coredump: don't bother with do_truncate()

have dump_skip() just remember how much needs to be skipped,
leave actual seeks/writing zeroes to the next dump_emit()
or the end of coredump output, whichever comes first.
And instead of playing with do_truncate() in the end, just
write one NUL at the end of the last gap (if any).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c
index 60b5583..1a58761 100644 (file)
--- a/arch/powerpc/platforms/cell/spufs/coredump.c
+++ b/arch/powerpc/platforms/cell/spufs/coredump.c
@@ -149,8 +149,7 @@ static int spufs_arch_write_note(struct spu_context *ctx, int i,
                        return -EIO;
        }
 
-       if (!dump_skip(cprm, roundup(cprm->pos - ret + sz, 4) - cprm->pos))
-               return -EIO;
+       dump_skip_to(cprm, roundup(cprm->pos - ret + sz, 4));
        return 0;
 }
 

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index b12ba98..187b3f2 100644 (file)
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2267,8 +2267,7 @@ static int elf_core_dump(struct coredump_params *cprm)
                goto end_coredump;
 
        /* Align to page */
-       if (!dump_skip(cprm, dataoff - cprm->pos))
-               goto end_coredump;
+       dump_skip_to(cprm, dataoff);
 
        for (i = 0; i < vma_count; i++) {
                struct core_vma_metadata *meta = vma_meta + i;
@@ -2276,7 +2275,6 @@ static int elf_core_dump(struct coredump_params *cprm)
                if (!dump_user_range(cprm, meta->start, meta->dump_size))
                        goto end_coredump;
        }
-       dump_truncate(cprm);
 
        if (!elf_core_write_extra_data(cprm))
                goto end_coredump;

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 3cfd6cd..2c99b10 100644 (file)
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1631,8 +1631,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
                                goto end_coredump;
        }
 
-       if (!dump_skip(cprm, dataoff - cprm->pos))
-               goto end_coredump;
+       dump_skip_to(cprm, dataoff);
 
        if (!elf_fdpic_dump_segments(cprm, vma_meta, vma_count))
                goto end_coredump;

diff --git a/fs/coredump.c b/fs/coredump.c
index 1c0fdc1..2868e3e 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -809,6 +809,16 @@ void do_coredump(const kernel_siginfo_t *siginfo)
                }
                file_start_write(cprm.file);
                core_dumped = binfmt->core_dump(&cprm);
+               /*
+                * Ensures that file size is big enough to contain the current
+                * file postion. This prevents gdb from complaining about
+                * a truncated file if the last "write" to the file was
+                * dump_skip.
+                */
+               if (cprm.to_skip) {
+                       cprm.to_skip--;
+                       dump_emit(&cprm, "", 1);
+               }
                file_end_write(cprm.file);
        }
        if (ispipe && core_pipe_limit)
@@ -835,7 +845,7 @@ fail:
  * do on a core-file: use only these functions to write out all the
  * necessary info.
  */
-int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
+static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 {
        struct file *file = cprm->file;
        loff_t pos = file->f_pos;
@@ -855,9 +865,8 @@ int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
 
        return 1;
 }
-EXPORT_SYMBOL(dump_emit);
 
-int dump_skip(struct coredump_params *cprm, size_t nr)
+static int __dump_skip(struct coredump_params *cprm, size_t nr)
 {
        static char zeroes[PAGE_SIZE];
        struct file *file = cprm->file;
@@ -869,13 +878,35 @@ int dump_skip(struct coredump_params *cprm, size_t nr)
                return 1;
        } else {
                while (nr > PAGE_SIZE) {
-                       if (!dump_emit(cprm, zeroes, PAGE_SIZE))
+                       if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
                                return 0;
                        nr -= PAGE_SIZE;
                }
-               return dump_emit(cprm, zeroes, nr);
+               return __dump_emit(cprm, zeroes, nr);
        }
 }
+
+int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
+{
+       if (cprm->to_skip) {
+               if (!__dump_skip(cprm, cprm->to_skip))
+                       return 0;
+               cprm->to_skip = 0;
+       }
+       return __dump_emit(cprm, addr, nr);
+}
+EXPORT_SYMBOL(dump_emit);
+
+void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
+{
+       cprm->to_skip = pos - cprm->pos;
+}
+EXPORT_SYMBOL(dump_skip_to);
+
+void dump_skip(struct coredump_params *cprm, size_t nr)
+{
+       cprm->to_skip += nr;
+}
 EXPORT_SYMBOL(dump_skip);
 
 #ifdef CONFIG_ELF_CORE
@@ -902,11 +933,11 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
                        stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
                        kunmap_local(kaddr);
                        put_page(page);
+                       if (stop)
+                               return 0;
                } else {
-                       stop = !dump_skip(cprm, PAGE_SIZE);
+                       dump_skip(cprm, PAGE_SIZE);
                }
-               if (stop)
-                       return 0;
        }
        return 1;
 }
@@ -914,33 +945,16 @@ int dump_user_range(struct coredump_params *cprm, unsigned long start,
 
 int dump_align(struct coredump_params *cprm, int align)
 {
-       unsigned mod = cprm->pos & (align - 1);
+       unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
        if (align & (align - 1))
                return 0;
-       return mod ? dump_skip(cprm, align - mod) : 1;
+       if (mod)
+               cprm->to_skip += align - mod;
+       return 1;
 }
 EXPORT_SYMBOL(dump_align);
 
 /*
- * Ensures that file size is big enough to contain the current file
- * postion. This prevents gdb from complaining about a truncated file
- * if the last "write" to the file was dump_skip.
- */
-void dump_truncate(struct coredump_params *cprm)
-{
-       struct file *file = cprm->file;
-       loff_t offset;
-
-       if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
-               offset = file->f_op->llseek(file, 0, SEEK_CUR);
-               if (i_size_read(file->f_mapping->host) < offset)
-                       do_truncate(file_mnt_user_ns(file), file->f_path.dentry,
-                                   offset, 0, file);
-       }
-}
-EXPORT_SYMBOL(dump_truncate);
-
-/*
  * The purpose of always_dump_vma() is to make sure that special kernel mappings
  * that are useful for post-mortem analysis are included in every core dump.
  * In that way we ensure that the core dump is fully interpretable later

diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 0abd93e..049cf94 100644 (file)
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -86,6 +86,7 @@ struct coredump_params {
        unsigned long mm_flags;
        loff_t written;
        loff_t pos;
+       loff_t to_skip;
 };
 
 /*

diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index e58e8c2..247aae4 100644 (file)
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -18,10 +18,10 @@ struct core_vma_metadata {
  * functions to write out all the necessary info.
  */
 struct coredump_params;
-extern int dump_skip(struct coredump_params *cprm, size_t nr);
+extern void dump_skip_to(struct coredump_params *cprm, unsigned long to);
+extern void dump_skip(struct coredump_params *cprm, size_t nr);
 extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
 extern int dump_align(struct coredump_params *cprm, int align);
-extern void dump_truncate(struct coredump_params *cprm);
 int dump_user_range(struct coredump_params *cprm, unsigned long start,
                    unsigned long len);
 int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,