[Linux-ia64] Re: [PATCH] head.S fix for unusual load addrs

["Luck, Tony" <tony.luck@intel.com>]

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Here's a first crack at the missing fs/proc/kcore.c
part of relocating the kernel.

Not as pretty as I'd hoped ... just having your kernel
at a lower address than your modules isn't sufficient
to fit with what the code currently does (which is to
assume that your kernel is in the 1-1 area above
PAGE_OFFSET).

Perhaps it might be cleaner to add the kernel to the
vmlist (as somebody suggested before)?  That would get
rid of almost all the changes except one ... we'd still
need to set KCORE_BASE to the start address of region 5,
so any suggestions on how to do that in a cleaner way
than #ifdef CONFIG_IA64 gratefully accepted.

-Tony


[-- Attachment #2: kcore.c --]
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/*
 *	fs/proc/kcore.c kernel ELF/AOUT core dumper
 *
 *	Modelled on fs/exec.c:aout_core_dump()
 *	Jeremy Fitzhardinge <jeremy@sw.oz.au>
 *	ELF version written by David Howells <David.Howells@nexor.co.uk>
 *	Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
 *	Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
 *	Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
 */

#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/highmem.h>
#include <asm/uaccess.h>
#include <asm/io.h>


static int open_kcore(struct inode * inode, struct file * filp)
{
	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

static ssize_t read_kcore(struct file *, char *, size_t, loff_t *);

struct file_operations proc_kcore_operations = {
	read:		read_kcore,
	open:		open_kcore,
};

#ifdef CONFIG_KCORE_AOUT
static ssize_t read_kcore(struct file *file, char *buf, size_t count, loff_t *ppos)
{
	unsigned long long p = *ppos, memsize;
	ssize_t read;
	ssize_t count1;
	char * pnt;
	struct user dump;
#if defined (__i386__) || defined (__mc68000__) || defined(__x86_64__)
#	define FIRST_MAPPED	PAGE_SIZE	/* we don't have page 0 mapped on x86.. */
#else
#	define FIRST_MAPPED	0
#endif

	memset(&dump, 0, sizeof(struct user));
	dump.magic = CMAGIC;
	dump.u_dsize = (virt_to_phys(high_memory) >> PAGE_SHIFT);
#if defined (__i386__) || defined(__x86_64__)
	dump.start_code = PAGE_OFFSET;
#endif
#ifdef __alpha__
	dump.start_data = PAGE_OFFSET;
#endif

	memsize = virt_to_phys(high_memory);
	if (p >= memsize)
		return 0;
	if (count > memsize - p)
		count = memsize - p;
	read = 0;

	if (p < sizeof(struct user) && count > 0) {
		count1 = count;
		if (p + count1 > sizeof(struct user))
			count1 = sizeof(struct user)-p;
		pnt = (char *) &dump + p;
		if (copy_to_user(buf,(void *) pnt, count1))
			return -EFAULT;
		buf += count1;
		p += count1;
		count -= count1;
		read += count1;
	}

	if (count > 0 && p < PAGE_SIZE + FIRST_MAPPED) {
		count1 = PAGE_SIZE + FIRST_MAPPED - p;
		if (count1 > count)
			count1 = count;
		if (clear_user(buf, count1))
			return -EFAULT;
		buf += count1;
		p += count1;
		count -= count1;
		read += count1;
	}
	if (count > 0) {
		if (copy_to_user(buf, (void *) (PAGE_OFFSET+p-PAGE_SIZE), count))
			return -EFAULT;
		read += count;
	}
	*ppos += read;
	return read;
}
#else /* CONFIG_KCORE_AOUT */

#define roundup(x, y)  ((((x)+((y)-1))/(y))*(y))

/* An ELF note in memory */
struct memelfnote
{
	const char *name;
	int type;
	unsigned int datasz;
	void *data;
};

extern char saved_command_line[];

static size_t get_kcore_size(int *num_vma, size_t *elf_buflen)
{
	size_t try, size;
	struct vm_struct *m;

	*num_vma = 0;
	size = ((size_t)high_memory - PAGE_OFFSET + PAGE_SIZE);
	if (!vmlist) {
		*elf_buflen = PAGE_SIZE;
		return (size);
	}

	for (m=vmlist; m; m=m->next) {
		try = (size_t)m->addr + m->size;
		if (try > size)
			size = try;
		*num_vma = *num_vma + 1;
	}
	*elf_buflen =	sizeof(struct elfhdr) + 
			(*num_vma + 2)*sizeof(struct elf_phdr) + 
			3 * sizeof(struct memelfnote);
	*elf_buflen = PAGE_ALIGN(*elf_buflen);
	return (size - PAGE_OFFSET + *elf_buflen);
}


/*****************************************************************************/
/*
 * determine size of ELF note
 */
static int notesize(struct memelfnote *en)
{
	int sz;

	sz = sizeof(struct elf_note);
	sz += roundup(strlen(en->name), 4);
	sz += roundup(en->datasz, 4);

	return sz;
} /* end notesize() */

/*****************************************************************************/
/*
 * store a note in the header buffer
 */
static char *storenote(struct memelfnote *men, char *bufp)
{
	struct elf_note en;

#define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0)

	en.n_namesz = strlen(men->name);
	en.n_descsz = men->datasz;
	en.n_type = men->type;

	DUMP_WRITE(&en, sizeof(en));
	DUMP_WRITE(men->name, en.n_namesz);

	/* XXX - cast from long long to long to avoid need for libgcc.a */
	bufp = (char*) roundup((unsigned long)bufp,4);
	DUMP_WRITE(men->data, men->datasz);
	bufp = (char*) roundup((unsigned long)bufp,4);

#undef DUMP_WRITE

	return bufp;
} /* end storenote() */

/*
 * store an ELF coredump header in the supplied buffer
 * num_vma is the number of elements in vmlist
 */
static void elf_kcore_store_hdr(char *bufp, int num_vma, int dataoff)
{
	struct elf_prstatus prstatus;	/* NT_PRSTATUS */
	struct elf_prpsinfo prpsinfo;	/* NT_PRPSINFO */
	struct elf_phdr *nhdr, *phdr;
	struct elfhdr *elf;
	struct memelfnote notes[3];
	off_t offset = 0;
	struct vm_struct *m;

	/* setup ELF header */
	elf = (struct elfhdr *) bufp;
	bufp += sizeof(struct elfhdr);
	offset += sizeof(struct elfhdr);
	memcpy(elf->e_ident, ELFMAG, SELFMAG);
	elf->e_ident[EI_CLASS]	= ELF_CLASS;
	elf->e_ident[EI_DATA]	= ELF_DATA;
	elf->e_ident[EI_VERSION]= EV_CURRENT;
	memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD);
	elf->e_type	= ET_CORE;
	elf->e_machine	= ELF_ARCH;
	elf->e_version	= EV_CURRENT;
	elf->e_entry	= 0;
	elf->e_phoff	= sizeof(struct elfhdr);
	elf->e_shoff	= 0;
	elf->e_flags	= 0;
	elf->e_ehsize	= sizeof(struct elfhdr);
	elf->e_phentsize= sizeof(struct elf_phdr);
	elf->e_phnum	= 2 + num_vma;
	elf->e_shentsize= 0;
	elf->e_shnum	= 0;
	elf->e_shstrndx	= 0;

	/* setup ELF PT_NOTE program header */
	nhdr = (struct elf_phdr *) bufp;
	bufp += sizeof(struct elf_phdr);
	offset += sizeof(struct elf_phdr);
	nhdr->p_type	= PT_NOTE;
	nhdr->p_offset	= 0;
	nhdr->p_vaddr	= 0;
	nhdr->p_paddr	= 0;
	nhdr->p_filesz	= 0;
	nhdr->p_memsz	= 0;
	nhdr->p_flags	= 0;
	nhdr->p_align	= 0;

	/* setup ELF PT_LOAD program header for the 
	 * virtual range 0xc0000000 -> high_memory */
	phdr = (struct elf_phdr *) bufp;
	bufp += sizeof(struct elf_phdr);
	offset += sizeof(struct elf_phdr);
	phdr->p_type	= PT_LOAD;
	phdr->p_flags	= PF_R|PF_W|PF_X;
	phdr->p_offset	= dataoff;
	phdr->p_vaddr	= PAGE_OFFSET;
	phdr->p_paddr	= __pa(PAGE_OFFSET);
	phdr->p_filesz	= phdr->p_memsz = ((unsigned long)high_memory - PAGE_OFFSET);
	phdr->p_align	= PAGE_SIZE;

	/* setup ELF PT_LOAD program header for every vmalloc'd area */
	for (m=vmlist; m; m=m->next) {
		if (m->flags & VM_IOREMAP) /* don't dump ioremap'd stuff! (TA) */
			continue;

		phdr = (struct elf_phdr *) bufp;
		bufp += sizeof(struct elf_phdr);
		offset += sizeof(struct elf_phdr);

		phdr->p_type	= PT_LOAD;
		phdr->p_flags	= PF_R|PF_W|PF_X;
		phdr->p_offset	= (size_t)m->addr - PAGE_OFFSET + dataoff;
		phdr->p_vaddr	= (size_t)m->addr;
		phdr->p_paddr	= __pa(m->addr);
		phdr->p_filesz	= phdr->p_memsz	= m->size;
		phdr->p_align	= PAGE_SIZE;
	}

	/*
	 * Set up the notes in similar form to SVR4 core dumps made
	 * with info from their /proc.
	 */
	nhdr->p_offset	= offset;

	/* 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));

	nhdr->p_filesz	= notesize(&notes[0]);
	bufp = storenote(&notes[0], bufp);

	/* set up the process info */
	notes[1].name	= "CORE";
	notes[1].type	= NT_PRPSINFO;
	notes[1].datasz	= sizeof(struct elf_prpsinfo);
	notes[1].data	= &prpsinfo;

	memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo));
	prpsinfo.pr_state	= 0;
	prpsinfo.pr_sname	= 'R';
	prpsinfo.pr_zomb	= 0;

	strcpy(prpsinfo.pr_fname, "vmlinux");
	strncpy(prpsinfo.pr_psargs, saved_command_line, ELF_PRARGSZ);

	nhdr->p_filesz	= notesize(&notes[1]);
	bufp = storenote(&notes[1], bufp);

	/* set up the task structure */
	notes[2].name	= "CORE";
	notes[2].type	= NT_TASKSTRUCT;
	notes[2].datasz	= sizeof(struct task_struct);
	notes[2].data	= current;

	nhdr->p_filesz	= notesize(&notes[2]);
	bufp = storenote(&notes[2], bufp);

} /* end elf_kcore_store_hdr() */

/*****************************************************************************/
/*
 * read from the ELF header and then kernel memory
 */
static ssize_t read_kcore(struct file *file, char *buffer, size_t buflen, loff_t *fpos)
{
	ssize_t acc = 0;
	size_t size, tsz;
	size_t elf_buflen;
	int num_vma;
	unsigned long start;

	read_lock(&vmlist_lock);
	proc_root_kcore->size = size = get_kcore_size(&num_vma, &elf_buflen);
	if (buflen == 0 || *fpos >= size) {
		read_unlock(&vmlist_lock);
		return 0;
	}

	/* 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) {
			read_unlock(&vmlist_lock);
			return -ENOMEM;
		}
		memset(elf_buf, 0, elf_buflen);
		elf_kcore_store_hdr(elf_buf, num_vma, elf_buflen);
		read_unlock(&vmlist_lock);
		if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
			kfree(elf_buf);
			return -EFAULT;
		}
		kfree(elf_buf);
		buflen -= tsz;
		*fpos += tsz;
		buffer += tsz;
		acc += tsz;

		/* leave now if filled buffer already */
		if (buflen == 0)
			return acc;
	} else
		read_unlock(&vmlist_lock);

	/* where page 0 not mapped, write zeros into buffer */
#if defined (__i386__) || defined (__mc68000__) || defined(__x86_64__)
	if (*fpos < PAGE_SIZE + elf_buflen) {
		/* work out how much to clear */
		tsz = PAGE_SIZE + elf_buflen - *fpos;
		if (buflen < tsz)
			tsz = buflen;

		/* write zeros to buffer */
		if (clear_user(buffer, tsz))
			return -EFAULT;
		buflen -= tsz;
		*fpos += tsz;
		buffer += tsz;
		acc += tsz;

		/* leave now if filled buffer already */
		if (buflen == 0)
			return tsz;
	}
#endif
	
	/*
	 * Fill the remainder of the buffer from kernel VM space.
	 * We said in the ELF header that the data which starts
	 * at 'elf_buflen' is virtual address PAGE_OFFSET. --rmk
	 */
	start = PAGE_OFFSET + (*fpos - elf_buflen);
	if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
		tsz = buflen;
		
	while (buflen) {
		if ((start >= VMALLOC_START) && (start < VMALLOC_END)) {
			char * elf_buf;
			struct vm_struct *m;
			unsigned long curstart = start;
			unsigned long cursize = tsz;

			elf_buf = kmalloc(tsz, GFP_KERNEL);
			if (!elf_buf)
				return -ENOMEM;
			memset(elf_buf, 0, tsz);

			read_lock(&vmlist_lock);
			for (m=vmlist; m && cursize; m=m->next) {
				unsigned long vmstart;
				unsigned long vmsize;
				unsigned long msize = m->size - PAGE_SIZE;

				if (((unsigned long)m->addr + msize) < 
								curstart)
					continue;
				if ((unsigned long)m->addr > (curstart + 
								cursize))
					break;
				vmstart = (curstart < (unsigned long)m->addr ? 
					(unsigned long)m->addr : curstart);
				if (((unsigned long)m->addr + msize) > 
							(curstart + cursize))
					vmsize = curstart + cursize - vmstart;
				else
					vmsize = (unsigned long)m->addr + 
							msize - vmstart;
				curstart = vmstart + vmsize;
				cursize -= vmsize;
				/* don't dump ioremap'd stuff! (TA) */
				if (m->flags & VM_IOREMAP)
					continue;
				memcpy(elf_buf + (vmstart - start),
					(char *)vmstart, vmsize);
			}
			read_unlock(&vmlist_lock);
			if (copy_to_user(buffer, elf_buf, tsz)) {
				kfree(elf_buf);
				return -EFAULT;
			}
			kfree(elf_buf);
		} else if ((start > PAGE_OFFSET) && (start < 
						(unsigned long)high_memory)) {
			if (kern_addr_valid(start)) {
				if (copy_to_user(buffer, (char *)start, tsz))
					return -EFAULT;
			} else {
				if (clear_user(buffer, tsz))
					return -EFAULT;
			}
		} else {
			if (clear_user(buffer, tsz))
				return -EFAULT;
		}
		buflen -= tsz;
		*fpos += tsz;
		buffer += tsz;
		acc += tsz;
		start += tsz;
		tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
	}

	return acc;
}
#endif /* CONFIG_KCORE_AOUT */