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

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Le 05/09/2024 à 18:13, Jason A. Donenfeld a écrit :
+/*
+ * 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.

Did I write that ? I can't remember and neither can I remember testing it with time namespaces.


 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.

What is the command to use to test with time namespace ?


Can you figure out what's going on and send a fix, which I'll squash
into this commit?

Sure


Jason

[1] https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.zx2c4.com%2Flinux-rng%2Fcommit%2F%3Fh%3Djd%2Fvdso-test-harness&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C59fa9061064945c73a1608dccdc5b51c%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638611496253413014%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=ZUJqhcnZL7SYkuXUIt9Nlo46sZj26VYW%2F8I%2BrBLRpBE%3D&reserved=0




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