drivers/firmware/google/memconsole-coreboot.c:52:14: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour

drivers/firmware/google/memconsole-coreboot.c:52:14: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 4424 bytes --]

CC: kbuild-all(a)lists.01.org
CC: linux-kernel(a)vger.kernel.org
TO: Helge Deller <deller@gmx.de>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   dcc0b49040c70ad827a7f3d58a21b01fdb14e749
commit: 024f5b597564acced9e69305f7a9ef1202186a61 parisc: Add qemu fw_cfg interface
date:   4 months ago
:::::: branch date: 13 hours ago
:::::: commit date: 4 months ago
compiler: hppa-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

>> drivers/firmware/google/memconsole-coreboot.c:52:14: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
    if (flags & OVERFLOW) {
                ^

vim +52 drivers/firmware/google/memconsole-coreboot.c

d384d6f43d1ec3 Thierry Escande 2017-03-28  32  
a5061d028594a3 Julius Werner   2017-05-02  33  /*
a5061d028594a3 Julius Werner   2017-05-02  34   * The cbmem_console structure is read again on every access because it may
a5061d028594a3 Julius Werner   2017-05-02  35   * change at any time if runtime firmware logs new messages. This may rarely
a5061d028594a3 Julius Werner   2017-05-02  36   * lead to race conditions where the firmware overwrites the beginning of the
a5061d028594a3 Julius Werner   2017-05-02  37   * ring buffer with more lines after we have already read |cursor|. It should be
a5061d028594a3 Julius Werner   2017-05-02  38   * rare and harmless enough that we don't spend extra effort working around it.
a5061d028594a3 Julius Werner   2017-05-02  39   */
7918cfc46cfad7 Julius Werner   2017-05-02  40  static ssize_t memconsole_coreboot_read(char *buf, loff_t pos, size_t count)
7918cfc46cfad7 Julius Werner   2017-05-02  41  {
a5061d028594a3 Julius Werner   2017-05-02  42  	u32 cursor = cbmem_console->cursor & CURSOR_MASK;
a5061d028594a3 Julius Werner   2017-05-02  43  	u32 flags = cbmem_console->cursor & ~CURSOR_MASK;
40fbb23881291b Julius Werner   2017-05-23  44  	u32 size = cbmem_console_size;
a5061d028594a3 Julius Werner   2017-05-02  45  	struct seg {	/* describes ring buffer segments in logical order */
a5061d028594a3 Julius Werner   2017-05-02  46  		u32 phys;	/* physical offset from start of mem buffer */
a5061d028594a3 Julius Werner   2017-05-02  47  		u32 len;	/* length of segment */
a5061d028594a3 Julius Werner   2017-05-02  48  	} seg[2] = { {0}, {0} };
a5061d028594a3 Julius Werner   2017-05-02  49  	size_t done = 0;
a5061d028594a3 Julius Werner   2017-05-02  50  	int i;
a5061d028594a3 Julius Werner   2017-05-02  51  
a5061d028594a3 Julius Werner   2017-05-02 @52  	if (flags & OVERFLOW) {
a5061d028594a3 Julius Werner   2017-05-02  53  		if (cursor > size)	/* Shouldn't really happen, but... */
a5061d028594a3 Julius Werner   2017-05-02  54  			cursor = 0;
a5061d028594a3 Julius Werner   2017-05-02  55  		seg[0] = (struct seg){.phys = cursor, .len = size - cursor};
a5061d028594a3 Julius Werner   2017-05-02  56  		seg[1] = (struct seg){.phys = 0, .len = cursor};
a5061d028594a3 Julius Werner   2017-05-02  57  	} else {
a5061d028594a3 Julius Werner   2017-05-02  58  		seg[0] = (struct seg){.phys = 0, .len = min(cursor, size)};
a5061d028594a3 Julius Werner   2017-05-02  59  	}
a5061d028594a3 Julius Werner   2017-05-02  60  
a5061d028594a3 Julius Werner   2017-05-02  61  	for (i = 0; i < ARRAY_SIZE(seg) && count > done; i++) {
a5061d028594a3 Julius Werner   2017-05-02  62  		done += memory_read_from_buffer(buf + done, count - done, &pos,
a5061d028594a3 Julius Werner   2017-05-02  63  			cbmem_console->body + seg[i].phys, seg[i].len);
a5061d028594a3 Julius Werner   2017-05-02  64  		pos -= seg[i].len;
a5061d028594a3 Julius Werner   2017-05-02  65  	}
a5061d028594a3 Julius Werner   2017-05-02  66  	return done;
7918cfc46cfad7 Julius Werner   2017-05-02  67  }
7918cfc46cfad7 Julius Werner   2017-05-02  68  

:::::: The code at line 52 was first introduced by commit
:::::: a5061d028594a31dbf70f4554e0b7d83e5ce770f firmware: google: memconsole: Adapt to new coreboot ring buffer format

:::::: TO: Julius Werner <jwerner@chromium.org>
:::::: CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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