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x86/paravirt: Detect over-sized patching bugs in paravirt_patch_call()

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paravirt_patch_call() currently handles patching failures inconsistently:
we generate a warning in the retpoline case, but don't in other cases where
we might end up with a non-working kernel as well.

So just convert it all to a BUG_ON(), these patching calls are *not* supposed
to fail, and if they do we want to know it immediately.

This also makes the kernel smaller and removes an #ifdef ugly.

I tried it with a richly paravirt-enabled kernel and no patching bugs
were detected.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20190425095039.GC115378@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2019-04-25 11:50:39 +02:00
parent 2777cae2b1
commit 11e86dc7f2
1 changed files with 8 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/kernel/paravirt.c
View File

@@ -73,21 +73,21 @@ struct branch {
static unsigned paravirt_patch_call(void *insnbuf, const void *target,
unsigned long addr, unsigned len)
{
const int call_len = 5;
struct branch *b = insnbuf;
unsigned long delta = (unsigned long)target - (addr+5);
unsigned long delta = (unsigned long)target - (addr+call_len);
if (len < 5) {
#ifdef CONFIG_RETPOLINE
WARN_ONCE(1, "Failing to patch indirect CALL in %ps\n", (void *)addr);
#endif
return len; /* call too long for patch site */
if (len < call_len) {
pr_warn("paravirt: Failed to patch indirect CALL at %ps\n", (void *)addr);
/* Kernel might not be viable if patching fails, bail out: */
BUG_ON(1);
}
b->opcode = 0xe8; /* call */
b->delta = delta;
BUILD_BUG_ON(sizeof(*b) != 5);
BUILD_BUG_ON(sizeof(*b) != call_len);
return 5;
return call_len;
}
#ifdef CONFIG_PARAVIRT_XXL