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Subject[Patch 14/21] Create ELF header
Build the ELF header on the fly for the very first read request. The ELF Header,
Program Headers are stored in a buffer for processing future read() requests.

gencore-elf.c contains the ELF class specific functions.

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Signed-off-by: Ananth N.Mavinakayanahalli <ananth@in.ibm.com>

---
fs/proc/Makefile | 2
fs/proc/gencore-elf.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/proc/gencore.c | 5 +
fs/proc/gencore.h | 6 +
4 files changed, 189 insertions(+), 1 deletion(-)

Index: linux-2.6.36-rc7/fs/proc/gencore.h
===================================================================
--- linux-2.6.36-rc7.orig/fs/proc/gencore.h
+++ linux-2.6.36-rc7/fs/proc/gencore.h
@@ -7,6 +7,12 @@
struct core_proc {
struct list_head list;
struct task_struct *task;
+ void *shdr; /* elf_shdr, in case nphdrs > PN_XNUM */
+ char *elf_buf; /* buffer for elf_hdr + phdrs + notes */
+ size_t elf_buflen; /* size of elf_buf */
+ size_t nphdrs; /* number of phdrs */
};

+extern ssize_t elf_read_gencore(struct core_proc *cp, char __user *buffer,
+ size_t buflen, loff_t *foffset);
#endif
Index: linux-2.6.36-rc7/fs/proc/gencore-elf.c
===================================================================
--- /dev/null
+++ linux-2.6.36-rc7/fs/proc/gencore-elf.c
@@ -0,0 +1,177 @@
+/*
+ * Application core dump - ELF Class specific code
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2010
+ */
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/freezer.h>
+#include <linux/elf.h>
+#include <linux/elfcore.h>
+#include <linux/elfcore-internal.h>
+
+#ifdef CORE_DUMP_USE_REGSET
+#include <linux/regset.h>
+#endif
+
+#include "gencore.h"
+
+static void get_elfhdr_size(struct core_proc *cp)
+{
+ struct vm_area_struct *gate_vma;
+ int segs;
+
+ segs = cp->task->mm->map_count;
+ segs += elf_core_extra_phdrs();
+
+ gate_vma = get_gate_vma(cp->task);
+ if (gate_vma != NULL)
+ segs++;
+
+ /* One phdr for PT_NOTE */
+ segs++;
+
+ cp->nphdrs = segs;
+ cp->elf_buflen = sizeof(struct elfhdr) +
+ (cp->nphdrs * sizeof(struct elf_phdr));
+ cp->elf_buflen = roundup(cp->elf_buflen, ELF_EXEC_PAGESIZE);
+
+ return;
+}
+
+/*
+ * Fill the elf_hdr and the phdrs
+ * Returns 0 on success. On error, returns errno
+ */
+static int create_elf_header(struct core_proc *cp)
+{
+ struct elfhdr *elf = (struct elfhdr *)cp->elf_buf;
+ struct elf_phdr *note;
+ struct vm_area_struct *vma, *gate_vma = get_gate_vma(cp->task);
+ char *bufp;
+ off_t dataoff, offset;
+ short e_phnum = (cp->nphdrs > PN_XNUM ? PN_XNUM : cp->nphdrs);
+ size_t exphdrs_sz = 0;
+ unsigned long limit = elf_core_extra_phdrs() * sizeof(struct elf_phdr);
+
+#ifdef CORE_DUMP_USE_REGSET
+ const struct user_regset_view *view = task_user_regset_view(cp->task);
+
+ fill_elf_header(elf, e_phnum, view->e_machine, view->e_flags,
+ view->ei_osabi);
+#else
+ fill_elf_header(elf, e_phnum, ELF_ARCH, ELF_CORE_EFLAGS, ELF_OSABI);
+#endif
+ offset = sizeof(struct elfhdr);
+ bufp = cp->elf_buf + offset;
+ dataoff = offset + (cp->nphdrs * sizeof(struct elf_phdr));
+
+ /* Setup ELF PT_NOTE */
+ note = (struct elf_phdr*)bufp;
+ bufp += sizeof(struct elf_phdr);
+ offset += sizeof(struct elf_phdr);
+ note->p_type = PT_NOTE;
+ note->p_offset = dataoff;
+ note->p_vaddr = 0;
+ note->p_paddr = 0;
+ /* TODO: Needs to be populated with the size of the notes section */
+ note->p_memsz = 0;
+ note->p_flags = 0;
+ note->p_align = 0;
+
+ dataoff = cp->elf_buflen;
+
+ /* Write the phdrs for memory segments */
+ down_read(&cp->task->mm->mmap_sem);
+ for (vma = first_vma(cp->task, gate_vma); vma != NULL;
+ vma = next_vma(vma, gate_vma)) {
+ struct elf_phdr *phdr = (struct elf_phdr *)bufp;
+
+ bufp += sizeof(struct elf_phdr);
+ offset += sizeof(struct elf_phdr);
+
+ phdr->p_type = PT_LOAD;
+ phdr->p_offset = dataoff;
+ phdr->p_vaddr = vma->vm_start;
+ phdr->p_paddr = 0;
+ phdr->p_filesz = vma_dump_size(cp->task, vma, cp->task->mm->flags);
+ phdr->p_memsz = vma->vm_end - vma->vm_start;
+ phdr->p_flags = (vma->vm_flags & VM_READ) ? PF_R : 0;
+ if (vma->vm_flags & VM_WRITE)
+ phdr->p_flags |= PF_W;
+ if (vma->vm_flags & VM_EXEC)
+ phdr->p_flags |= PF_X;
+ phdr->p_align = ELF_EXEC_PAGESIZE;
+
+ dataoff += phdr->p_filesz;
+ }
+ up_read(&cp->task->mm->mmap_sem);
+
+ if (!elf_core_copy_extra_phdrs(bufp, dataoff, &exphdrs_sz, limit))
+ return -EIO;
+ bufp += exphdrs_sz;
+ dataoff += elf_core_extra_data_size();
+
+ if (e_phnum == PN_XNUM) {
+ cp->shdr = kzalloc(sizeof(struct elf_shdr), GFP_KERNEL);
+ if (!cp->shdr)
+ return -ENOMEM;
+ fill_extnum_info(elf, (struct elf_shdr *)cp->shdr,
+ dataoff, cp->nphdrs);
+ dataoff += sizeof(struct elf_shdr);
+ }
+
+ return 0;
+}
+
+ssize_t elf_read_gencore(struct core_proc *cp, char __user *buffer,
+ size_t buflen, loff_t *fpos)
+{
+ ssize_t ret = 0;
+
+ if (!cp->elf_buf) {
+ get_elfhdr_size(cp);
+
+ cp->elf_buf = kzalloc(cp->elf_buflen, GFP_KERNEL);
+ if (!cp->elf_buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ ret = create_elf_header(cp);
+ if (ret < 0)
+ goto out;
+ }
+
+ if (*fpos < cp->elf_buflen) {
+ size_t bcp = cp->elf_buflen - *fpos;
+
+ bcp = (bcp < buflen) ? bcp : buflen;
+ if (copy_to_user(buffer, (cp->elf_buf + *fpos), bcp)) {
+ ret = -EFAULT;
+ goto out;
+ } else {
+ ret = bcp;
+ *fpos += bcp;
+ buflen -= bcp;
+ buffer += bcp;
+ }
+ }
+
+out:
+ return ret;
+}
Index: linux-2.6.36-rc7/fs/proc/Makefile
===================================================================
--- linux-2.6.36-rc7.orig/fs/proc/Makefile
+++ linux-2.6.36-rc7/fs/proc/Makefile
@@ -19,7 +19,7 @@ proc-y += stat.o
proc-y += uptime.o
proc-y += version.o
proc-y += softirqs.o
-proc-$(CONFIG_ELF_CORE) += gencore.o
+proc-$(CONFIG_ELF_CORE) += gencore.o gencore-elf.o
proc-$(CONFIG_PROC_SYSCTL) += proc_sysctl.o
proc-$(CONFIG_NET) += proc_net.o
proc-$(CONFIG_PROC_KCORE) += kcore.o
Index: linux-2.6.36-rc7/fs/proc/gencore.c
===================================================================
--- linux-2.6.36-rc7.orig/fs/proc/gencore.c
+++ linux-2.6.36-rc7/fs/proc/gencore.c
@@ -63,6 +63,8 @@ static ssize_t read_gencore(struct file
}
mutex_unlock(&core_mutex);

+ ret = elf_read_gencore(cp, buffer, buflen, fpos);
+
out:
put_task_struct(task);
return ret;
@@ -89,6 +91,9 @@ static int release_gencore(struct inode
cp = get_core_proc(task);
if (cp) {
list_del(&cp->list);
+ if (cp->shdr)
+ kfree(cp->shdr);
+ kfree(cp->elf_buf);
kfree(cp);
}
mutex_unlock(&core_mutex);

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