elf core dump: notes user_regset

This modifies the ELF core dump code under #ifdef CORE_DUMP_USE_REGSET.
It changes nothing when this macro is not defined.  When it's #define'd
by some arch header (e.g. asm/elf.h), the arch must support the
user_regset (linux/regset.h) interface for reading thread state.

This provides an alternate version of note segment writing that is based
purely on the user_regset interfaces.  When CORE_DUMP_USE_REGSET is set,
the arch need not define macros such as ELF_CORE_COPY_REGS and ELF_ARCH.
All that information is taken from the user_regset data structures.
The core dumps come out exactly the same if arch's definitions for its
user_regset details are correct.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 224 insertions, 0 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 4510429b973e..786ee275ec0a 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1528,6 +1528,228 @@ static void fill_auxv_note(struct memelfnote *note, struct mm_struct *mm)
         fill_note(note, "CORE", NT_AUXV, i * sizeof(elf_addr_t), auxv);
 }
 
+#ifdef CORE_DUMP_USE_REGSET
+#include <linux/regset.h>
+
+struct elf_thread_core_info {
+        struct elf_thread_core_info *next;
+        struct task_struct *task;
+        struct elf_prstatus prstatus;
+        struct memelfnote notes[0];
+};
+
+struct elf_note_info {
+        struct elf_thread_core_info *thread;
+        struct memelfnote psinfo;
+        struct memelfnote auxv;
+        size_t size;
+        int thread_notes;
+};
+
+static int fill_thread_core_info(struct elf_thread_core_info *t,
+                                 const struct user_regset_view *view,
+                                 long signr, size_t *total)
+{
+        unsigned int i;
+
+        /*
+         * NT_PRSTATUS is the one special case, because the regset data
+         * goes into the pr_reg field inside the note contents, rather
+         * than being the whole note contents.  We fill the reset in here.
+         * 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, sizeof(t->prstatus.pr_reg),
+                                    &t->prstatus.pr_reg, NULL);
+
+        fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
+                  sizeof(t->prstatus), &t->prstatus);
+        *total += notesize(&t->notes[0]);
+
+        /*
+         * Each other regset might generate a note too.  For each regset
+         * that has no core_note_type or is inactive, we leave t->notes[i]
+         * all zero and we'll know to skip writing it later.
+         */
+        for (i = 1; i < view->n; ++i) {
+                const struct user_regset *regset = &view->regsets[i];
+                if (regset->core_note_type &&
+                    (!regset->active || regset->active(t->task, regset))) {
+                        int ret;
+                        size_t size = regset->n * regset->size;
+                        void *data = kmalloc(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 {
+                                        t->prstatus.pr_fpvalid = 1;
+                                        fill_note(&t->notes[i], "CORE",
+                                                  NT_PRFPREG, size, data);
+                                }
+                                *total += notesize(&t->notes[i]);
+                        }
+                }
+        }
+
+        return 1;
+}
+
+static int fill_note_info(struct elfhdr *elf, int phdrs,
+                          struct elf_note_info *info,
+                          long signr, struct pt_regs *regs)
+{
+        struct task_struct *dump_task = current;
+        const struct user_regset_view *view = task_user_regset_view(dump_task);
+        struct elf_thread_core_info *t;
+        struct elf_prpsinfo *psinfo;
+        struct task_struct *g, *p;
+        unsigned int i;
+
+        info->size = 0;
+        info->thread = NULL;
+
+        psinfo = kmalloc(sizeof(*psinfo), GFP_KERNEL);
+        fill_note(&info->psinfo, "CORE", NT_PRPSINFO, sizeof(*psinfo), psinfo);
+
+        if (psinfo == NULL)
+                return 0;
+
+        /*
+         * Figure out how many notes we're going to need for each thread.
+         */
+        info->thread_notes = 0;
+        for (i = 0; i < view->n; ++i)
+                if (view->regsets[i].core_note_type != 0)
+                        ++info->thread_notes;
+
+        /*
+         * Sanity check.  We rely on regset 0 being in NT_PRSTATUS,
+         * since it is our one special case.
+         */
+        if (unlikely(info->thread_notes == 0) ||
+            unlikely(view->regsets[0].core_note_type != NT_PRSTATUS)) {
+                WARN_ON(1);
+                return 0;
+        }
+
+        /*
+         * Initialize the ELF file header.
+         */
+        fill_elf_header(elf, phdrs,
+                        view->e_machine, view->e_flags, view->ei_osabi);
+
+        /*
+         * Allocate a structure for each thread.
+         */
+        rcu_read_lock();
+        do_each_thread(g, p)
+                if (p->mm == dump_task->mm) {
+                        t = kzalloc(offsetof(struct elf_thread_core_info,
+                                             notes[info->thread_notes]),
+                                    GFP_ATOMIC);
+                        if (unlikely(!t)) {
+                                rcu_read_unlock();
+                                return 0;
+                        }
+                        t->task = p;
+                        if (p == dump_task || !info->thread) {
+                                t->next = info->thread;
+                                info->thread = t;
+                        } else {
+                                /*
+                                 * Make sure to keep the original task at
+                                 * the head of the list.
+                                 */
+                                t->next = info->thread->next;
+                                info->thread->next = t;
+                        }
+                }
+        while_each_thread(g, p);
+        rcu_read_unlock();
+
+        /*
+         * Now fill in each thread's information.
+         */
+        for (t = info->thread; t != NULL; t = t->next)
+                if (!fill_thread_core_info(t, view, signr, &info->size))
+                        return 0;
+
+        /*
+         * Fill in the two process-wide notes.
+         */
+        fill_psinfo(psinfo, dump_task->group_leader, dump_task->mm);
+        info->size += notesize(&info->psinfo);
+
+        fill_auxv_note(&info->auxv, current->mm);
+        info->size += notesize(&info->auxv);
+
+        return 1;
+}
+
+static size_t get_note_info_size(struct elf_note_info *info)
+{
+        return info->size;
+}
+
+/*
+ * Write all the notes for each thread.  When writing the first thread, the
+ * process-wide notes are interleaved after the first thread-specific note.
+ */
+static int write_note_info(struct elf_note_info *info,
+                           struct file *file, loff_t *foffset)
+{
+        bool first = 1;
+        struct elf_thread_core_info *t = info->thread;
+
+        do {
+                int i;
+
+                if (!writenote(&t->notes[0], file, foffset))
+                        return 0;
+
+                if (first && !writenote(&info->psinfo, file, foffset))
+                        return 0;
+                if (first && !writenote(&info->auxv, file, foffset))
+                        return 0;
+
+                for (i = 1; i < info->thread_notes; ++i)
+                        if (t->notes[i].data &&
+                            !writenote(&t->notes[i], file, foffset))
+                                return 0;
+
+                first = 0;
+                t = t->next;
+        } while (t);
+
+        return 1;
+}
+
+static void free_note_info(struct elf_note_info *info)
+{
+        struct elf_thread_core_info *threads = info->thread;
+        while (threads) {
+                unsigned int i;
+                struct elf_thread_core_info *t = threads;
+                threads = t->next;
+                WARN_ON(t->notes[0].data && t->notes[0].data != &t->prstatus);
+                for (i = 1; i < info->thread_notes; ++i)
+                        kfree(t->notes[i].data);
+                kfree(t);
+        }
+        kfree(info->psinfo.data);
+}
+
+#else
+
 /* Here is the structure in which status of each thread is captured. */
 struct elf_thread_status
 {
@@ -1748,6 +1970,8 @@ static void free_note_info(struct elf_note_info *info)
 #endif
 }
 
+#endif
+
 static struct vm_area_struct *first_vma(struct task_struct *tsk,
                                         struct vm_area_struct *gate_vma)
 {