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Subject[PATCH 01/41] introduction of regset ->get() wrappers, switching ELF coredumps to those
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Two new helpers: given a process and regset, dump into a buffer.
regset_get() takes a buffer and size, regset_get_alloc() takes size
and allocates a buffer.

Return value in both cases is the amount of data actually dumped in
case of success or -E... on error.

In both cases the size is capped by regset->n * regset->size, so
->get() is called with offset 0 and size no more than what regset
expects.

binfmt_elf.c callers of ->get() are switched to using those; the other
caller (copy_regset_to_user()) will need some preparations to switch.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/binfmt_elf.c | 54 ++++++++++++++++++++++++--------------------------
include/linux/regset.h | 9 +++++++++
kernel/Makefile | 2 +-
kernel/regset.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 90 insertions(+), 29 deletions(-)
create mode 100644 kernel/regset.c

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 9fe3b51c116a..80743b8957c9 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1821,7 +1821,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
long signr, size_t *total)
{
unsigned int i;
- unsigned int regset0_size = regset_size(t->task, &view->regsets[0]);
+ unsigned int regset0_size;

/*
* NT_PRSTATUS is the one special case, because the regset data
@@ -1830,8 +1830,10 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
* We assume that regset 0 is NT_PRSTATUS.
*/
fill_prstatus(&t->prstatus, t->task, signr);
- (void) view->regsets[0].get(t->task, &view->regsets[0], 0, regset0_size,
- &t->prstatus.pr_reg, NULL);
+ regset0_size = regset_get(t->task, &view->regsets[0],
+ sizeof(t->prstatus.pr_reg), &t->prstatus.pr_reg);
+ if (regset0_size < 0)
+ return 0;

fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
PRSTATUS_SIZE(t->prstatus, regset0_size), &t->prstatus);
@@ -1846,32 +1848,28 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
*/
for (i = 1; i < view->n; ++i) {
const struct user_regset *regset = &view->regsets[i];
+ int note_type = regset->core_note_type;
+ bool is_fpreg = note_type == NT_PRFPREG;
+ void *data;
+ int ret;
+
do_thread_regset_writeback(t->task, regset);
- if (regset->core_note_type && regset->get &&
- (!regset->active || regset->active(t->task, regset) > 0)) {
- int ret;
- size_t size = regset_size(t->task, regset);
- void *data = kzalloc(size, GFP_KERNEL);
- if (unlikely(!data))
- return 0;
- ret = regset->get(t->task, regset,
- 0, size, data, NULL);
- if (unlikely(ret))
- kfree(data);
- else {
- if (regset->core_note_type != NT_PRFPREG)
- fill_note(&t->notes[i], "LINUX",
- regset->core_note_type,
- size, data);
- else {
- SET_PR_FPVALID(&t->prstatus,
- 1, regset0_size);
- fill_note(&t->notes[i], "CORE",
- NT_PRFPREG, size, data);
- }
- *total += notesize(&t->notes[i]);
- }
- }
+ if (!note_type) // not for coredumps
+ continue;
+ if (regset->active && regset->active(t->task, regset) <= 0)
+ continue;
+
+ ret = regset_get_alloc(t->task, regset, ~0U, &data);
+ if (ret < 0)
+ continue;
+
+ if (is_fpreg)
+ SET_PR_FPVALID(&t->prstatus, 1, regset0_size);
+
+ fill_note(&t->notes[i], is_fpreg ? "CORE" : "LINUX",
+ note_type, ret, data);
+
+ *total += notesize(&t->notes[i]);
}

return 1;
diff --git a/include/linux/regset.h b/include/linux/regset.h
index 46d6ae68c455..968a032922d5 100644
--- a/include/linux/regset.h
+++ b/include/linux/regset.h
@@ -353,6 +353,15 @@ static inline int user_regset_copyin_ignore(unsigned int *pos,
return 0;
}

+extern int regset_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int size, void *data);
+
+extern int regset_get_alloc(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int size,
+ void **data);
+
/**
* copy_regset_to_user - fetch a thread's user_regset data into user memory
* @target: thread to be examined
diff --git a/kernel/Makefile b/kernel/Makefile
index f3218bc5ec69..e6e03380a0f1 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y = fork.o exec_domain.o panic.o \
extable.o params.o \
kthread.o sys_ni.o nsproxy.o \
notifier.o ksysfs.o cred.o reboot.o \
- async.o range.o smpboot.o ucount.o
+ async.o range.o smpboot.o ucount.o regset.o

obj-$(CONFIG_MODULES) += kmod.o
obj-$(CONFIG_MULTIUSER) += groups.o
diff --git a/kernel/regset.c b/kernel/regset.c
new file mode 100644
index 000000000000..6b39fa0993ec
--- /dev/null
+++ b/kernel/regset.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/regset.h>
+
+static int __regset_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int size,
+ void **data)
+{
+ void *p = *data, *to_free = NULL;
+ int res;
+
+ if (!regset->get)
+ return -EOPNOTSUPP;
+ if (size > regset->n * regset->size)
+ size = regset->n * regset->size;
+ if (!p) {
+ to_free = p = kzalloc(size, GFP_KERNEL);
+ if (!p)
+ return -ENOMEM;
+ }
+ res = regset->get(target, regset, 0, size, p, NULL);
+ if (unlikely(res < 0)) {
+ kfree(to_free);
+ return res;
+ }
+ *data = p;
+ if (regset->get_size) { // arm64-only kludge, will go away
+ unsigned max_size = regset->get_size(target, regset);
+ if (size > max_size)
+ size = max_size;
+ }
+ return size;
+}
+
+int regset_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int size,
+ void *data)
+{
+ return __regset_get(target, regset, size, &data);
+}
+EXPORT_SYMBOL(regset_get);
+
+int regset_get_alloc(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int size,
+ void **data)
+{
+ *data = NULL;
+ return __regset_get(target, regset, size, data);
+}
+EXPORT_SYMBOL(regset_get_alloc);
--
2.11.0
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