Re: [PATCH v6 1/5] vmcore: Introduce ELF header in new memory feature
From: Vivek Goyal
Date: Tue Jul 02 2013 - 11:28:34 EST
On Mon, Jul 01, 2013 at 09:32:35PM +0200, Michael Holzheu wrote:
>
Currently for s390 we create the ELF core header in the 2nd kernel
>
with a small trick. We relocate the addresses in the ELF header in
>
a way that for the /proc/vmcore code it seems to be in the 1st kernel
>
(old) memory and the read_from_oldmem() returns the correct data.
>
This allows the /proc/vmcore code to use the ELF header in the
>
2nd kernel.
>
>
This patch now exchanges the old mechanism with the new and much
>
cleaner function call override feature that now offcially allows to
>
create the ELF core header in the 2nd kernel.
>
>
To use the new feature the following function have to be defined
>
by the architecture backend code to read from new memory:
>
>
* elfcorehdr_alloc: Allocate ELF header
>
* elfcorehdr_free: Free the memory of the ELF header
>
* elfcorehdr_read: Read from ELF header
>
* elfcorehdr_read_notes: Read from ELF notes
>
>
Signed-off-by: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
Looks good to me.
Acked-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Vivek
>
---
>
fs/proc/vmcore.c | 61 ++++++++++++++++++++++++++++++++++++++--------
>
include/linux/crash_dump.h | 6 +++++
>
2 files changed, 57 insertions(+), 10 deletions(-)
>
>
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
>
index 0f6db52..c28189c 100644
>
--- a/fs/proc/vmcore.c
>
+++ b/fs/proc/vmcore.c
>
@@ -123,6 +123,36 @@ static ssize_t read_from_oldmem(char *buf, size_t count,
>
return read;
>
}
>
>
+/*
>
+ * Architectures may override this function to allocate ELF header in 2nd kernel
>
+ */
>
+int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
>
+{
>
+ return 0;
>
+}
>
+
>
+/*
>
+ * Architectures may override this function to free header
>
+ */
>
+void __weak elfcorehdr_free(unsigned long long addr)
>
+{}
>
+
>
+/*
>
+ * Architectures may override this function to read from ELF header
>
+ */
>
+ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>
+{
>
+ return read_from_oldmem(buf, count, ppos, 0);
>
+}
>
+
>
+/*
>
+ * Architectures may override this function to read from notes sections
>
+ */
>
+ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
>
+{
>
+ return read_from_oldmem(buf, count, ppos, 0);
>
+}
>
+
>
/* Read from the ELF header and then the crash dump. On error, negative value is
>
* returned otherwise number of bytes read are returned.
>
*/
>
@@ -322,7 +352,7 @@ static int __init update_note_header_size_elf64(const Elf64_Ehdr *ehdr_ptr)
>
notes_section = kmalloc(max_sz, GFP_KERNEL);
>
if (!notes_section)
>
return -ENOMEM;
>
- rc = read_from_oldmem(notes_section, max_sz, &offset, 0);
>
+ rc = elfcorehdr_read_notes(notes_section, max_sz, &offset);
>
if (rc < 0) {
>
kfree(notes_section);
>
return rc;
>
@@ -409,7 +439,8 @@ static int __init copy_notes_elf64(const Elf64_Ehdr *ehdr_ptr, char *notes_buf)
>
if (phdr_ptr->p_type != PT_NOTE)
>
continue;
>
offset = phdr_ptr->p_offset;
>
- rc = read_from_oldmem(notes_buf, phdr_ptr->p_memsz, &offset, 0);
>
+ rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz,
>
+ &offset);
>
if (rc < 0)
>
return rc;
>
notes_buf += phdr_ptr->p_memsz;
>
@@ -510,7 +541,7 @@ static int __init update_note_header_size_elf32(const Elf32_Ehdr *ehdr_ptr)
>
notes_section = kmalloc(max_sz, GFP_KERNEL);
>
if (!notes_section)
>
return -ENOMEM;
>
- rc = read_from_oldmem(notes_section, max_sz, &offset, 0);
>
+ rc = elfcorehdr_read_notes(notes_section, max_sz, &offset);
>
if (rc < 0) {
>
kfree(notes_section);
>
return rc;
>
@@ -597,7 +628,8 @@ static int __init copy_notes_elf32(const Elf32_Ehdr *ehdr_ptr, char *notes_buf)
>
if (phdr_ptr->p_type != PT_NOTE)
>
continue;
>
offset = phdr_ptr->p_offset;
>
- rc = read_from_oldmem(notes_buf, phdr_ptr->p_memsz, &offset, 0);
>
+ rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz,
>
+ &offset);
>
if (rc < 0)
>
return rc;
>
notes_buf += phdr_ptr->p_memsz;
>
@@ -793,7 +825,7 @@ static int __init parse_crash_elf64_headers(void)
>
addr = elfcorehdr_addr;
>
>
/* Read Elf header */
>
- rc = read_from_oldmem((char*)&ehdr, sizeof(Elf64_Ehdr), &addr, 0);
>
+ rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf64_Ehdr), &addr);
>
if (rc < 0)
>
return rc;
>
>
@@ -820,7 +852,7 @@ static int __init parse_crash_elf64_headers(void)
>
if (!elfcorebuf)
>
return -ENOMEM;
>
addr = elfcorehdr_addr;
>
- rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0);
>
+ rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr);
>
if (rc < 0)
>
goto fail;
>
>
@@ -849,7 +881,7 @@ static int __init parse_crash_elf32_headers(void)
>
addr = elfcorehdr_addr;
>
>
/* Read Elf header */
>
- rc = read_from_oldmem((char*)&ehdr, sizeof(Elf32_Ehdr), &addr, 0);
>
+ rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf32_Ehdr), &addr);
>
if (rc < 0)
>
return rc;
>
>
@@ -875,7 +907,7 @@ static int __init parse_crash_elf32_headers(void)
>
if (!elfcorebuf)
>
return -ENOMEM;
>
addr = elfcorehdr_addr;
>
- rc = read_from_oldmem(elfcorebuf, elfcorebuf_sz_orig, &addr, 0);
>
+ rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr);
>
if (rc < 0)
>
goto fail;
>
>
@@ -902,7 +934,7 @@ static int __init parse_crash_elf_headers(void)
>
int rc=0;
>
>
addr = elfcorehdr_addr;
>
- rc = read_from_oldmem(e_ident, EI_NIDENT, &addr, 0);
>
+ rc = elfcorehdr_read(e_ident, EI_NIDENT, &addr);
>
if (rc < 0)
>
return rc;
>
if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
>
@@ -935,7 +967,14 @@ static int __init vmcore_init(void)
>
{
>
int rc = 0;
>
>
- /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
>
+ /* Allow architectures to allocate ELF header in 2nd kernel */
>
+ rc = elfcorehdr_alloc(&elfcorehdr_addr, &elfcorehdr_size);
>
+ if (rc)
>
+ return rc;
>
+ /*
>
+ * If elfcorehdr= has been passed in cmdline or created in 2nd kernel,
>
+ * then capture the dump.
>
+ */
>
if (!(is_vmcore_usable()))
>
return rc;
>
rc = parse_crash_elf_headers();
>
@@ -943,6 +982,8 @@ static int __init vmcore_init(void)
>
pr_warn("Kdump: vmcore not initialized\n");
>
return rc;
>
}
>
+ elfcorehdr_free(elfcorehdr_addr);
>
+ elfcorehdr_addr = ELFCORE_ADDR_ERR;
>
>
proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations);
>
if (proc_vmcore)
>
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
>
index 37e4f8d..6571f82 100644
>
--- a/include/linux/crash_dump.h
>
+++ b/include/linux/crash_dump.h
>
@@ -12,6 +12,12 @@
>
extern unsigned long long elfcorehdr_addr;
>
extern unsigned long long elfcorehdr_size;
>
>
+extern int __weak elfcorehdr_alloc(unsigned long long *addr,
>
+ unsigned long long *size);
>
+extern void __weak elfcorehdr_free(unsigned long long addr);
>
+extern ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos);
>
+extern ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos);
>
+
>
extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
>
unsigned long, int);
>
>
--
>
1.8.2.2
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