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MIPS: BPF: Fix load delay slots.

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The entire bpf_jit_asm.S is written in noreorder mode because "we know
better" according to a comment.  This also prevented the assembler from
throwing in the required NOPs for MIPS I processors which have no
load-use interlock, thus the load's consumer might end up using the
old value of the register from prior to the load.

Fixed by putting the assembler in reorder mode for just the affected
load instructions.  This is not enough for gas to actually try to be
clever by looking at the next instruction and inserting a nop only
when needed but as the comment said "we know better", so getting gas
to unconditionally emit a NOP is just right in this case and prevents
adding further ifdefery.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle 2015-10-02 09:48:57 +02:00
parent 1e16a8f116
commit 0c5d187828
1 changed files with 4 additions and 0 deletions
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4
arch/mips/net/bpf_jit_asm.S
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@ -61,7 +61,9 @@ FEXPORT(sk_load_word_positive)
is_offset_in_header(4, word)
/* Offset within header boundaries */
PTR_ADDU t1, $r_skb_data, offset
.set reorder
lw $r_A, 0(t1)
.set noreorder
#ifdef CONFIG_CPU_LITTLE_ENDIAN
# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
wsbh t0, $r_A
@ -88,7 +90,9 @@ FEXPORT(sk_load_half_positive)
is_offset_in_header(2, half)
/* Offset within header boundaries */
PTR_ADDU t1, $r_skb_data, offset
.set reorder
lh $r_A, 0(t1)
.set noreorder
#ifdef CONFIG_CPU_LITTLE_ENDIAN
# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
wsbh t0, $r_A