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Differential D62577 Diff 202099 ELF/Writer.cpp

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ELF/Writer.cpp

Show First 20 Lines • Show All 1,600 Lines • ▼ Show 20 Linestemplate <class ELFT> void Writer<ELFT>::finalizeSections() {
// Define __rel[a]_iplt_{start,end} symbols if needed. // Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols(); addRelIpltSymbols();
// RISC-V's gp can address +/- 2 KiB, set it to .sdata + 0x800 if not defined. // RISC-V's gp can address +/- 2 KiB, set it to .sdata + 0x800 if not defined.
if (Config->EMachine == EM_RISCV) if (Config->EMachine == EM_RISCV)
if (!dyn_cast_or_null<Defined>(Symtab->find("__global_pointer$"))) if (!dyn_cast_or_null<Defined>(Symtab->find("__global_pointer$")))
addOptionalRegular("__global_pointer$", findSection(".sdata"), 0x800); addOptionalRegular("__global_pointer$", findSection(".sdata"), 0x800);
if (Config->EMachine == EM_X86_64) {
grimarUnsubmitted
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i.e. how much reasonable this check is?

grimar: i.e. how much reasonable this check is?
MaskRayAuthorUnsubmitted
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In GNU linkers, _TLS_MODULE_BASE_ is defined on demand on i386/x86-64/arm/aarch64/s390. Many targets don't have an ABI for TLSDESC. If you feel we don't have to special case the TLSDESC targets that support TLSDESC, I can make this unconditional.

MaskRay: In GNU linkers, `_TLS_MODULE_BASE_` is defined on demand on i386/x86-64/arm/aarch64/s390. Many…
grimarUnsubmitted
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I am not sure. Let see what Rui think. Perhaps whitelisting was fine. Without any conditions, I think arm/aarch64 will be just broken with this change (i.e. LLD will produce broken output instead of link error it seems).

grimar: I am not sure. Let see what Rui think. Perhaps whitelisting was fine. Without any conditions, I…
// On targets that support TLSDESC, _TLS_MODULE_BASE_ is defined in such a
// way that:
//
// 1) With LD->LE relaxation: _TLS_MODULE_BASE_@tpoff = 0 (lowest address in
grimarUnsubmitted
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tlsBase -> TlsBase

grimar: `tlsBase` -> `TlsBase`
// the TLS block).
// 2) Without relaxation: it produces a dynamic TLSDESC relocation that
// computes 0.
//
// 1) is special cased in @tpoff computation. To satisfy 2), we define it as
// an absolute symbol of zero. This is different from GNU linkers which
// define _TLS_MODULE_BASE_ relative to the first TLS section.
Symbol *S = Symtab->find("_TLS_MODULE_BASE_");
if (S && S->isUndefined())
S->resolve(Defined{/*File=*/nullptr, S->getName(), STB_GLOBAL, STV_HIDDEN,
STT_TLS, /*Value=*/0, 0,
/*Section=*/nullptr});
Symtab->TlsModuleBase = S;
grimarUnsubmitted
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Should this assignment be under if (S && S->isUndefined()) check?

I am not sure how much is real (I guess not at all honestly). but if user defines his own _TLS_MODULE_BASE_ symbol, then
with the current code getTlsTpOffset would return 0 for it. It is probably not user would expect.

grimar: Should this assignment be under `if (S && S->isUndefined())` check? I am not sure how much is…
grimarUnsubmitted
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i.e.

if (S && S->isUndefined()) {
  S->resolve(Defined{/*File=*/nullptr, S->getName(), STB_GLOBAL, STV_HIDDEN,
                         STT_TLS, /*Value=*/0, 0,
                         /*Section=*/nullptr});
  Symtab->TlsModuleBase = S;
}
grimar: i.e. ``` if (S && S->isUndefined()) { S->resolve(Defined{/*File=*/nullptr, S->getName()…
}
// This responsible for splitting up .eh_frame section into // This responsible for splitting up .eh_frame section into
// pieces. The relocation scan uses those pieces, so this has to be // pieces. The relocation scan uses those pieces, so this has to be
// earlier. // earlier.
finalizeSynthetic(In.EhFrame); finalizeSynthetic(In.EhFrame);
Symtab->forEachSymbol([](Symbol *S) { Symtab->forEachSymbol([](Symbol *S) {
if (!S->IsPreemptible) if (!S->IsPreemptible)
S->IsPreemptible = computeIsPreemptible(*S); S->IsPreemptible = computeIsPreemptible(*S);
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