lkml.org 
[lkml]   [2017]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 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>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
arch/ia64/kernel/machine_kexec.c | 5 -----
arch/x86/kernel/crash.c | 2 +-
include/linux/kexec.h | 2 +-
kernel/kexec_core.c | 29 ++++++++++++++++++++++++-----
kernel/ksysfs.c | 2 +-
5 files changed, 27 insertions(+), 13 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/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 3741461..4d35fbb 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -456,7 +456,7 @@ 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/include/linux/kexec.h b/include/linux/kexec.h
index e98e546..f1c601b 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -317,7 +317,7 @@ extern void *kexec_purgatory_get_symbol_addr(struct kimage *image,
extern struct resource crashk_low_res;
typedef u32 note_buf_t[KEXEC_NOTE_BYTES/4];
extern note_buf_t __percpu *crash_notes;
-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/kexec_core.c b/kernel/kexec_core.c
index bfe62d5..e3a4bda 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -52,10 +52,10 @@
note_buf_t __percpu *crash_notes;

/* 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;

/* Flag to indicate we are going to kexec a new kernel */
bool kexec_in_progress = false;
@@ -1369,6 +1369,9 @@ 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();
}
@@ -1397,13 +1400,29 @@ void vmcoreinfo_append_str(const char *fmt, ...)
void __weak arch_crash_save_vmcoreinfo(void)
{}

-phys_addr_t __weak paddr_vmcoreinfo_note(void)
+phys_addr_t 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 ee1bc1b..9de6fcc 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -130,7 +130,7 @@ 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
\
 
 \ /
  Last update: 2017-03-20 06:49    [W:0.068 / U:1.548 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site