[PATCH] mips: increase stack alignment in clone to match the ABI
Xi Ruoyao
xry111@mengyan1223.wang
Fri Aug 13 10:43:20 GMT 2021
Hi Joseph,
Sorry for this, but I have to admit I've made an error in the previous
patch. In MIPS documentations one "word" is defined 32-bit (4-byte), so
a "doubleword" is 8-byte and a "quadword" is 16-byte. I misinterpreted
"doubleword" as a "dword" we normally uses for 4-byte, so the alignment
is actually insufficient.
I'm not sure why "tst-misaligned-stack" passed with the previous
problematic patch on my board. Maybe it was pure luck, or my CPU used
to test the patch supports some non-standard unaligned access.
The following patch should fix this:
In "mips: align stack in clone [BZ #28223]"
(commit 1f51cd9a860ee45eee8a56fb2ba925267a2a7bfe) I made a mistake: I
misbelieved one "word" was 2-byte and "doubleword" should be 4-byte.
But in MIPS ABI one "word" is defined 32-bit (4-byte), so "doubleword" is
8-byte [1], and "quadword" is 16-byte [2].
[1]: "System V Application Binary Interface: MIPS(R) RISC Processor
Supplement, 3rd edition", page 3-31
[2]: "MIPSpro(TM) 64-Bit Porting and Transition Guide", page 23
---
sysdeps/unix/sysv/linux/mips/clone.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/mips/clone.S b/sysdeps/unix/sysv/linux/mips/clone.S
index 43a5ad3a40..81d814ba4d 100644
--- a/sysdeps/unix/sysv/linux/mips/clone.S
+++ b/sysdeps/unix/sysv/linux/mips/clone.S
@@ -57,9 +57,9 @@ NESTED(__clone,4*SZREG,sp)
/* Align stack to 4/8 bytes per the ABI. */
#if _MIPS_SIM == _ABIO32
- li t0,-4
-#else
li t0,-8
+#else
+ li t0,-16
#endif
and a1,a1,t0
--
2.32.0
Sorry again for the error.
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