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  1. Mar 26, 2013
  3. Mar 14, 2013
  5. Mar 08, 2013
    • Ivan Djelic's avatar
      ARM: 7668/1: fix memset-related crashes caused by recent GCC (4.7.2) optimizations · 455bd4c4
      Ivan Djelic authored 
      

Recent GCC versions (e.g. GCC-4.7.2) perform optimizations based on
assumptions about the implementation of memset and similar functions.
The current ARM optimized memset code does not return the value of
its first argument, as is usually expected from standard implementations.

For instance in the following function:

void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
{
	memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
	waiter->magic = waiter;
	INIT_LIST_HEAD(&waiter->list);
}

compiled as:

800554d0 <debug_mutex_lock_common>:
800554d0:       e92d4008        push    {r3, lr}
800554d4:       e1a00001        mov     r0, r1
800554d8:       e3a02010        mov     r2, #16 ; 0x10
800554dc:       e3a01011        mov     r1, #17 ; 0x11
800554e0:       eb04426e        bl      80165ea0 <memset>
800554e4:       e1a03000        mov     r3, r0
800554e8:       e583000c        str     r0, [r3, #12]
800554ec:       e5830000        str     r0, [r3]
800554f0:       e5830004        str     r0, [r3, #4]
800554f4:       e8bd8008        pop     {r3, pc}

GCC assumes memset returns the value of pointer 'waiter' in register r0; causing
register/memory corruptions.

This patch fixes the return value of the assembly version of memset.
It adds a 'mov' instruction and merges an additional load+store into
existing load/store instructions.
For ease of review, here is a breakdown of the patch into 4 simple steps:

Step 1
======
Perform the following substitutions:
ip -> r8, then
r0 -> ip,
and insert 'mov ip, r0' as the first statement of the function.
At this point, we have a memset() implementation returning the proper result,
but corrupting r8 on some paths (the ones that were using ip).

Step 2
======
Make sure r8 is saved and restored when (! CALGN(1)+0) == 1:

save r8:
-       str     lr, [sp, #-4]!
+       stmfd   sp!, {r8, lr}

and restore r8 on both exit paths:
-       ldmeqfd sp!, {pc}               @ Now <64 bytes to go.
+       ldmeqfd sp!, {r8, pc}           @ Now <64 bytes to go.
(...)
        tst     r2, #16
        stmneia ip!, {r1, r3, r8, lr}
-       ldr     lr, [sp], #4
+       ldmfd   sp!, {r8, lr}

Step 3
======
Make sure r8 is saved and restored when (! CALGN(1)+0) == 0:

save r8:
-       stmfd   sp!, {r4-r7, lr}
+       stmfd   sp!, {r4-r8, lr}

and restore r8 on both exit paths:
        bgt     3b
-       ldmeqfd sp!, {r4-r7, pc}
+       ldmeqfd sp!, {r4-r8, pc}
(...)
        tst     r2, #16
        stmneia ip!, {r4-r7}
-       ldmfd   sp!, {r4-r7, lr}
+       ldmfd   sp!, {r4-r8, lr}

Step 4
======
Rewrite register list "r4-r7, r8" as "r4-r8".

Signed-off-by: default avatarIvan Djelic <ivan.djelic@parrot.com>
Reviewed-by: default avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: default avatarDirk Behme <dirk.behme@gmail.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      455bd4c4
  7. Mar 07, 2013
    • Stephen Boyd's avatar
      ARM: 7667/1: perf: Fix section mismatch on armpmu_init() · 44d6b1fc
      Stephen Boyd authored 
      

WARNING: vmlinux.o(.text+0xfb80): Section mismatch in reference
from the function armpmu_register() to the function
.init.text:armpmu_init()
The function armpmu_register() references
the function __init armpmu_init().
This is often because armpmu_register lacks a __init
annotation or the annotation of armpmu_init is wrong.

Just drop the __init marking on armpmu_init() because
armpmu_register() no longer has an __init marking.

Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      44d6b1fc
    • Jonathan Austin's avatar
      ARM: 7666/1: decompressor: add -mno-single-pic-base for building the decompressor · b8083f86
      Jonathan Austin authored 
      

Before jumping to (position independent) C-code from the decompressor's
assembler world we set-up the C environment. This setup currently does not
set r9, which for arm-none-uclinux-uclibceabi toolchains is by default
expected to be the PIC offset base register (IE should point to the
beginning of the GOT).

Currently, therefore, in order to build working kernels that use the
decompressor it is necessary to use an arm-linux-gnueabi toolchain, or
similar. uClinux toolchains cause a prefetch abort to occur at the beginning
of the decompress_kernel function.

This patch allows uClinux toolchains to build bootable zImages by forcing
the -mno-single-pic-base option, which ensures that the location of the GOT
is re-derived each time it is required, and r9 becomes free for use as a
general purpose register.

This has a small (4% in instruction terms) advantage over the alternative of
setting r9 to point to the GOT before calling into the C-world.

Signed-off-by: default avatarJonathan Austin <jonathan.austin@arm.com>
Acked-by: default avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      b8083f86
  9. Mar 04, 2013
  11. Mar 02, 2013
    • Russell King's avatar
      ARM: Fix broken commit 0cc41e4a corrupting kernel messages · ded3ef0f
      Russell King authored 
      Commit 0cc41e4a

 (arch: remove direct definitions of KERN_<LEVEL>
uses) is broken - not enough thought was put into changing:

	.asciz	"string"

to

	.asciz	"string1" "string2"

The problem is that each string gets _separately_ NUL terminated, so
the result is a string containing:

	"string1\0string2\0"

rather than:

	"string1string2\0"

With our new printk levels, this ends up as - eg, KERN_DEBUG "string":

	0x01 0x00 0x07 0x00 "string" 0x00

which produces lots of \x01 in the kernel log.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      ded3ef0f
  13. Mar 01, 2013