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selftests/powerpc: Fix ptrace tm failure

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Test ptrace-tm-spd-gpr fails on current kernel (4.19) due to a segmentation
fault that happens on the child process prior to setting cptr[2] = 1. This
causes the parent process to wait forever at 'while (!pptr[2])' and the test to
be killed by the test harness framework by timeout, thus, failing.

The segmentation fault happens because of a inline assembly being
generated as:

	0x10000355c <tm_spd_gpr+492>    lfs    f0, 0(0)

This is reading memory position 0x0 and causing the segmentation fault.

This code is being generated by ASM_LOAD_FPR_SINGLE_PRECISION(flt_4), where
flt_4 is passed to the inline assembly block as:

	[flt_4] "r" (&d)

Since the inline assembly 'r' constraint means any GPR, gpr0 is being
chosen, thus causing this issue when issuing a Load Floating-Point Single
instruction.

This patch simply changes the constraint to 'b', which specify that this
register will be used as base, and r0 is not allowed to be used, avoiding
this issue.

Other than that, removing flt_2 register from the input operands, since it
is not used by the inline assembly code at all.

Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Breno Leitao 2018-10-22 18:16:26 -03:00 committed by Michael Ellerman
parent c43befca86
commit 48dc0ef190
1 changed files with 2 additions and 2 deletions
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4
tools/testing/selftests/powerpc/ptrace/ptrace-tm-spd-gpr.c
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@ -67,8 +67,8 @@ trans:
"3: ;"
: [res] "=r" (result), [texasr] "=r" (texasr)
: [gpr_1]"i"(GPR_1), [gpr_2]"i"(GPR_2), [gpr_4]"i"(GPR_4),
[sprn_texasr] "i" (SPRN_TEXASR), [flt_1] "r" (&a),
[flt_2] "r" (&b), [flt_4] "r" (&d)
[sprn_texasr] "i" (SPRN_TEXASR), [flt_1] "b" (&a),
[flt_4] "b" (&d)
: "memory", "r5", "r6", "r7",
"r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
"r16", "r17", "r18", "r19", "r20", "r21", "r22", "r23",