This is a note to let you know that I have just added a patch titled
MIPS: MSA: Fix a link error on `_init_msa_upper' with older GCC
to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree
which can be found at:
https://git.launchpad.net/~canonical-kernel/linux/+git/linux-stable-ckt/log/?h=linux-4.2.y-queue
This patch is scheduled to be released in version 4.2.8-ckt12.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
---8<------------------------------------------------------------
>From 8a49bd2301359eb122d55c99d4b17045b9dfa435 Mon Sep 17 00:00:00 2001
From: "Maciej W. Rozycki" <macro@xxxxxxxxxx>
Date: Tue, 17 May 2016 06:12:27 +0100
Subject: MIPS: MSA: Fix a link error on `_init_msa_upper' with older GCC
commit e49d38488515057dba8f0c2ba4cfde5be4a7281f upstream.
Fix a build regression from commit c9017757c532 ("MIPS: init upper 64b
of vector registers when MSA is first used"):
arch/mips/built-in.o: In function `enable_restore_fp_context':
traps.c:(.text+0xbb90): undefined reference to `_init_msa_upper'
traps.c:(.text+0xbb90): relocation truncated to fit: R_MIPS_26 against `_init_msa_upper'
traps.c:(.text+0xbef0): undefined reference to `_init_msa_upper'
traps.c:(.text+0xbef0): relocation truncated to fit: R_MIPS_26 against `_init_msa_upper'
to !CONFIG_CPU_HAS_MSA configurations with older GCC versions, which are
unable to figure out that calls to `_init_msa_upper' are indeed dead.
Of the many ways to tackle this failure choose the approach we have
already taken in `thread_msa_context_live'.
[ralf@xxxxxxxxxxxxxx: Drop patch segment to junk file.]
Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/13271/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
arch/mips/include/asm/msa.h | 13 +++++++++++++
arch/mips/kernel/traps.c | 6 +++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/mips/include/asm/msa.h b/arch/mips/include/asm/msa.h
index af5638b..38bbeda 100644
--- a/arch/mips/include/asm/msa.h
+++ b/arch/mips/include/asm/msa.h
@@ -67,6 +67,19 @@ static inline void restore_msa(struct task_struct *t)
_restore_msa(t);
}
+static inline void init_msa_upper(void)
+{
+ /*
+ * Check cpu_has_msa only if it's a constant. This will allow the
+ * compiler to optimise out code for CPUs without MSA without adding
+ * an extra redundant check for CPUs with MSA.
+ */
+ if (__builtin_constant_p(cpu_has_msa) && !cpu_has_msa)
+ return;
+
+ _init_msa_upper();
+}
+
#ifdef TOOLCHAIN_SUPPORTS_MSA
#define __BUILD_MSA_CTL_REG(name, cs) \
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 86454f5..4f1d297 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1229,7 +1229,7 @@ static int enable_restore_fp_context(int msa)
err = init_fpu();
if (msa && !err) {
enable_msa();
- _init_msa_upper();
+ init_msa_upper();
set_thread_flag(TIF_USEDMSA);
set_thread_flag(TIF_MSA_CTX_LIVE);
}
@@ -1292,7 +1292,7 @@ static int enable_restore_fp_context(int msa)
*/
prior_msa = test_and_set_thread_flag(TIF_MSA_CTX_LIVE);
if (!prior_msa && was_fpu_owner) {
- _init_msa_upper();
+ init_msa_upper();
goto out;
}
@@ -1309,7 +1309,7 @@ static int enable_restore_fp_context(int msa)
* of each vector register such that it cannot see data left
* behind by another task.
*/
- _init_msa_upper();
+ init_msa_upper();
} else {
/* We need to restore the vector context. */
restore_msa(current);
--
2.7.4
