Re: [PATCH][5/6]ELF format dump file access

[Hariprasad Nellitheertha]

Regards, Hari
-- 
Hariprasad Nellitheertha
Linux Technology Center
India Software Labs
IBM India, Bangalore


This patch contains the code that provides an ELF format interface to the
previous kernel's memory post kexec reboot.

Signed off by Hariprasad Nellitheertha <hari@xxxxxxxxxx>


---

 linux-2.6.9-rc1-hari/fs/proc/Makefile           |    1 
 linux-2.6.9-rc1-hari/fs/proc/kcore.c            |   10 -
 linux-2.6.9-rc1-hari/fs/proc/proc_misc.c        |   12 +
 linux-2.6.9-rc1-hari/fs/proc/vmcore.c           |  238 ++++++++++++++++++++++++
 linux-2.6.9-rc1-hari/include/linux/crash_dump.h |    8 
 linux-2.6.9-rc1-hari/include/linux/proc_fs.h    |    2 
 6 files changed, 266 insertions(+), 5 deletions(-)

diff -puN fs/proc/Makefile~kd-elf-269rc1-mm5 fs/proc/Makefile
--- linux-2.6.9-rc1/fs/proc/Makefile~kd-elf-269rc1-mm5	2004-09-15 17:36:53.000000000 +0530
+++ linux-2.6.9-rc1-hari/fs/proc/Makefile	2004-09-15 17:36:53.000000000 +0530
@@ -11,4 +11,5 @@ proc-y       += inode.o root.o base.o ge
 		kmsg.o proc_tty.o proc_misc.o
 
 proc-$(CONFIG_PROC_KCORE)	+= kcore.o
+proc-$(CONFIG_CRASH_DUMP)	+= vmcore.o
 proc-$(CONFIG_PROC_DEVICETREE)	+= proc_devtree.o
diff -puN fs/proc/kcore.c~kd-elf-269rc1-mm5 fs/proc/kcore.c
--- linux-2.6.9-rc1/fs/proc/kcore.c~kd-elf-269rc1-mm5	2004-09-15 17:36:53.000000000 +0530
+++ linux-2.6.9-rc1-hari/fs/proc/kcore.c	2004-09-15 17:36:53.000000000 +0530
@@ -114,7 +114,7 @@ static size_t get_kcore_size(int *nphdr,
 /*
  * determine size of ELF note
  */
-static int notesize(struct memelfnote *en)
+int notesize(struct memelfnote *en)
 {
 	int sz;
 
@@ -129,7 +129,7 @@ static int notesize(struct memelfnote *e
 /*
  * store a note in the header buffer
  */
-static char *storenote(struct memelfnote *men, char *bufp)
+char *storenote(struct memelfnote *men, char *bufp)
 {
 	struct elf_note en;
 
@@ -156,7 +156,7 @@ static char *storenote(struct memelfnote
  * store an ELF coredump header in the supplied buffer
  * nphdr is the number of elf_phdr to insert
  */
-static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
+void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff, struct kcore_list *clist)
 {
 	struct elf_prstatus prstatus;	/* NT_PRSTATUS */
 	struct elf_prpsinfo prpsinfo;	/* NT_PRPSINFO */
@@ -208,7 +208,7 @@ static void elf_kcore_store_hdr(char *bu
 	nhdr->p_align	= 0;
 
 	/* setup ELF PT_LOAD program header for every area */
-	for (m=kclist; m; m=m->next) {
+	for (m=clist; m; m=m->next) {
 		phdr = (struct elf_phdr *) bufp;
 		bufp += sizeof(struct elf_phdr);
 		offset += sizeof(struct elf_phdr);
@@ -305,7 +305,7 @@ read_kcore(struct file *file, char __use
 			return -ENOMEM;
 		}
 		memset(elf_buf, 0, elf_buflen);
-		elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
+		elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen, kclist);
 		read_unlock(&kclist_lock);
 		if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
 			kfree(elf_buf);
diff -puN fs/proc/proc_misc.c~kd-elf-269rc1-mm5 fs/proc/proc_misc.c
--- linux-2.6.9-rc1/fs/proc/proc_misc.c~kd-elf-269rc1-mm5	2004-09-15 17:36:53.000000000 +0530
+++ linux-2.6.9-rc1-hari/fs/proc/proc_misc.c	2004-09-15 17:36:53.000000000 +0530
@@ -44,6 +44,7 @@
 #include <linux/jiffies.h>
 #include <linux/sysrq.h>
 #include <linux/vmalloc.h>
+#include <linux/bootmem.h>
 #include <linux/crash_dump.h>
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -584,6 +585,7 @@ static struct file_operations proc_crash
 #endif
 
 struct proc_dir_entry *proc_root_kcore;
+struct proc_dir_entry *proc_vmcore;
 
 static void create_seq_entry(char *name, mode_t mode, struct file_operations *f)
 {
@@ -678,6 +680,16 @@ void __init proc_misc_init(void)
 				(size_t)high_memory - PAGE_OFFSET + PAGE_SIZE;
 	}
 #endif
+#ifdef CONFIG_CRASH_DUMP
+	if (dump_enabled) {
+		proc_vmcore = create_proc_entry("vmcore", S_IRUSR, NULL);
+		if (proc_vmcore) {
+			proc_vmcore->proc_fops = &proc_vmcore_operations;
+			proc_vmcore->size =
+			(size_t)(saved_max_pfn << PAGE_SHIFT);
+		}
+	}
+#endif
 #ifdef CONFIG_MAGIC_SYSRQ
 	entry = create_proc_entry("sysrq-trigger", S_IWUSR, NULL);
 	if (entry)
diff -puN /dev/null fs/proc/vmcore.c
--- /dev/null	2003-01-30 15:54:37.000000000 +0530
+++ linux-2.6.9-rc1-hari/fs/proc/vmcore.c	2004-09-15 17:36:53.000000000 +0530
@@ -0,0 +1,238 @@
+/*
+ *	fs/proc/vmcore.c Interface for accessing the crash
+ * 				 dump from the system's previous life.
+ * 	Heavily borrowed from fs/proc/kcore.c
+ *	Created by: Hariprasad Nellitheertha (hari@xxxxxxxxxx)
+ *	Copyright (C) IBM Corporation, 2004. All rights reserved
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/proc_fs.h>
+#include <linux/user.h>
+#include <linux/a.out.h>
+#include <linux/elf.h>
+#include <linux/elfcore.h>
+#include <linux/vmalloc.h>
+#include <linux/proc_fs.h>
+#include <linux/highmem.h>
+#include <linux/bootmem.h>
+#include <linux/init.h>
+#include <linux/crash_dump.h>
+#include <asm/uaccess.h>
+#include <asm/io.h>
+
+/* This is to re-use the kcore header creation code */
+static struct kcore_list vmcore_mem;
+
+static int open_vmcore(struct inode * inode, struct file * filp)
+{
+	return 0;
+}
+
+static ssize_t read_vmcore(struct file *,char __user *,size_t, loff_t *);
+
+struct file_operations proc_vmcore_operations = {
+	.read		= read_vmcore,
+	.open		= open_vmcore,
+};
+
+#define BACKUP_START CRASH_BACKUP_BASE
+#define BACKUP_END CRASH_BACKUP_BASE + CRASH_BACKUP_SIZE
+#define REG_SIZE sizeof(elf_gregset_t)
+
+struct memelfnote
+{
+	const char *name;
+	int type;
+	unsigned int datasz;
+	void *data;
+};
+
+static size_t get_vmcore_size(int *nphdr, size_t *elf_buflen)
+{
+	size_t size;
+
+	/* We need 1 PT_LOAD segment headers
+	 * In addition, we need one PT_NOTE header
+	 */
+	*nphdr = 2;
+	size = (size_t)(saved_max_pfn << PAGE_SHIFT);
+
+	*elf_buflen =	sizeof(struct elfhdr) +
+			(*nphdr + 2)*sizeof(struct elf_phdr) +
+			3 * sizeof(struct memelfnote) +
+			sizeof(struct elf_prstatus) +
+			sizeof(struct elf_prpsinfo) +
+			sizeof(struct task_struct);
+	*elf_buflen = PAGE_ALIGN(*elf_buflen);
+	return size + *elf_buflen;
+}
+
+/*
+ * Reads from the oldmem device from given offset till
+ * given count
+ */
+static ssize_t read_from_oldmem(char *buf, size_t count,
+			     loff_t *ppos, int userbuf)
+{
+	unsigned long pfn, p = *ppos;
+	size_t read = 0;
+
+	pfn = p / PAGE_SIZE;
+	p = p % PAGE_SIZE;
+
+	if (pfn > saved_max_pfn) {
+		read = -EINVAL;
+		goto done;
+	}
+
+	if (count > PAGE_SIZE - p)
+		count = PAGE_SIZE - p;
+
+	if (copy_oldmem_page(pfn, buf, count, userbuf)) {
+		read = -EFAULT;
+		goto done;
+	}
+
+	*ppos += count;
+done:
+	return read;
+}
+
+/*
+ * store an ELF crash dump header in the supplied buffer
+ * nphdr is the number of elf_phdr to insert
+ */
+static void elf_vmcore_store_hdr(char *bufp, int nphdr, int dataoff)
+{
+	struct elf_prstatus prstatus;	/* NT_PRSTATUS */
+	struct memelfnote notes[1];
+	char reg_buf[REG_SIZE];
+	loff_t reg_ppos;
+	char *buf = bufp;
+
+	vmcore_mem.addr = (unsigned long)__va(0);
+	vmcore_mem.size = saved_max_pfn << PAGE_SHIFT;
+	vmcore_mem.next = NULL;
+
+	/* Re-use the kcore code */
+	elf_kcore_store_hdr(bufp, nphdr, dataoff, &vmcore_mem);
+	buf += sizeof(struct elfhdr) + 2*sizeof(struct elf_phdr);
+
+	/* set up the process status */
+	notes[0].name = "CORE";
+	notes[0].type = NT_PRSTATUS;
+	notes[0].datasz = sizeof(struct elf_prstatus);
+	notes[0].data = &prstatus;
+
+	memset(&prstatus, 0, sizeof(struct elf_prstatus));
+
+	/* 1 - Get the registers from the reserved memory area */
+	reg_ppos = BACKUP_END + CRASH_RELOCATE_SIZE;
+	read_from_oldmem(reg_buf, REG_SIZE, &reg_ppos, 0);
+	elf_core_copy_regs(&prstatus.pr_reg, (struct pt_regs *)reg_buf);
+	buf = storenote(&notes[0], buf);
+}
+
+/*
+ * read from the ELF header and then the crash dump
+ */
+static ssize_t read_vmcore(
+struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
+{
+	ssize_t acc = 0;
+	size_t size, tsz;
+	size_t elf_buflen;
+	int nphdr;
+	unsigned long start;
+
+	tsz =  get_vmcore_size(&nphdr, &elf_buflen);
+	proc_vmcore->size = size = tsz + elf_buflen;
+	if (buflen == 0 || *fpos >= size) {
+		goto done;
+	}
+
+	/* trim buflen to not go beyond EOF */
+	if (buflen > size - *fpos)
+		buflen = size - *fpos;
+
+	/* construct an ELF core header if we'll need some of it */
+	if (*fpos < elf_buflen) {
+		char * elf_buf;
+
+		tsz = elf_buflen - *fpos;
+		if (buflen < tsz)
+			tsz = buflen;
+		elf_buf = kmalloc(elf_buflen, GFP_ATOMIC);
+		if (!elf_buf) {
+			acc = -ENOMEM;
+			goto done;
+		}
+		memset(elf_buf, 0, elf_buflen);
+		elf_vmcore_store_hdr(elf_buf, nphdr, elf_buflen);
+		if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
+			kfree(elf_buf);
+			acc = -EFAULT;
+			goto done;
+		}
+		kfree(elf_buf);
+		buflen -= tsz;
+		*fpos += tsz;
+		buffer += tsz;
+		acc += tsz;
+
+		/* leave now if filled buffer already */
+		if (buflen == 0) {
+			goto done;
+		}
+	}
+
+	start = *fpos - elf_buflen;
+	if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
+		tsz = buflen;
+
+	while (buflen) {
+		unsigned long p;
+
+		if ((start < 0) || (start >= size))
+			if (clear_user(buffer, tsz)) {
+				acc = -EFAULT;
+				goto done;
+			}
+
+		/* tsz contains actual len of dump to be read.
+		 * buflen is the total len that was requested.
+		 * This may contain part of ELF header. start
+		 * is the fpos for the oldmem region
+		 * If the file position corresponds to the second
+		 * kernel's memory, we just return zeroes
+		 */
+		p = start;
+		if ((p >= BACKUP_START) && (p < BACKUP_END)) {
+			if (clear_user(buffer, tsz)) {
+				acc = -EFAULT;
+				goto done;
+			}
+
+			goto read_done;
+		} else if (p < CRASH_RELOCATE_SIZE)
+			p += BACKUP_END;
+
+		if (read_from_oldmem(buffer, tsz, (loff_t *)&p, 1)) {
+			acc = -EINVAL;
+			goto done;
+		}
+
+read_done:
+		buflen -= tsz;
+		*fpos += tsz;
+		buffer += tsz;
+		acc += tsz;
+		start += tsz;
+		tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
+	}
+
+done:
+	return acc;
+}
diff -puN include/linux/crash_dump.h~kd-elf-269rc1-mm5 include/linux/crash_dump.h
--- linux-2.6.9-rc1/include/linux/crash_dump.h~kd-elf-269rc1-mm5	2004-09-15 17:36:53.000000000 +0530
+++ linux-2.6.9-rc1-hari/include/linux/crash_dump.h	2004-09-15 17:36:53.000000000 +0530
@@ -1,8 +1,16 @@
 #include <linux/kexec.h>
 #include <linux/smp_lock.h>
 #include <linux/device.h>
+#include <linux/proc_fs.h>
 #include <asm/crash_dump.h>
 
+extern unsigned long saved_max_pfn;
+extern struct memelfnote memelfnote;
+extern int notesize(struct memelfnote *);
+extern char *storenote(struct memelfnote *, char *);
+extern ssize_t copy_oldmem_page(unsigned long, char *, size_t, int);
+extern void elf_kcore_store_hdr(char *, int, int, struct kcore_list *);
+
 #ifdef CONFIG_CRASH_DUMP
 extern int crash_dump_on;
 static inline void crash_machine_kexec(void)
diff -puN include/linux/proc_fs.h~kd-elf-269rc1-mm5 include/linux/proc_fs.h
--- linux-2.6.9-rc1/include/linux/proc_fs.h~kd-elf-269rc1-mm5	2004-09-15 17:36:53.000000000 +0530
+++ linux-2.6.9-rc1-hari/include/linux/proc_fs.h	2004-09-15 17:36:53.000000000 +0530
@@ -82,6 +82,7 @@ extern struct proc_dir_entry *proc_net;
 extern struct proc_dir_entry *proc_bus;
 extern struct proc_dir_entry *proc_root_driver;
 extern struct proc_dir_entry *proc_root_kcore;
+extern struct proc_dir_entry *proc_vmcore;
 
 extern void proc_root_init(void);
 extern void proc_misc_init(void);
@@ -117,6 +118,7 @@ extern int proc_readdir(struct file *, v
 extern struct dentry *proc_lookup(struct inode *, struct dentry *, struct nameidata *);
 
 extern struct file_operations proc_kcore_operations;
+extern struct file_operations proc_vmcore_operations;
 extern struct file_operations proc_kmsg_operations;
 extern struct file_operations ppc_htab_operations;
 

_