Ananth N Mavinakayanahalli <ana...@linux.ibm.com> writes:
> We currently just percolate the return value from analyze_instr()
> to the caller of emulate_step(), especially if it is a -1.
>
> For one particular case (opcode = 4) for instructions that
> aren't currently emulated, we are returning 'should not be
> single-stepped' while we should have returned 0 which says
> 'did not emulate, may have to single-step'.
>
> Signed-off-by: Ananth N Mavinakayanahalli <ana...@linux.ibm.com>
> Tested-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> arch/powerpc/lib/sstep.c | 49
> +++++++++++++++++++++++++---------------------
> 1 file changed, 27 insertions(+), 22 deletions(-)
>
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 5a425a4a1d88..a3a0373843cd 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -1445,34 +1445,39 @@ int analyse_instr(struct instruction_op *op, const
> struct pt_regs *regs,
>
> #ifdef __powerpc64__
> case 4:
> - if (!cpu_has_feature(CPU_FTR_ARCH_300))
> - return -1;
> -
> - switch (word & 0x3f) {
> - case 48: /* maddhd */
> - asm volatile(PPC_MADDHD(%0, %1, %2, %3) :
> - "=r" (op->val) : "r" (regs->gpr[ra]),
> - "r" (regs->gpr[rb]), "r" (regs->gpr[rc]));
> - goto compute_done;
> + /*
> + * There are very many instructions with this primary opcode
> + * introduced in the ISA as early as v2.03. However, the ones
> + * we currently emulate were all introduced with ISA 3.0
> + */
> + if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> + switch (word & 0x3f) {
> + case 48: /* maddhd */
> + asm volatile(PPC_MADDHD(%0, %1, %2, %3) :
> + "=r" (op->val) : "r"
> (regs->gpr[ra]),
> + "r" (regs->gpr[rb]), "r"
> (regs->gpr[rc]));
> + goto compute_done;
Indenting everything makes this patch harder to read, and I think makes
the resulting code harder to read too. We already have two levels of
switch here, and we're inside a ~1700 line function, so keeping things
simple is important I think.
Doesn't this achieve the same result?
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index bf7a7d62ae8b..d631baaf1da2 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -1443,8 +1443,10 @@ int analyse_instr(struct instruction_op *op, const
struct pt_regs *regs,
#ifdef __powerpc64__
case 4:
- if (!cpu_has_feature(CPU_FTR_ARCH_300))
- return -1;
+ if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
+ op->type = UNKNOWN;
+ return 0;
+ }
switch (word & 0x3f) {
case 48: /* maddhd */
@@ -1470,7 +1472,8 @@ int analyse_instr(struct instruction_op *op, const struct
pt_regs *regs,
* There are other instructions from ISA 3.0 with the same
* primary opcode which do not have emulation support yet.
*/
- return -1;
+ op->type = UNKNOWN;
+ return 0;
#endif
case 7: /* mulli */
cheers
