96 lines
5.1 KiB
Diff
96 lines
5.1 KiB
Diff
commit 186e7b0752d8fce1618fa37519671c834c46340e
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Author: Alexander Egorenkov <egorenar@linux.ibm.com>
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Date: Wed Dec 15 18:48:53 2021 +0100
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s390: handle R_390_PLT32DBL reloc entries in machine_apply_elf_rel()
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Starting with gcc 11.3, the C compiler will generate PLT-relative function
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calls even if they are local and do not require it. Later on during linking,
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the linker will replace all PLT-relative calls to local functions with
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PC-relative ones. Unfortunately, the purgatory code of kexec/kdump is
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not being linked as a regular executable or shared library would have been,
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and therefore, all PLT-relative addresses remain in the generated purgatory
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object code unresolved. This in turn lets kexec-tools fail with
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"Unknown rela relocation: 0x14 0x73c0901c" for such relocation types.
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Furthermore, the clang C compiler has always behaved like described above
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and this commit should fix the purgatory code built with the latter.
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Because the purgatory code is no regular executable or shared library,
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contains only calls to local functions and has no PLT, all R_390_PLT32DBL
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relocation entries can be resolved just like a R_390_PC32DBL one.
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* https://refspecs.linuxfoundation.org/ELF/zSeries/lzsabi0_zSeries/x1633.html#AEN1699
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Relocation entries of purgatory code generated with gcc 11.3
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------------------------------------------------------------
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$ readelf -r purgatory/purgatory.o
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Relocation section '.rela.text' at offset 0x6e8 contains 27 entries:
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Offset Info Type Sym. Value Sym. Name + Addend
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00000000000c 000300000013 R_390_PC32DBL 0000000000000000 .data + 2
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00000000001a 001000000014 R_390_PLT32DBL 0000000000000000 sha256_starts + 2
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000000000030 001100000014 R_390_PLT32DBL 0000000000000000 sha256_update + 2
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000000000046 001200000014 R_390_PLT32DBL 0000000000000000 sha256_finish + 2
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000000000050 000300000013 R_390_PC32DBL 0000000000000000 .data + 102
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00000000005a 001300000014 R_390_PLT32DBL 0000000000000000 memcmp + 2
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...
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000000000118 001600000014 R_390_PLT32DBL 0000000000000000 setup_arch + 2
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00000000011e 000300000013 R_390_PC32DBL 0000000000000000 .data + 2
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00000000012c 000f00000014 R_390_PLT32DBL 0000000000000000 verify_sha256_digest + 2
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000000000142 001700000014 R_390_PLT32DBL 0000000000000000
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post_verification[...] + 2
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Relocation entries of purgatory code generated with gcc 11.2
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------------------------------------------------------------
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$ readelf -r purgatory/purgatory.o
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Relocation section '.rela.text' at offset 0x6e8 contains 27 entries:
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Offset Info Type Sym. Value Sym. Name + Addend
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00000000000e 000300000013 R_390_PC32DBL 0000000000000000 .data + 2
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00000000001c 001000000013 R_390_PC32DBL 0000000000000000 sha256_starts + 2
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000000000036 001100000013 R_390_PC32DBL 0000000000000000 sha256_update + 2
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000000000048 001200000013 R_390_PC32DBL 0000000000000000 sha256_finish + 2
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000000000052 000300000013 R_390_PC32DBL 0000000000000000 .data + 102
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00000000005c 001300000013 R_390_PC32DBL 0000000000000000 memcmp + 2
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...
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00000000011a 001600000013 R_390_PC32DBL 0000000000000000 setup_arch + 2
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000000000120 000300000013 R_390_PC32DBL 0000000000000000 .data + 122
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000000000130 000f00000013 R_390_PC32DBL 0000000000000000 verify_sha256_digest + 2
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000000000146 001700000013 R_390_PC32DBL 0000000000000000 post_verification[...] + 2
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Corresponding s390 kernel discussion:
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* https://lore.kernel.org/linux-s390/20211208105801.188140-1-egorenar@linux.ibm.com/T/#u
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Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
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Reported-by: Tao Liu <ltao@redhat.com>
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Suggested-by: Philipp Rudo <prudo@redhat.com>
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Reviewed-by: Philipp Rudo <prudo@redhat.com>
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[hca@linux.ibm.com: changed commit message as requested by Philipp Rudo]
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Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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Signed-off-by: Simon Horman <horms@verge.net.au>
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diff --git a/kexec/arch/s390/kexec-elf-rel-s390.c b/kexec/arch/s390/kexec-elf-rel-s390.c
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index a5e1b73455785ae3bc3aa72b3beee13ae202e82f..91ba86a9991dad4271b834fc3b24861c40309e52 100644
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--- a/kexec/arch/s390/kexec-elf-rel-s390.c
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+++ b/kexec/arch/s390/kexec-elf-rel-s390.c
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@@ -56,6 +56,7 @@ void machine_apply_elf_rel(struct mem_ehdr *UNUSED(ehdr),
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case R_390_PC16: /* PC relative 16 bit. */
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case R_390_PC16DBL: /* PC relative 16 bit shifted by 1. */
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case R_390_PC32DBL: /* PC relative 32 bit shifted by 1. */
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+ case R_390_PLT32DBL: /* 32 bit PC rel. PLT shifted by 1. */
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case R_390_PC32: /* PC relative 32 bit. */
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case R_390_PC64: /* PC relative 64 bit. */
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val -= address;
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@@ -63,7 +64,7 @@ void machine_apply_elf_rel(struct mem_ehdr *UNUSED(ehdr),
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*(unsigned short *) loc = val;
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else if (r_type == R_390_PC16DBL)
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*(unsigned short *) loc = val >> 1;
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- else if (r_type == R_390_PC32DBL)
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+ else if (r_type == R_390_PC32DBL || r_type == R_390_PLT32DBL)
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*(unsigned int *) loc = val >> 1;
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else if (r_type == R_390_PC32)
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*(unsigned int *) loc = val;
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