Thread (49 messages) 49 messages, 7 authors, 2023-11-07

Re: [PATCH v3 06/13] mm/execmem: introduce execmem_data_alloc()

From: Song Liu <song@kernel.org>
Date: 2023-09-21 22:52:39
Also in: bpf, linux-arm-kernel, linux-mips, linux-mm, linux-modules, linux-riscv, linux-s390, linux-trace-kernel, linuxppc-dev, lkml, loongarch, sparclinux

On Mon, Sep 18, 2023 at 12:31 AM Mike Rapoport [off-list ref] wrote:
[...]
quoted hunk ↗ jump to hunk
diff --git a/include/linux/execmem.h b/include/linux/execmem.h
index 519bdfdca595..09d45ac786e9 100644
--- a/include/linux/execmem.h
+++ b/include/linux/execmem.h
@@ -29,6 +29,7 @@
  * @EXECMEM_KPROBES: parameters for kprobes
  * @EXECMEM_FTRACE: parameters for ftrace
  * @EXECMEM_BPF: parameters for BPF
+ * @EXECMEM_MODULE_DATA: parameters for module data sections
  * @EXECMEM_TYPE_MAX:
  */
 enum execmem_type {
@@ -37,6 +38,7 @@ enum execmem_type {
        EXECMEM_KPROBES,
        EXECMEM_FTRACE,
In longer term, I think we can improve the JITed code and merge
kprobe/ftrace/bpf. to use the same ranges. Also, do we need special
setting for FTRACE? If not, let's just remove it.
        EXECMEM_BPF,
+       EXECMEM_MODULE_DATA,
        EXECMEM_TYPE_MAX,
 };
Overall, it is great that kprobe/ftrace/bpf no longer depend on modules.

OTOH, I think we should merge execmem_type and existing mod_mem_type.
Otherwise, we still need to handle page permissions in multiple places.
What is our plan for that?

Thanks,
Song

quoted hunk ↗ jump to hunk
@@ -107,6 +109,23 @@ struct execmem_params *execmem_arch_params(void);
  */
 void *execmem_text_alloc(enum execmem_type type, size_t size);

+/**
+ * execmem_data_alloc - allocate memory for data coupled to code
+ * @type: type of the allocation
+ * @size: how many bytes of memory are required
+ *
+ * Allocates memory that will contain data coupled with executable code,
+ * like data sections in kernel modules.
+ *
+ * The memory will have protections defined by architecture.
+ *
+ * The allocated memory will reside in an area that does not impose
+ * restrictions on the addressing modes.
+ *
+ * Return: a pointer to the allocated memory or %NULL
+ */
+void *execmem_data_alloc(enum execmem_type type, size_t size);
+
 /**
  * execmem_free - free executable memory
  * @ptr: pointer to the memory that should be freed
diff --git a/kernel/module/main.c b/kernel/module/main.c
index c4146bfcd0a7..2ae83a6abf66 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1188,25 +1188,16 @@ void __weak module_arch_freeing_init(struct module *mod)
 {
 }

-static bool mod_mem_use_vmalloc(enum mod_mem_type type)
-{
-       return IS_ENABLED(CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC) &&
-               mod_mem_type_is_core_data(type);
-}
-
 static void *module_memory_alloc(unsigned int size, enum mod_mem_type type)
 {
-       if (mod_mem_use_vmalloc(type))
-               return vzalloc(size);
+       if (mod_mem_type_is_data(type))
+               return execmem_data_alloc(EXECMEM_MODULE_DATA, size);
        return execmem_text_alloc(EXECMEM_MODULE_TEXT, size);
 }

 static void module_memory_free(void *ptr, enum mod_mem_type type)
 {
-       if (mod_mem_use_vmalloc(type))
-               vfree(ptr);
-       else
-               execmem_free(ptr);
+       execmem_free(ptr);
 }

 static void free_mod_mem(struct module *mod)
diff --git a/mm/execmem.c b/mm/execmem.c
index abcbd07e05ac..aeff85261360 100644
--- a/mm/execmem.c
+++ b/mm/execmem.c
@@ -53,11 +53,23 @@ static void *execmem_alloc(size_t size, struct execmem_range *range)
        return kasan_reset_tag(p);
 }

+static inline bool execmem_range_is_data(enum execmem_type type)
+{
+       return type == EXECMEM_MODULE_DATA;
+}
+
 void *execmem_text_alloc(enum execmem_type type, size_t size)
 {
        return execmem_alloc(size, &execmem_params.ranges[type]);
 }

+void *execmem_data_alloc(enum execmem_type type, size_t size)
+{
+       WARN_ON_ONCE(!execmem_range_is_data(type));
+
+       return execmem_alloc(size, &execmem_params.ranges[type]);
+}
+
 void execmem_free(void *ptr)
 {
        /*
@@ -93,7 +105,10 @@ static void execmem_init_missing(struct execmem_params *p)
                struct execmem_range *r = &p->ranges[i];

                if (!r->start) {
-                       r->pgprot = default_range->pgprot;
+                       if (execmem_range_is_data(i))
+                               r->pgprot = PAGE_KERNEL;
+                       else
+                               r->pgprot = default_range->pgprot;
                        r->alignment = default_range->alignment;
                        r->start = default_range->start;
                        r->end = default_range->end;
--
2.39.2
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