> > /* Traverse through the Elf headers and find the region where
> > * _stext symbol is located in. That's where kernel is mapped */
> > - stext_sym = get_kernel_stext_sym();
> > + stext_sym = get_kernel_sym("stext");
>
>
> I think this should be get_kernel_sym("_stext");
>
> Apart from that as Simon already mentioned, due to commit
> 9f62cbd ("kexec/arch/i386: Add support for KASLR memory randomization")
> this patch does not apply cleanly.
Pratyush, I had a cleanup patch below, but I did not get time to test it
so it is not ready to send out.
The basic thought is to move the page_offset_base code to
get_kernel_page_offset(), there is also another issue is for old kernel
or kernel without kaslr built-in there will be an unnecessary error
message but I have not get any idea how to fix it.
Would you like to take below cleanup patch along with your next version?
It is also fine to leave it as a future improvement to me.
Thanks
Dave
---
kexec/arch/i386/crashdump-x86.c | 158 ++++++++++++++++++++--------------------
1 file changed, 82 insertions(+), 76 deletions(-)
--- kexec-tools.orig/kexec/arch/i386/crashdump-x86.c
+++ kexec-tools/kexec/arch/i386/crashdump-x86.c
@@ -54,10 +54,59 @@
extern struct arch_options_t arch_options;
+/* Retrieve kernel symbol virtual address from /proc/kallsyms */
+static unsigned long long get_kernel_sym(const char *symbol)
+{
+ const char *kallsyms = "/proc/kallsyms";
+ char sym[128];
+ char line[128];
+ FILE *fp;
+ unsigned long long vaddr;
+ char type;
+
+ fp = fopen(kallsyms, "r");
+ if (!fp) {
+ fprintf(stderr, "Cannot open %s\n", kallsyms);
+ return 0;
+ }
+
+ while(fgets(line, sizeof(line), fp) != NULL) {
+ if (sscanf(line, "%Lx %c %s", &vaddr, &type, sym) != 3)
+ continue;
+ if (strcmp(sym, symbol) == 0) {
+ dbgprintf("kernel symbol %s vaddr = %16llx\n", symbol,
vaddr);
+ return vaddr;
+ }
+ }
+
+ fprintf(stderr, "Cannot get kernel %s symbol address\n", symbol);
+
+ return 0;
+}
+
static int get_kernel_page_offset(struct kexec_info *UNUSED(info),
- struct crash_elf_info *elf_info)
+ struct crash_elf_info *elf_info,
+ struct mem_ehdr *ehdr)
{
int kv;
+ struct mem_phdr *phdr, *end_phdr;
+ const unsigned long long pud_mask = ~((1 << 30) - 1);
+ unsigned long long vaddr, lowest_vaddr = 0;
+
+ end_phdr = &ehdr->e_phdr[ehdr->e_phnum];
+ /* Search for the real PAGE_OFFSET when KASLR memory randomization
+ * is enabled */
+ if (get_kernel_sym("page_offset_base") != 0) {
+ for(phdr = ehdr->e_phdr; phdr != end_phdr; phdr++) {
+ if (phdr->p_type == PT_LOAD) {
+ vaddr = phdr->p_vaddr & pud_mask;
+ if (lowest_vaddr == 0 || lowest_vaddr > vaddr)
+ lowest_vaddr = vaddr;
+ }
+ }
+ if (lowest_vaddr != 0)
+ elf_info->page_offset = lowest_vaddr;
+ }
if (elf_info->machine == EM_X86_64) {
kv = kernel_version();
@@ -102,35 +151,6 @@ static int get_kernel_paddr(struct kexec
return -1;
}
-/* Retrieve kernel symbol virtual address from /proc/kallsyms */
-static unsigned long long get_kernel_sym(const char *symbol)
-{
- const char *kallsyms = "/proc/kallsyms";
- char sym[128];
- char line[128];
- FILE *fp;
- unsigned long long vaddr;
- char type;
-
- fp = fopen(kallsyms, "r");
- if (!fp) {
- fprintf(stderr, "Cannot open %s\n", kallsyms);
- return 0;
- }
-
- while(fgets(line, sizeof(line), fp) != NULL) {
- if (sscanf(line, "%Lx %c %s", &vaddr, &type, sym) != 3)
- continue;
- if (strcmp(sym, symbol) == 0) {
- dbgprintf("kernel symbol %s vaddr = %16llx\n", symbol,
vaddr);
- return vaddr;
- }
- }
-
- fprintf(stderr, "Cannot get kernel %s symbol address\n", symbol);
- return 0;
-}
-
/* Retrieve info regarding virtual address kernel has been compiled for and
* size of the kernel from /proc/kcore. Current /proc/kcore parsing from
* from kexec-tools fails because of malformed elf notes. A kernel patch has
@@ -139,19 +159,12 @@ static unsigned long long get_kernel_sym
* we should get rid of backward compatible code. */
static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
- struct crash_elf_info *elf_info)
+ struct crash_elf_info *elf_info,
+ struct mem_ehdr *ehdr)
{
- int result;
- const char kcore[] = "/proc/kcore";
- char *buf;
- struct mem_ehdr ehdr;
struct mem_phdr *phdr, *end_phdr;
int align;
- off_t size;
- uint32_t elf_flags = 0;
uint64_t stext_sym;
- const unsigned long long pud_mask = ~((1 << 30) - 1);
- unsigned long long vaddr, lowest_vaddr = 0;
if (elf_info->machine != EM_X86_64)
return 0;
@@ -160,45 +173,13 @@ static int get_kernel_vaddr_and_size(str
return 0;
align = getpagesize();
- buf = slurp_file_len(kcore, KCORE_ELF_HEADERS_SIZE, &size);
- if (!buf) {
- fprintf(stderr, "Cannot read %s: %s\n", kcore, strerror(errno));
- return -1;
- }
- /* Don't perform checks to make sure stated phdrs and shdrs are
- * actually present in the core file. It is not practical
- * to read the GB size file into a user space buffer, Given the
- * fact that we don't use any info from that.
- */
- elf_flags |= ELF_SKIP_FILESZ_CHECK;
- result = build_elf_core_info(buf, size, &ehdr, elf_flags);
- if (result < 0) {
- /* Perhaps KCORE_ELF_HEADERS_SIZE is too small? */
- fprintf(stderr, "ELF core (kcore) parse failed\n");
- return -1;
- }
-
- end_phdr = &ehdr.e_phdr[ehdr.e_phnum];
-
- /* Search for the real PAGE_OFFSET when KASLR memory randomization
- * is enabled */
- if (get_kernel_sym("page_offset_base") != 0) {
- for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) {
- if (phdr->p_type == PT_LOAD) {
- vaddr = phdr->p_vaddr & pud_mask;
- if (lowest_vaddr == 0 || lowest_vaddr > vaddr)
- lowest_vaddr = vaddr;
- }
- }
- if (lowest_vaddr != 0)
- elf_info->page_offset = lowest_vaddr;
- }
+ end_phdr = &ehdr->e_phdr[ehdr->e_phnum];
/* Traverse through the Elf headers and find the region where
* _stext symbol is located in. That's where kernel is mapped */
stext_sym = get_kernel_sym("_stext");
- for(phdr = ehdr.e_phdr; stext_sym && phdr != end_phdr; phdr++) {
+ for(phdr = ehdr->e_phdr; stext_sym && phdr != end_phdr; phdr++) {
if (phdr->p_type == PT_LOAD) {
unsigned long long saddr = phdr->p_vaddr;
unsigned long long eaddr = phdr->p_vaddr +
phdr->p_memsz;
@@ -223,7 +204,7 @@ static int get_kernel_vaddr_and_size(str
* /proc/kallsyms, Traverse through the Elf headers again and
* find the region where kernel is mapped using hard-coded
* kernel mapping boundries */
- for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) {
+ for(phdr = ehdr->e_phdr; phdr != end_phdr; phdr++) {
if (phdr->p_type == PT_LOAD) {
unsigned long long saddr = phdr->p_vaddr;
unsigned long long eaddr = phdr->p_vaddr +
phdr->p_memsz;
@@ -887,6 +868,12 @@ int load_crashdump_segments(struct kexec
struct memory_range *mem_range, *memmap_p;
struct crash_elf_info elf_info;
unsigned kexec_arch;
+ char *buf;
+ off_t size;
+ struct mem_ehdr ehdr;
+ uint32_t elf_flags = 0;
+ const char kcore[] = "/proc/kcore";
+ int result;
memset(&elf_info, 0x0, sizeof(elf_info));
@@ -943,13 +930,32 @@ int load_crashdump_segments(struct kexec
elf_info.class = ELFCLASS64;
}
- if (get_kernel_page_offset(info, &elf_info))
+ buf = slurp_file_len(kcore, KCORE_ELF_HEADERS_SIZE, &size);
+ if (!buf) {
+ fprintf(stderr, "Cannot read %s: %s\n", kcore, strerror(errno));
+ return -1;
+ }
+
+ /* Don't perform checks to make sure stated phdrs and shdrs are
+ * actually present in the core file. It is not practical
+ * to read the GB size file into a user space buffer, Given the
+ * fact that we don't use any info from that.
+ */
+ elf_flags |= ELF_SKIP_FILESZ_CHECK;
+ result = build_elf_core_info(buf, size, &ehdr, elf_flags);
+ if (result < 0) {
+ /* Perhaps KCORE_ELF_HEADERS_SIZE is too small? */
+ fprintf(stderr, "ELF core (kcore) parse failed\n");
+ return -1;
+ }
+
+ if (get_kernel_page_offset(info, &elf_info, &ehdr))
return -1;
if (get_kernel_paddr(info, &elf_info))
return -1;
- if (get_kernel_vaddr_and_size(info, &elf_info))
+ if (get_kernel_vaddr_and_size(info, &elf_info, &ehdr))
return -1;
/* Memory regions which panic kernel can safely use to boot into */
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