| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <777cca2b-a650-4622-9f96-684c2530794b@csgroup.eu> Date: Sat, 12 Oct 2024 11:19:32 +0200 From: Christophe Leroy <christophe.leroy@...roup.eu> To: Michael Ellerman <mpe@...erman.id.au>, Thomas Weißschuh <thomas.weissschuh@...utronix.de> Cc: Nicholas Piggin <npiggin@...il.com>, Naveen N Rao <naveen@...nel.org>, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, Jason@...c4.com Subject: Re: [PATCH 2/2] powerpc/vdso: Implement __arch_get_vdso_rng_data() Le 11/10/2024 à 13:46, Michael Ellerman a écrit : > Christophe Leroy <christophe.leroy@...roup.eu> writes: >> Le 10/10/2024 à 11:12, Thomas Weißschuh a écrit : >>> >>> I'll try to see why this doesn't work for ppc32. >> >> PC-rel instructions only exist on very very recent powerpc CPUs (power10 ?) > > Yeah power10 or later. > >> On PPC64, ELF ABI v2 requires caller to put called function address in >> r12 and it looks like GCC uses that: >> >> 0000000000000000 <__c_kernel_getrandom>: >> 0: 3c 4c 00 00 addis r2,r12,0 >> 2: R_PPC64_REL16_HA .TOC.+0x2 >> 4: 38 42 00 00 addi r2,r2,0 >> 6: R_PPC64_REL16_LO .TOC.+0x6 >> ... >> 64: 3d 22 00 00 addis r9,r2,0 >> 66: R_PPC64_TOC16_HA _vdso_datapage+0x100 >> 68: 89 29 00 00 lbz r9,0(r9) >> 6a: R_PPC64_TOC16_LO _vdso_datapage+0x100 > > Setting up r12 is only required for calls to the global entry point > (offset 0), local calls can be made to offset 8 and use/don't require > r12 to be set. That's because local calls should already have the > correct toc pointer in r2. > > But that's not true in VDSO code. > >> Which after final link results in: >> >> 0000000000001060 <__c_kernel_getrandom>: >> 1060: 3c 4c 00 01 addis r2,r12,1 >> 1064: 38 42 8e a0 addi r2,r2,-29024 >> ... >> 10c4: 3d 22 ff fc addis r9,r2,-4 >> 10c8: 89 29 62 00 lbz r9,25088(r9) > > The call to __c_kernel_getrandom skips over the r2 setup because it's a > local call, even though we haven't setup r2 correctly: Yes indeed I forgot that. So even if the final check doesn't complain, it won't work at the end. Don't know if we could find a way to detect that and fail the build. > > 0000000000000758 <__kernel_getrandom>: > 758: 91 ff 21 f8 stdu r1,-112(r1) > 75c: a6 02 08 7c mflr r0 > 760: 91 ff 21 f8 stdu r1,-112(r1) > 764: 80 00 01 f8 std r0,128(r1) > 768: 88 00 41 f8 std r2,136(r1) > 76c: 05 00 9f 42 bcl 20,4*cr7+so,770 <__kernel_getrandom+0x18> > 770: a6 02 08 7d mflr r8 > 774: fe ff 08 3d addis r8,r8,-2 > 778: 90 f8 08 39 addi r8,r8,-1904 > 77c: fc 00 68 81 lwz r11,252(r8) > 780: ff 7f 6b 6d xoris r11,r11,32767 > 784: ff ff 6b 69 xori r11,r11,65535 > 788: 34 00 6b 7d cntlzw r11,r11 > 78c: de 5b 6b 55 rlwinm r11,r11,11,15,15 > 790: 14 5a 08 7d add r8,r8,r11 > 794: d8 02 08 39 addi r8,r8,728 > 798: 41 09 00 48 bl 10d8 <__c_kernel_getrandom+0x8> > > We could setup r2, but that would only help 64-bit. > > This also makes me notice that we have a mixture of ELF ABI v1 and v2 > code in the VDSO, depending on whether the kernel is building itself ABI > v1 or v2: > > arch/powerpc/kernel/vdso/cacheflush-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/datapage-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/getcpu-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/getrandom-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/gettimeofday-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/note-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/sigtramp64-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/vgetrandom-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/vgetrandom-chacha-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped > arch/powerpc/kernel/vdso/vgettimeofday-64.o: ELF 64-bit LSB relocatable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), not stripped > > All the asm files are ABI v1 because they historically were, and don't > say otherwise. The C code comes out as ABI v1 or v2 depending on what > we're building the kernel as. Which is a bit fishy. That's not related to VDSO it seems. There is the same thing in arch/powerpc/lib for instance: $ file arch/powerpc/lib/*.o arch/powerpc/lib/checksum_64.o: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped arch/powerpc/lib/checksum_wrappers.o: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), not stripped arch/powerpc/lib/code-patching.o: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), not stripped arch/powerpc/lib/copy_mc_64.o: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500, Unspecified or Power ELF V1 ABI, version 1 (SYSV), not stripped arch/powerpc/lib/copypage_64.o: ELF 64-bit MSB relocatable, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), not stripped ... Seems like all .c files result in a ELF V2 while some of .S files are V1 et some are V2. That's odd because the build arguments seems to be the same: # AS arch/powerpc/lib/checksum_64.o powerpc64-linux-gcc -Wp,-MMD,arch/powerpc/lib/.checksum_64.o.d -nostdinc -I./arch/powerpc/include -I./arch/powerpc/include/generated -I./include -I./arch/powerpc/include/uapi -I./arch/powerpc/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -D__KERNEL__ -I ./arch/powerpc -DHAVE_AS_ATHIGH=1 -D__ASSEMBLY__ -fno-PIE -m64 -mcpu=power8 -mabi=elfv2 -mlittle-endian -Wa,--fatal-warnings -DKBUILD_MODFILE='"arch/powerpc/lib/checksum_64"' -DKBUILD_MODNAME='"checksum_64"' -D__KBUILD_MODNAME=kmod_checksum_64 -c -o arch/powerpc/lib/checksum_64.o arch/powerpc/lib/checksum_64.S ; ./tools/objtool/objtool --mcount arch/powerpc/lib/checksum_64.o # AS arch/powerpc/lib/copypage_64.o powerpc64-linux-gcc -Wp,-MMD,arch/powerpc/lib/.copypage_64.o.d -nostdinc -I./arch/powerpc/include -I./arch/powerpc/include/generated -I./include -I./arch/powerpc/include/uapi -I./arch/powerpc/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -D__KERNEL__ -I ./arch/powerpc -DHAVE_AS_ATHIGH=1 -D__ASSEMBLY__ -fno-PIE -m64 -mcpu=power8 -mabi=elfv2 -mlittle-endian -Wa,--fatal-warnings -DKBUILD_MODFILE='"arch/powerpc/lib/copypage_64"' -DKBUILD_MODNAME='"copypage_64"' -D__KBUILD_MODNAME=kmod_copypage_64 -c -o arch/powerpc/lib/copypage_64.o arch/powerpc/lib/copypage_64.S ; ./tools/objtool/objtool --mcount arch/powerpc/lib/copypage_64.o
Powered by blists - more mailing lists