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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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B650F1C0009 X-Stat-Signature: kr4mdm1cumcjripd1xpgnqr3ar7ttphg X-Rspam-User: X-HE-Tag: 1725593074-780180 X-HE-Meta: U2FsdGVkX1+Dvu4ubj4RHVcZTr4C96XFmZPLLUBVg2H9opxKe7i07BIZ7/WeL0hAFs7HVNJJVwTfWocwVSZ1AcewQQJO98ythKXBNzLaleKi3pVfsJXpdEgXsqsZW/S+dChMRRgWlxMWD6RC3Ku13Be3prBzs45Re2xdYkDI+qMtT2Mt8PHlQqx8Cryn0pVEsUSaw4WV5E+AZ/2N5k1HOwzIZRNboNv3srL2+BZs/kY6CHJhcYd+IGGfJO0x+T4zFmw4HsLuyqA389dSNYIg0oMX5yqpAo0YzVPpwO3CM6bizX82whErMpUsj6TgpE5dOnZUZDGsENwQTuGU1kLjxwz7DWUqmgkoqr5K+IE1CjqywkKWwmYdF+Mk/Jz4nJosCUIcjHyjPBYjedHkZF4dqWxDRsRhLf9w/spRoMLmLHCTBR5gbb03l0LBlQBwxlEvKUQE6baojnWtX/Aa21CGWNh7s0G9pkGS7FYacCCblHPvnox7WgPyPmUGXQFdOYr+cwUVwUW+b9nwGqnUoCB4YivmNp+xm6RepfTNaO3QlJeJKeFV/4DlWvqnlGuFh7cG1E0xJudmKUcOQbblkmSSKoC9gxfObp3gHn/jg7VP+USn2e2mjsGWZzP2Vl0qm1/iPcA6zNusXLEFxDh7SyZ6D15sHRgJWGBJ00CfpkQzDBXXoFkfk+XEHVOMjd4VJchRG03wzcPaWWbEsJDutLJiDG7TVWiNUFu8FRMb8/ZoGZ0sLHywP3rBMQ2NInZCj6WHFLJbnStGZcpVWcEm70NfwSMwXK/MnSKCSJ7ueaXSVAuAVvW6kBw86GkAOs5oaYEzwqk9o/3SMjtQ4QNNXTeRV+hoMglfnyrTFARi46DLlp4Qu2JeVDhaAQZnWQCk7e4d0Ndw6211xB5mvJUdyxz3EBfcQr/J6TiSafzIoNzBlhu7c/zx6oZ0Rq7nC0ejNmUMcSqAplyqcIZo7f4oV0H md4LliYJ WWkOLI8meXNVaggnBJvwQLonhqaOSVd6G4S57qO1FBR+x3CT4jsWRrT65oQwj2q4W53Q35ciehl9RqmO7eJWOi+aCx9IO2Zcr5Z7PvgTEb5nTSNQxbc0r7pvtyD6blq9pKny6TLhBbBl1MUVKVNr6qDHMxkpjx3/qfM+XGyHkYu50YmXb4SJokK+2ySugKWY2dq5X74ni1gYBfFYmVmGWXd07DLs/rZQjG5QfcWwN1u01cj3B6JzP/omEsVbhcTVkOyjoJmT48uEqj3D8DYB0AJN/Q9IfEgOnTwxQDRWUKHBvpLipFxXsM2eaScvC2sKdiUbWFdbvjsCS/3p/xh0jKdLpuLdCRynXIJAE/PSn+iSs0sjwgs+ENhoil1PX84N9F0WgkIRLJ9amO7aZh9iecBiE/R22mvjLDCnZaZFpnBGPK+urwghwEe5q0w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 06, 2024 at 04:48:28AM +0200, Jason A. Donenfeld wrote: > On Thu, Sep 05, 2024 at 10:41:40PM +0200, Jason A. Donenfeld wrote: > > 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 > > > > > > Can you figure out what's going on and send a fix, which I'll squash > > > into this commit? > > > > This doesn't work, but I wonder if something like it is what we want. I > > need to head out for the day, but here's what I've got. It's all wrong > > but might be of interest. > > Oh, I just got one small detail wrong before. The below actually works, > and uses the same strategy as on arm64. > > Let me know if you'd like me to fix up this commit with the below patch, > or if you have another way you'd like to go about it. And here's the much shorter version in assembly, which maybe you prefer. Also works, and is a bit less invasive than the other thing. diff --git a/arch/powerpc/kernel/vdso/getrandom.S b/arch/powerpc/kernel/vdso/getrandom.S index a957cd2b2b03..070daba2d547 100644 --- a/arch/powerpc/kernel/vdso/getrandom.S +++ b/arch/powerpc/kernel/vdso/getrandom.S @@ -32,6 +32,14 @@ .cfi_rel_offset r2, PPC_MIN_STKFRM + STK_GOT #endif get_datapage r8 +#ifdef CONFIG_TIME_NS + lis r10, 0x7fff + ori r10, r10, 0xffff + lwz r9, VDSO_DATA_OFFSET + 4(r8) + cmpw r9, r10 + bne +8 + addi r8, r8, (1 << CONFIG_PAGE_SHIFT) +#endif addi r8, r8, VDSO_RNG_DATA_OFFSET bl CFUNC(DOTSYM(\funct)) PPC_LL r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)