From d0f1088b31db2d03497a74ca67755df5515f8ff4 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 8 Mar 2020 09:16:37 -0400
Subject: [PATCH] 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>
---
arch/powerpc/platforms/cell/spufs/coredump.c | 3 +-
fs/binfmt_elf.c | 4 +-
fs/binfmt_elf_fdpic.c | 3 +-
fs/coredump.c | 72 ++++++++++++--------
include/linux/binfmts.h | 1 +
include/linux/coredump.h | 4 +-
6 files changed, 49 insertions(+), 38 deletions(-)
diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c
index 60b5583e9eafc..1a587618015c2 100644
--- 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 b12ba98ae9f55..187b3f2b9202a 100644
--- 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 3cfd6cd46f262..2c99b102c8600 100644
--- 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 1c0fdc1aa70b4..2868e3e171ae6 100644
--- 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 @@ void do_coredump(const kernel_siginfo_t *siginfo)
* 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;
}
@@ -914,32 +945,15 @@ 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.
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 0abd93efc1810..049cf9421d831 100644
--- 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 e58e8c2077828..247aae4e69c85 100644
--- 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,
--
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