Re: [PATCH v5 4/5] powerpc/vdso: Wire up getrandom() vDSO implementation on VDSO32

+/*

• • 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?

Jason

[1] https://git.zx2c4.com/linux-rng/commit/?h=jd/vdso-test-harness