From: Linus Torvalds Date: Tue, 17 Mar 2009 17:02:35 +0000 (-0700) Subject: Avoid 64-bit "switch()" statements on 32-bit architectures X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=ee568b25ee9e160b32d1aef73d8b2ee9c05d34db;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git Avoid 64-bit "switch()" statements on 32-bit architectures Commit ee6f779b9e0851e2f7da292a9f58e0095edf615a ("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 Cc: Zhang Le Signed-off-by: Linus Torvalds --- diff --git a/fs/proc/base.c b/fs/proc/base.c index cc6ea2329e71..beaa0ce3b82e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -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)