[PATCH v4 18/39] unwind_user/sframe: Store sframe section data in per-mm maple tree

Josh Poimboeuf
2025-01-22T02:32:11Z

Associate an sframe section with its mm by adding it to a per-mm maple
tree which is indexed by the corresponding text address range. A single
sframe section can be associated with multiple text ranges.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/include/asm/mmu.h | 2 +-
include/linux/mm_types.h | 3 +++
include/linux/sframe.h | 13 +++++++++
kernel/fork.c | 10 +++++++
kernel/unwind/sframe.c | 55 +++++++++++++++++++++++++++++++++++---
mm/init-mm.c | 2 ++
6 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index ce4677b8b735..12ea831978cc 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -73,7 +73,7 @@ typedef struct {
.context = { \
.ctx_id = 1, \
.lock = __MUTEX_INITIALIZER(mm.context.lock), \
- }
+ },

void leave_mm(void);
#define leave_mm leave_mm
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 332cee285662..aba0d67fda9a 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1064,6 +1064,9 @@ struct mm_struct {
#endif
} lru_gen;
#endif /* CONFIG_LRU_GEN_WALKS_MMU */
+#ifdef CONFIG_HAVE_UNWIND_USER_SFRAME
+ struct maple_tree sframe_mt;
+#endif
} __randomize_layout;

/*
diff --git a/include/linux/sframe.h b/include/linux/sframe.h
index 3bfaf21869c2..ff4b9d1dbd00 100644
--- a/include/linux/sframe.h
+++ b/include/linux/sframe.h
@@ -22,14 +22,27 @@ struct sframe_section {
signed char fp_off;
};

+#define INIT_MM_SFRAME .sframe_mt = MTREE_INIT(sframe_mt, 0),
+extern void sframe_free_mm(struct mm_struct *mm);
+
extern int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
unsigned long text_start, unsigned long text_end);
extern int sframe_remove_section(unsigned long sframe_addr);

+static inline bool current_has_sframe(void)
+{
+ struct mm_struct *mm = current->mm;
+
+ return mm && !mtree_empty(&mm->sframe_mt);
+}
+
#else /* !CONFIG_HAVE_UNWIND_USER_SFRAME */

+#define INIT_MM_SFRAME
+static inline void sframe_free_mm(struct mm_struct *mm) {}
static inline int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end, unsigned long text_start, unsigned long text_end) { return -ENOSYS; }
static inline int sframe_remove_section(unsigned long sframe_addr) { return -ENOSYS; }
+static inline bool current_has_sframe(void) { return false; }

#endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */

diff --git a/kernel/fork.c b/kernel/fork.c
index 9b301180fd41..88753f8bbdd3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -105,6 +105,7 @@
#include <uapi/linux/pidfd.h>
#include <linux/pidfs.h>
#include <linux/tick.h>
+#include <linux/sframe.h>

#include <asm/pgalloc.h>
#include <linux/uaccess.h>
@@ -925,6 +926,7 @@ void __mmdrop(struct mm_struct *mm)
mm_pasid_drop(mm);
mm_destroy_cid(mm);
percpu_counter_destroy_many(mm->rss_stat, NR_MM_COUNTERS);
+ sframe_free_mm(mm);

free_mm(mm);
}
@@ -1252,6 +1254,13 @@ static void mm_init_uprobes_state(struct mm_struct *mm)
#endif
}

+static void mm_init_sframe(struct mm_struct *mm)
+{
+#ifdef CONFIG_HAVE_UNWIND_USER_SFRAME
+ mt_init(&mm->sframe_mt);
+#endif
+}
+
static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
struct user_namespace *user_ns)
{
@@ -1283,6 +1292,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm->pmd_huge_pte = NULL;
#endif
mm_init_uprobes_state(mm);
+ mm_init_sframe(mm);
hugetlb_count_init(mm);

if (current->mm) {
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
index 20287f795b36..fa7d87ffd00a 100644
--- a/kernel/unwind/sframe.c
+++ b/kernel/unwind/sframe.c
@@ -122,15 +122,64 @@ int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end,
if (ret)
goto err_free;

- /* TODO nowhere to store it yet - just free it and return an error */
- ret = -ENOSYS;
+ ret = mtree_insert_range(sframe_mt, sec->text_start, sec->text_end, sec, GFP_KERNEL);
+ if (ret) {
+ dbg("mtree_insert_range failed: text=%lx-%lx\n",
+ sec->text_start, sec->text_end);
+ goto err_free;
+ }
+
+ return 0;

err_free:
free_section(sec);
return ret;
}

+static int __sframe_remove_section(struct mm_struct *mm,
+ struct sframe_section *sec)
+{
+ if (!mtree_erase(&mm->sframe_mt, sec->text_start)) {
+ dbg("mtree_erase failed: text=%lx\n", sec->text_start);
+ return -EINVAL;
+ }
+
+ free_section(sec);
+
+ return 0;
+}
+
int sframe_remove_section(unsigned long sframe_start)
{
- return -ENOSYS;
+ struct mm_struct *mm = current->mm;
+ struct sframe_section *sec;
+ unsigned long index = 0;
+ bool found = false;
+ int ret = 0;
+
+ mt_for_each(&mm->sframe_mt, sec, index, ULONG_MAX) {
+ if (sec->sframe_start == sframe_start) {
+ found = true;
+ ret |= __sframe_remove_section(mm, sec);
+ }
+ }
+
+ if (!found || ret)
+ return -EINVAL;
+
+ return 0;
+}
+
+void sframe_free_mm(struct mm_struct *mm)
+{
+ struct sframe_section *sec;
+ unsigned long index = 0;
+
+ if (!mm)
+ return;
+
+ mt_for_each(&mm->sframe_mt, sec, index, ULONG_MAX)
+ free_section(sec);
+
+ mtree_destroy(&mm->sframe_mt);
}
diff --git a/mm/init-mm.c b/mm/init-mm.c
index 24c809379274..feb01fcd32f0 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -11,6 +11,7 @@
#include <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/iommu.h>
+#include <linux/sframe.h>
#include <asm/mmu.h>

#ifndef INIT_MM_CONTEXT
@@ -45,6 +46,7 @@ struct mm_struct init_mm = {
.user_ns = &init_user_ns,
.cpu_bitmap = CPU_BITS_NONE,
INIT_MM_CONTEXT(init_mm)
+ INIT_MM_SFRAME
};

void setup_initial_init_mm(void *start_code, void *end_code,
--
2.48.1