On Wed, Sep 06, 2017 at 04:21:50PM +0000, Okamoto, Takayuki wrote: > Hi Dave, > > I am an engineer of the postK computer from Fujitsu. > > When I tried to read "max_vl" by ptrace with this patch on our local SVE > simulator, it was read as zero. > I think the cause of this incident is that "max_vl" is set as "header->vl" > only on warning case in sve_init_header_from_task(). > "max_vl" should be set up also on normal case, like the following patch. > > > --- a/arch/arm64/kernel/ptrace.c > +++ b/arch/arm64/kernel/ptrace.c > @@ -755,6 +755,8 @@ static void sve_init_header_from_task(struct user_sve_header *header, > > if (WARN_ON(!sve_vl_valid(sve_max_vl))) > header->max_vl = header->vl; > + else > + header->max_vl = sve_max_vl; > > header->size = SVE_PT_SIZE(vq, header->flags); > header->max_size = SVE_PT_SIZE(sve_vq_from_vl(header->max_vl), Hi, thanks for reporting this. It looks like a refactoring mistake I made while removing BUG_ON()s, which I missed in my testing. Your fix looks correct and seems to work. For stylistic reasons, I may write it like this instead, but the effect should be the same: header->max_vl = sve_max_vl; if (WARN_ON(!sve_vl_valid(sve_max_vl)) header->max_vl = header->vl; Cheers ---Dave > > > Best regards, > Takayuki Okamoto > > -----Original Message----- > From: gdb-owner@xxxxxxxxxxxxxx [mailto:gdb-owner@xxxxxxxxxxxxxx] On Behalf Of Dave Martin > Sent: Friday, September 1, 2017 2:01 AM > To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>; Will Deacon <will.deacon@xxxxxxx>; Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>; Alex Bennée <alex.bennee@xxxxxxxxxx>; Szabolcs Nagy <szabolcs.nagy@xxxxxxx>; Richard Sandiford <richard.sandiford@xxxxxxx>; kvmarm@xxxxxxxxxxxxxxxxxxxxx; libc-alpha@xxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; gdb@xxxxxxxxxxxxxx; Alan Hayward <alan.hayward@xxxxxxx>; Yao Qi <Yao.Qi@xxxxxxx>; Oleg Nesterov <oleg@xxxxxxxxxx>; Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Subject: [PATCH v2 19/28] arm64/sve: ptrace and ELF coredump support > [...] > @@ -702,6 +737,210 @@ static int system_call_set(struct task_struct *target, > return ret; > } > > +#ifdef CONFIG_ARM64_SVE > + > +static void sve_init_header_from_task(struct user_sve_header *header, > + struct task_struct *target) > +{ > + unsigned int vq; > + > + memset(header, 0, sizeof(*header)); > + > + header->flags = test_tsk_thread_flag(target, TIF_SVE) ? > + SVE_PT_REGS_SVE : SVE_PT_REGS_FPSIMD; > + if (test_tsk_thread_flag(target, TIF_SVE_VL_INHERIT)) > + header->flags |= SVE_PT_VL_INHERIT; > + > + header->vl = target->thread.sve_vl; > + vq = sve_vq_from_vl(header->vl); > + > + if (WARN_ON(!sve_vl_valid(sve_max_vl))) > + header->max_vl = header->vl; > + > + header->size = SVE_PT_SIZE(vq, header->flags); > + header->max_size = SVE_PT_SIZE(sve_vq_from_vl(header->max_vl), > + SVE_PT_REGS_SVE); > +} [...]
