From: Benjamin Gray <bgray@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Benjamin Gray <bgray@linux.ibm.com>
Subject: [PATCH 02/12] powerpc/pseries: Restructure hvc_get_chars() endianness
Date: Wed, 11 Oct 2023 16:37:01 +1100 [thread overview]
Message-ID: <20231011053711.93427-3-bgray@linux.ibm.com> (raw)
In-Reply-To: <20231011053711.93427-1-bgray@linux.ibm.com>
Sparse reports an endian mismatch in hvc_get_chars().
At first it seemed like the retbuf should be __be64[], but actually
retbuf holds serialized registers returned by the hypervisor call, so
it's correctly CPU endian typed.
Instead, it is the be64_to_cpu() that's misleading. The intent is to do
a byte swap on a little endian CPU. The swap is required because we
wanted to store the register values to memory without 'swapping' bytes,
so that the high order byte of the first register is the first byte
in the result buffer.
In diagram form, on a LE CPU with the letters representing the return
string bytes:
(register bytes) A B C D E F G H I J K L M N O P
(retbuf mem bytes) H G F E D C B A P O N M L K J I
(buf/lbuf mem bytes) A B C D E F G H I J K L M N O P
So retbuf stores the registers in CPU endian, and buf always stores in
big endian.
So replace the byte swap function with cpu_to_be64() and cast lbuf as an
array of __be64 to match the semantics closer.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
arch/powerpc/platforms/pseries/hvconsole.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/hvconsole.c b/arch/powerpc/platforms/pseries/hvconsole.c
index 1ac52963e08b..647718a15e78 100644
--- a/arch/powerpc/platforms/pseries/hvconsole.c
+++ b/arch/powerpc/platforms/pseries/hvconsole.c
@@ -29,11 +29,11 @@ int hvc_get_chars(uint32_t vtermno, char *buf, int count)
{
long ret;
unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
- unsigned long *lbuf = (unsigned long *)buf;
+ __be64 *lbuf = (__be64 __force *)buf;
ret = plpar_hcall(H_GET_TERM_CHAR, retbuf, vtermno);
- lbuf[0] = be64_to_cpu(retbuf[1]);
- lbuf[1] = be64_to_cpu(retbuf[2]);
+ lbuf[0] = cpu_to_be64(retbuf[1]);
+ lbuf[1] = cpu_to_be64(retbuf[2]);
if (ret == H_SUCCESS)
return retbuf[0];
--
2.39.2
next prev parent reply other threads:[~2023-10-11 5:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-11 5:36 [PATCH 00/12] Miscellaneous Sparse fixes Benjamin Gray
2023-10-11 5:37 ` [PATCH 01/12] powerpc/xive: Fix endian conversion size Benjamin Gray
2023-10-11 5:37 ` Benjamin Gray [this message]
2023-10-30 13:16 ` [PATCH 02/12] powerpc/pseries: Restructure hvc_get_chars() endianness Aneesh Kumar K.V
2024-02-20 7:10 ` Christophe Leroy
2023-10-11 5:37 ` [PATCH 03/12] powerpc: Explicitly reverse bytes when checking for byte reversal Benjamin Gray
2023-10-11 5:37 ` [PATCH 04/12] powerpc: Use NULL instead of 0 for null pointers Benjamin Gray
2023-10-11 5:37 ` [PATCH 05/12] powerpc: Remove extern from function implementations Benjamin Gray
2023-10-11 5:37 ` [PATCH 06/12] powerpc: Annotate endianness of various variables and functions Benjamin Gray
2023-10-11 5:37 ` [PATCH 07/12] powerpc/kvm: Force cast endianness of KVM shared regs Benjamin Gray
2023-10-11 5:37 ` [PATCH 08/12] powerpc/opal: Annotate out param endianness Benjamin Gray
2023-10-11 5:37 ` [PATCH 09/12] powerpc/uaccess: Cast away __user annotation after verification Benjamin Gray
2023-10-11 5:37 ` [PATCH 10/12] powerpc: Cast away __iomem in low level IO routines Benjamin Gray
2023-10-11 5:37 ` [PATCH 11/12] powerpc/eeh: Remove unnecessary cast Benjamin Gray
2023-10-11 5:37 ` [PATCH 12/12] powerpc/fadump: Annotate endianness cast with __force Benjamin Gray
2023-10-27 9:59 ` (subset) [PATCH 00/12] Miscellaneous Sparse fixes Michael Ellerman
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