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Donenfeld" To: Christophe Leroy Cc: Andrew Morton , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Nicholas Piggin , Naveen N Rao , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Shuah Khan , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, llvm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, Adhemerval Zanella , Xi Ruoyao Subject: Re: [PATCH v5 4/5] powerpc/vdso: Wire up getrandom() vDSO implementation on VDSO32 Message-ID: References: <1f49c2ce009f8b007ab0676fb41187b2d54f28b2.1725304404.git.christophe.leroy@csgroup.eu> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Thu, Sep 05, 2024 at 06:13:29PM +0200, Jason A. Donenfeld wrote: > > +/* > > + * The macro sets two stack frames, one for the caller and one for the callee > > + * because there are no requirement for the caller to set a stack frame when > > + * calling VDSO so it may have omitted to set one, especially on PPC64 > > + */ > > + > > +.macro cvdso_call funct > > + .cfi_startproc > > + PPC_STLU r1, -PPC_MIN_STKFRM(r1) > > + .cfi_adjust_cfa_offset PPC_MIN_STKFRM > > + mflr r0 > > + PPC_STLU r1, -PPC_MIN_STKFRM(r1) > > + .cfi_adjust_cfa_offset PPC_MIN_STKFRM > > + PPC_STL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1) > > + .cfi_rel_offset lr, PPC_MIN_STKFRM + PPC_LR_STKOFF > > + get_datapage r8 > > + addi r8, r8, VDSO_RNG_DATA_OFFSET > > + bl CFUNC(DOTSYM(\funct)) > > + PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1) > > + cmpwi r3, 0 > > + mtlr r0 > > + addi r1, r1, 2 * PPC_MIN_STKFRM > > + .cfi_restore lr > > + .cfi_def_cfa_offset 0 > > + crclr so > > + bgelr+ > > + crset so > > + neg r3, r3 > > + blr > > + .cfi_endproc > > +.endm > > You wrote in an earlier email that this worked with time namespaces, but > in my testing that doesn't seem to be the case. > > From my test harness [1]: > > Normal single thread > vdso: 25000000 times in 12.494133131 seconds > libc: 25000000 times in 69.594625188 seconds > syscall: 25000000 times in 67.349243972 seconds > Time namespace single thread > vdso: 25000000 times in 71.673057436 seconds > libc: 25000000 times in 71.712774121 seconds > syscall: 25000000 times in 66.902318080 seconds > > I'm seeing this on ppc, ppc64, and ppc64le. > > Can you figure out what's going on and send a fix, which I'll squash > into this commit? Also, FYI, I've verified that things do work on x86_64, loongarch64, arm64, and arm64_be. It's just the ppc archs that are broken. So this test _is_ a good one.