MIPS: DEC/SNI: O32 wrapper stack switching fixes

Commit 231a35d37293ab88d325a9cb94e5474c156282c0 [[MIPS] RM: Collected
changes] broke DECstation support by introducing an incompatible copy of
arch/mips/dec/prom/call_o32.S in arch/mips/fw/lib/, built unconditionally.
The copy happens to land earlier of the two among the modules used in the
link and is therefore chosen for the DECstation rather than the intended
original.  As a result random kernel data is corrupted because a pointer
to the "%s" formatted output template is used as a temporary stack pointer
rather than being passed down to prom_printf.  This also explains why
prom_printf still works, up to a point -- the next argument is the actual
string to output so it works just fine as the output template until enough
kernel data has been corrupted to cause a crash.

This change adjusts the modified wrapper in arch/mips/fw/lib/call_o32.S to
let callers request no stack switching by passing a null temporary stack
pointer in $a1, reworks the DECstation callers to work with the updated
interface and removes the old copy from arch/mips/dec/prom/call_o32.S.  A
few minor readability adjustments are included as well, most importantly
O32_SZREG is now used throughout where applicable rather than hardcoded
multiplies of 4 and $fp is used to access the argument save area as a more
usual register to operate the stack with rather than $s0.

Finally an update is made to the temporary stack space used by the SNI
platform to guarantee 8-byte alignment as per o32 requirements.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6668/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 0 insertions, 90 deletions

diff --git a/arch/mips/dec/prom/Makefile b/arch/mips/dec/prom/Makefile
index 064ae7a76bdc..ae73e42ac20b 100644
--- a/arch/mips/dec/prom/Makefile
+++ b/arch/mips/dec/prom/Makefile
@@ -6,4 +6,3 @@
 lib-y			+= init.o memory.o cmdline.o identify.o console.o
 
 lib-$(CONFIG_32BIT)	+= locore.o
-lib-$(CONFIG_64BIT)	+= call_o32.o
diff --git a/arch/mips/dec/prom/call_o32.S b/arch/mips/dec/prom/call_o32.S
deleted file mode 100644
index 8c8498159e43..000000000000
--- a/arch/mips/dec/prom/call_o32.S
+++ /dev/null
@@ -1,89 +0,0 @@
-/*
- *	O32 interface for the 64 (or N32) ABI.
- *
- *	Copyright (C) 2002  Maciej W. Rozycki
- *
- *	This program is free software; you can redistribute it and/or
- *	modify it under the terms of the GNU General Public License
- *	as published by the Free Software Foundation; either version
- *	2 of the License, or (at your option) any later version.
- */
-
-#include <asm/asm.h>
-#include <asm/regdef.h>
-
-/* Maximum number of arguments supported.  Must be even!  */
-#define O32_ARGC	32
-/* Number of static registers we save.  */
-#define O32_STATC	11
-/* Frame size for both of the above.  */
-#define O32_FRAMESZ	(4 * O32_ARGC + SZREG * O32_STATC)
-
-		.text
-
-/*
- * O32 function call dispatcher, for interfacing 32-bit ROM routines.
- *
- * The standard 64 (N32) calling sequence is supported, with a0
- * holding a function pointer, a1-a7 -- its first seven arguments
- * and the stack -- remaining ones (up to O32_ARGC, including a1-a7).
- * Static registers, gp and fp are preserved, v0 holds a result.
- * This code relies on the called o32 function for sp and ra
- * restoration and thus both this dispatcher and the current stack
- * have to be placed in a KSEGx (or KUSEG) address space.  Any
- * pointers passed have to point to addresses within one of these
- * spaces as well.
- */
-NESTED(call_o32, O32_FRAMESZ, ra)
-		REG_SUBU	sp,O32_FRAMESZ
-
-		REG_S		ra,O32_FRAMESZ-1*SZREG(sp)
-		REG_S		fp,O32_FRAMESZ-2*SZREG(sp)
-		REG_S		gp,O32_FRAMESZ-3*SZREG(sp)
-		REG_S		s7,O32_FRAMESZ-4*SZREG(sp)
-		REG_S		s6,O32_FRAMESZ-5*SZREG(sp)
-		REG_S		s5,O32_FRAMESZ-6*SZREG(sp)
-		REG_S		s4,O32_FRAMESZ-7*SZREG(sp)
-		REG_S		s3,O32_FRAMESZ-8*SZREG(sp)
-		REG_S		s2,O32_FRAMESZ-9*SZREG(sp)
-		REG_S		s1,O32_FRAMESZ-10*SZREG(sp)
-		REG_S		s0,O32_FRAMESZ-11*SZREG(sp)
-
-		move		jp,a0
-
-		sll		a0,a1,zero
-		sll		a1,a2,zero
-		sll		a2,a3,zero
-		sll		a3,a4,zero
-		sw		a5,0x10(sp)
-		sw		a6,0x14(sp)
-		sw		a7,0x18(sp)
-
-		PTR_LA		t0,O32_FRAMESZ(sp)
-		PTR_LA		t1,0x1c(sp)
-		li		t2,O32_ARGC-7
-1:
-		lw		t3,(t0)
-		REG_ADDU	t0,SZREG
-		sw		t3,(t1)
-		REG_SUBU	t2,1
-		REG_ADDU	t1,4
-		bnez		t2,1b
-
-		jalr		jp
-
-		REG_L		s0,O32_FRAMESZ-11*SZREG(sp)
-		REG_L		s1,O32_FRAMESZ-10*SZREG(sp)
-		REG_L		s2,O32_FRAMESZ-9*SZREG(sp)
-		REG_L		s3,O32_FRAMESZ-8*SZREG(sp)
-		REG_L		s4,O32_FRAMESZ-7*SZREG(sp)
-		REG_L		s5,O32_FRAMESZ-6*SZREG(sp)
-		REG_L		s6,O32_FRAMESZ-5*SZREG(sp)
-		REG_L		s7,O32_FRAMESZ-4*SZREG(sp)
-		REG_L		gp,O32_FRAMESZ-3*SZREG(sp)
-		REG_L		fp,O32_FRAMESZ-2*SZREG(sp)
-		REG_L		ra,O32_FRAMESZ-1*SZREG(sp)
-
-		REG_ADDU	sp,O32_FRAMESZ
-		jr		ra
-END(call_o32)