMEM;
+ }
+
+ vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
+ GFP_KERNEL | __GFP_ZERO);
+ if (!vmcoreinfo_note) {
+ free_page((unsigned long)vmcoreinfo_data);
+ vmcoreinfo_data = NULL;
+ pr_warn("Memory allocation for vmcoreinfo_note failed\n");
+ return -ENOMEM;
+ }
+
VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
VMCOREINFO_PAGESIZE(PAGE_SIZE);

diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 23cd706..c40a4e5 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
{
phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
return sprintf(buf, "%pa %x\n", &vmcore_base,
- (unsigned int)sizeof(vmcoreinfo_note));
+ (unsigned int)VMCOREINFO_NOTE_SIZE);
}
KERNEL_ATTR_RO(vmcoreinfo);

--
1.8.3.1
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