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Fixes objtool warning on write_allowlist() via attribute "cold". #189

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Fixes objtool warning on write_allowlist() via attribute "cold". #189

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10 changes: 10 additions & 0 deletions msr_allowlist.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,8 +84,18 @@ static int open_allowlist(struct inode *inode, struct file *file)
* The first pass is to ensure that the input file is valid. If the file is
* valid, we will then delete the current white list and then perform the
* second pass to actually create the new white list.
*
* gcc v8 (ish?) introduced the "cold" attribute. Linux kernel versions
* prior to v5 (ish?) have an objtool that erroneously detects fallthroughs
* between write_allowlist() and write_allowlist.cold() (and vice versa).
* To get rid of that warning, add the "cold" attribute to the entire function
* when working with older kernels.
*/
#if defined __has_attribute && __has_attribute(cold) && LINUX_VERSION_CODE < KERNEL_VERSION(5,0,0)
__attribute__((cold)) static ssize_t write_allowlist(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
#else
static ssize_t write_allowlist(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
#endif
{
int err = 0;
const u32 __user *tmp = (const u32 __user *)buf;
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