[PATCH 3.18 26/38] MIPS: End asm function prologue macros with .insn

Greg Kroah-Hartman
2017-11-19T14:31:43Z

From: Paul Burton <paul.burton@imgtec.com>

[ Upstream commit 08889582b8aa0bbc01a1e5a0033b9f98d2e11caa ]

When building a kernel targeting a microMIPS ISA, recent GNU linkers
will fail the link if they cannot determine that the target of a branch
or jump is microMIPS code, with errors such as the following:

mips-img-linux-gnu-ld: arch/mips/built-in.o: .text+0x542c:
Unsupported jump between ISA modes; consider recompiling with
interlinking enabled.
mips-img-linux-gnu-ld: final link failed: Bad value

or:

./arch/mips/include/asm/uaccess.h:1017: warning: JALX to a
non-word-aligned address

Placing anything other than an instruction at the start of a function
written in assembly appears to trigger such errors. In order to prepare
for allowing us to follow function prologue macros with an EXPORT_SYMBOL
invocation, end the prologue macros (LEAD, NESTED & FEXPORT) with a
.insn directive. This ensures that the start of the function is marked
as code, which always makes sense for functions & safely prevents us
from hitting the link errors described above.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14508/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/mips/include/asm/asm.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/mips/include/asm/asm.h
+++ b/arch/mips/include/asm/asm.h
@@ -54,7 +54,8 @@
.align 2; \
.type symbol, @function; \
.ent symbol, 0; \
-symbol: .frame sp, 0, ra
+symbol: .frame sp, 0, ra; \
+ .insn

/*
* NESTED - declare nested routine entry point
@@ -63,8 +64,9 @@ symbol: .frame sp, 0, ra
.globl symbol; \
.align 2; \
.type symbol, @function; \
- .ent symbol, 0; \
-symbol: .frame sp, framesize, rpc
+ .ent symbol, 0; \
+symbol: .frame sp, framesize, rpc; \
+ .insn

/*
* END - mark end of function
@@ -86,7 +88,7 @@ symbol:
#define FEXPORT(symbol) \
.globl symbol; \
.type symbol, @function; \
-symbol:
+symbol: .insn

/*
* ABS - export absolute symbol