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Message-ID: <20130621161703.751b5f23@holzheu>
Date: Fri, 21 Jun 2013 16:17:03 +0200
From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
Jan Willeke <willeke@...ibm.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [PATCH v5 1/5] vmcore: Introduce ELF header in new memory
feature
On Fri, 14 Jun 2013 14:54:02 -0400
Vivek Goyal <vgoyal@...hat.com> wrote:
> On Fri, Jun 07, 2013 at 06:55:57PM +0200, Michael Holzheu wrote:
>
> [..]
> > @@ -935,10 +967,17 @@ static int __init vmcore_init(void)
> > {
> > int rc = 0;
> >
> > - /* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
> > - if (!(is_vmcore_usable()))
> > - return rc;
> > + /*
> > + * If elfcorehdr= has not been passed in cmdline, try to get the
> > + * header from 2nd kernel, then capture the dump.
> > + */
> > + if (!(is_vmcore_usable())) {
> > + rc = elfcorehdr_alloc();
> > + if (rc)
> > + return rc;
> > + }
>
> Hi Michael,
>
> Patch description says that elfcorehdr_alloc() returns the addr and
> size of elf headers. But that does not seem to be the case here. Has
> it been modified in later patches.
Sorry, that is a relict of one of my previous experiments where I tried
to implement elfcorehdr_addr() similar to the way as you suggest it now.
Because elfcorehdr_addr is a global variable, I decided to not pass
it in the functions. But of course I can change that again if you prefer
that.
> Also will it be better if we call elfcorehdr_alloc() always and then
> check for is_vmcore_usable().
>
> Something like.
>
> elfcorehdr_addr = elfcorehdr_alloc()
> if (elfcorehdr_addr < )
> return elfcorehdr_addr
>
> if (!(is_vmcore_usable()))
> return error
Ok, but then I think elfcorehdr_alloc() should also return
the elfcorehdr_size.
So what about the following patch:
---
fs/proc/vmcore.c | 65 +++++++++++++++++++++++++++++++++++++--------
include/linux/crash_dump.h | 6 ++++
2 files changed, 60 insertions(+), 11 deletions(-)
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -123,6 +123,36 @@ static ssize_t read_from_oldmem(char *bu
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_siz
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
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_siz
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
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_head
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_head
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_head
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_head
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_header
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();
@@ -943,7 +982,11 @@ static int __init vmcore_init(void)
pr_warn("Kdump: vmcore not initialized\n");
return rc;
}
-
+ elfcorehdr_free(elfcorehdr_addr);
+ /*
+ * elfcorehdr_addr must not be set to NULL here to keep
+ * is_kdump_kernel() working.
+ */
proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations);
if (proc_vmcore)
proc_vmcore->size = vmcore_size;
--- 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);
--
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