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Avoid 64-bit "switch()" statements on 32-bit architectures

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Commit ee6f779b9e ("filp->f_pos not
correctly updated in proc_task_readdir") changed the proc code to use
filp->f_pos directly, rather than through a temporary variable.  In the
process, that caused the operations to be done on the full 64 bits, even
though the offset is never that big.

That's all fine and dandy per se, but for some unfathomable reason gcc
generates absolutely horrid code when using 64-bit values in switch()
statements.  To the point of actually calling out to gcc helper
functions like __cmpdi2 rather than just doing the trivial comparisons
directly the way gcc does for normal compares.  At which point we get
link failures, because we really don't want to support that kind of
crazy code.

Fix this by just casting the f_pos value to "unsigned long", which
is plenty big enough for /proc, and avoids the gcc code generation issue.

Reported-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Zhang Le <r0bertz@gentoo.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2009-03-17 10:02:35 -07:00
parent 30390880de
commit ee568b25ee
1 changed files with 1 additions and 1 deletions
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2
fs/proc/base.c
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@ -3082,7 +3082,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
goto out_no_task;
retval = 0;
switch (filp->f_pos) {
switch ((unsigned long)filp->f_pos) {
case 0:
ino = inode->i_ino;
if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) < 0)