Hi Vladimir,
On 2024/5/18 00:38, Vladimir 'phcoder' Serbinenko wrote:
I think that given that align is a non zero const we can trust it.
From the EROFS specific cases, they are always non-zero values,
So I agree with you on this..
Yet Daniel said ".. Be careful with underflows too." in
https://lore.kernel.org/r/zkcv7g7mjbg8s...@tomti.i.net-space.pl
although I'm not quite sure but I guess like this.
Also as a generic helper, I think `align` could be zero if it's
a variable..
Anyway, either way works for EROFS. I just try my best to do
what I could do for this first series for upstreaming and we
could move forward to the next step..
Thanks,
Gao Xiang
Le ven. 17 mai 2024, 15:56, Gao Xiang <hsiang...@linux.alibaba.com
<mailto:hsiang...@linux.alibaba.com>> a écrit :
The following EROFS patch will use this helper to handle overflow
ALIGN_UP() cases.
Signed-off-by: Gao Xiang <hsiang...@linux.alibaba.com
<mailto:hsiang...@linux.alibaba.com>>
---
include/grub/safemath.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/grub/safemath.h b/include/grub/safemath.h
index fbd9b5925..baaea0ef4 100644
--- a/include/grub/safemath.h
+++ b/include/grub/safemath.h
@@ -32,6 +32,22 @@
#define grub_cast(a, res) grub_add ((a), 0, (res))
+#define ALIGN_UP_OVF(v, align, res) \
+({ \
+ bool __failed; \
+ typeof(v) a; \
+ \
+ __failed = grub_sub ((typeof(v))(align), 1, &a); \
+ if (__failed == false) \
+ { \
+ __failed = grub_add (v, a, res); \
+ if (__failed == false) \
+ { \
+ *(res) &= ~a; \
+ } \
+ } \
+__failed;})
+
#else
#error gcc 5.1 or newer or clang 8.0 or newer is required
#endif
--
2.39.3
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