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three fix of elf file creation #1312

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ZhangHongchen1 wants to merge 4 commits into from
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three fix of elf file creation #1312

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ac6c3ef
write e_flags to the output elf file
Nov 3, 2022
a9da48e
fix up wrong rela of debug sections
Nov 7, 2022
5074275
optimize section symbol replace algorithm
Nov 17, 2022
e4732c7
reset found flag every replace loop
Nov 17, 2022
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11 changes: 8 additions & 3 deletions kpatch-build/create-diff-object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1544,6 +1544,10 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)

target_off = rela_target_offset(kelf, relasec, rela);

if (target_off >= (long)rela->sym->sec->sh.sh_size)
continue;

found = false;
/*
* Attempt to replace references to unbundled sections
* with their symbols.
Expand All @@ -1558,9 +1562,9 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)
start = sym->sym.st_value;
end = sym->sym.st_value + sym->sym.st_size;

if (is_text_section(relasec->base) &&
if (rela->type == R_X86_64_32S &&
is_text_section(relasec->base) &&
!is_text_section(sym->sec) &&
rela->type == R_X86_64_32S &&
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@jpoimboe jpoimboe Nov 8, 2022

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Please make this a separate commit.

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@ZhangHongchen1 ZhangHongchen1 Nov 17, 2022

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OK

rela->addend == (long)sym->sec->sh.sh_size &&
end == (long)sym->sec->sh.sh_size) {

Expand Down Expand Up @@ -2705,8 +2709,9 @@ static void kpatch_include_debug_sections(struct kpatch_elf *kelf)
if (!is_rela_section(sec) || !is_debug_section(sec))
continue;
list_for_each_entry_safe(rela, saferela, &sec->relas, list)
if (!rela->sym->sec->include)
if (!rela->sym->include || !rela->sym->sec->include) {
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@jpoimboe jpoimboe Nov 8, 2022

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Hm, why haven't we seen this problem on x86?

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@ZhangHongchen1 ZhangHongchen1 Nov 17, 2022 •
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Yes, I checked the compiled c file fs/aio.c of x86_64.It reference to __dyndbg using the __dyndbg + offset,it did not use the symbols in the __dyndbg section ,so it has no problem.
But LoongArch generate relas using the symbols in __dyndbg(or __verbose in old version kernel) and triggers the problem.
I think we should avoid that condition even if there is no problem now for x86_64.

list_del(&rela->list);
}
}
}

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1 change: 1 addition & 0 deletions kpatch-build/kpatch-elf.c
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Expand Up @@ -946,6 +946,7 @@ void kpatch_write_output_elf(struct kpatch_elf *kelf, Elf *elf, char *outfile,
memset(&ehout, 0, sizeof(ehout));
ehout.e_ident[EI_DATA] = eh.e_ident[EI_DATA];
ehout.e_machine = eh.e_machine;
ehout.e_flags = eh.e_flags;
ehout.e_type = eh.e_type;
ehout.e_version = EV_CURRENT;

Expand Down