To fix build errors:
kernel/built-in.o: In function `bpf_trace_printk':
bpf_trace.c:(.text+0x11a254): undefined reference to `strncpy_from_unsafe'
kernel/built-in.o: In function `fetch_memory_string':
trace_kprobe.c:(.text+0x11acf8): undefined reference to `strncpy_from_unsafe'
move strncpy_from_unsafe() next to probe_kernel_read/write()
which use the same memory access style.
Reported-by: Fengguang Wu <[email protected]>
Reported-by: Guenter Roeck <[email protected]>
Fixes: 1a6877b9c0c2 ("lib: introduce strncpy_from_unsafe()")
Signed-off-by: Alexei Starovoitov <[email protected]>
---
For configs without kprobes and bpf the cost of this unused function is
~200 bytes which I think is a better trade off vs creating
new Kconfig selector just for this single function.
Another alternative is to move it to kernel/trace/trace_kprobe.c,
but then it will lose generality and probably should be removed
from include/linux/uaccess.h, so mm/maccess.c looks the best.
lib/strncpy_from_user.c | 41 -----------------------------------------
mm/maccess.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+), 41 deletions(-)
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index ead8c4a068d1..e0af6ff73d14 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -112,44 +112,3 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
return -EFAULT;
}
EXPORT_SYMBOL(strncpy_from_user);
-
-/**
- * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
- * @dst: Destination address, in kernel space. This buffer must be at
- * least @count bytes long.
- * @src: Unsafe address.
- * @count: Maximum number of bytes to copy, including the trailing NUL.
- *
- * Copies a NUL-terminated string from unsafe address to kernel buffer.
- *
- * On success, returns the length of the string INCLUDING the trailing NUL.
- *
- * If access fails, returns -EFAULT (some data may have been copied
- * and the trailing NUL added).
- *
- * If @count is smaller than the length of the string, copies @count-1 bytes,
- * sets the last byte of @dst buffer to NUL and returns @count.
- */
-long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
-{
- mm_segment_t old_fs = get_fs();
- const void *src = unsafe_addr;
- long ret;
-
- if (unlikely(count <= 0))
- return 0;
-
- set_fs(KERNEL_DS);
- pagefault_disable();
-
- do {
- ret = __copy_from_user_inatomic(dst++,
- (const void __user __force *)src++, 1);
- } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
-
- dst[-1] = '\0';
- pagefault_enable();
- set_fs(old_fs);
-
- return ret < 0 ? ret : src - unsafe_addr;
-}
diff --git a/mm/maccess.c b/mm/maccess.c
index d53adf9ba84b..34fe24759ed1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -60,3 +60,44 @@ long __probe_kernel_write(void *dst, const void *src, size_t size)
return ret ? -EFAULT : 0;
}
EXPORT_SYMBOL_GPL(probe_kernel_write);
+
+/**
+ * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
+ * @dst: Destination address, in kernel space. This buffer must be at
+ * least @count bytes long.
+ * @src: Unsafe address.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from unsafe address to kernel buffer.
+ *
+ * On success, returns the length of the string INCLUDING the trailing NUL.
+ *
+ * If access fails, returns -EFAULT (some data may have been copied
+ * and the trailing NUL added).
+ *
+ * If @count is smaller than the length of the string, copies @count-1 bytes,
+ * sets the last byte of @dst buffer to NUL and returns @count.
+ */
+long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
+{
+ mm_segment_t old_fs = get_fs();
+ const void *src = unsafe_addr;
+ long ret;
+
+ if (unlikely(count <= 0))
+ return 0;
+
+ set_fs(KERNEL_DS);
+ pagefault_disable();
+
+ do {
+ ret = __copy_from_user_inatomic(dst++,
+ (const void __user __force *)src++, 1);
+ } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
+
+ dst[-1] = '\0';
+ pagefault_enable();
+ set_fs(old_fs);
+
+ return ret < 0 ? ret : src - unsafe_addr;
+}
--
1.7.9.5
From: Alexei Starovoitov <[email protected]>
Date: Mon, 31 Aug 2015 08:57:10 -0700
> To fix build errors:
> kernel/built-in.o: In function `bpf_trace_printk':
> bpf_trace.c:(.text+0x11a254): undefined reference to `strncpy_from_unsafe'
> kernel/built-in.o: In function `fetch_memory_string':
> trace_kprobe.c:(.text+0x11acf8): undefined reference to `strncpy_from_unsafe'
>
> move strncpy_from_unsafe() next to probe_kernel_read/write()
> which use the same memory access style.
>
> Reported-by: Fengguang Wu <[email protected]>
> Reported-by: Guenter Roeck <[email protected]>
> Fixes: 1a6877b9c0c2 ("lib: introduce strncpy_from_unsafe()")
> Signed-off-by: Alexei Starovoitov <[email protected]>
> ---
> For configs without kprobes and bpf the cost of this unused function is
> ~200 bytes which I think is a better trade off vs creating
> new Kconfig selector just for this single function.
> Another alternative is to move it to kernel/trace/trace_kprobe.c,
> but then it will lose generality and probably should be removed
> from include/linux/uaccess.h, so mm/maccess.c looks the best.
Ok, applied.
On 08/31/2015 12:36 PM, David Miller wrote:
> From: Alexei Starovoitov <[email protected]>
> Date: Mon, 31 Aug 2015 08:57:10 -0700
>
>> To fix build errors:
>> kernel/built-in.o: In function `bpf_trace_printk':
>> bpf_trace.c:(.text+0x11a254): undefined reference to `strncpy_from_unsafe'
>> kernel/built-in.o: In function `fetch_memory_string':
>> trace_kprobe.c:(.text+0x11acf8): undefined reference to `strncpy_from_unsafe'
>>
>> move strncpy_from_unsafe() next to probe_kernel_read/write()
>> which use the same memory access style.
>>
>> Reported-by: Fengguang Wu <[email protected]>
>> Reported-by: Guenter Roeck <[email protected]>
Too late, but:
Tested-by: Guenter Roeck <[email protected]>
Guenter
>> Fixes: 1a6877b9c0c2 ("lib: introduce strncpy_from_unsafe()")
>> Signed-off-by: Alexei Starovoitov <[email protected]>
>> ---
>> For configs without kprobes and bpf the cost of this unused function is
>> ~200 bytes which I think is a better trade off vs creating
>> new Kconfig selector just for this single function.
>> Another alternative is to move it to kernel/trace/trace_kprobe.c,
>> but then it will lose generality and probably should be removed
>> from include/linux/uaccess.h, so mm/maccess.c looks the best.
>
> Ok, applied.
>