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)
