maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[ELF] Move GOT/PLT relocation code closer. NFC

This commit is contained in:
Fangrui Song 2021-11-29 23:10:04 -08:00
parent 42c15c7edf
commit 5047e3a3ba
1 changed files with 26 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
lld/ELF/Relocations.cpp
View File

@ -1358,32 +1358,6 @@ static void scanReloc(InputSectionBase &sec, OffsetGetter &getOffset, RelTy *&i,
}
}
// Relax relocations.
//
// If we know that a PLT entry will be resolved within the same ELF module, we
// can skip PLT access and directly jump to the destination function. For
// example, if we are linking a main executable, all dynamic symbols that can
// be resolved within the executable will actually be resolved that way at
// runtime, because the main executable is always at the beginning of a search
// list. We can leverage that fact.
if (!sym.isPreemptible && (!sym.isGnuIFunc() || config->zIfuncNoplt)) {
if (expr != R_GOT_PC) {
// The 0x8000 bit of r_addend of R_PPC_PLTREL24 is used to choose call
// stub type. It should be ignored if optimized to R_PC.
if (config->emachine == EM_PPC && expr == R_PPC32_PLTREL)
addend &= ~0x8000;
// R_HEX_GD_PLT_B22_PCREL (call a@GDPLT) is transformed into
// call __tls_get_addr even if the symbol is non-preemptible.
if (!(config->emachine == EM_HEXAGON &&
(type == R_HEX_GD_PLT_B22_PCREL ||
type == R_HEX_GD_PLT_B22_PCREL_X ||
type == R_HEX_GD_PLT_B32_PCREL_X)))
expr = fromPlt(expr);
} else if (!isAbsoluteValue(sym)) {
expr = target->adjustGotPcExpr(type, addend, relocatedAddr);
}
}
// If the relocation does not emit a GOT or GOTPLT entry but its computation
// uses their addresses, we need GOT or GOTPLT to be created.
//
@ -1411,6 +1385,32 @@ static void scanReloc(InputSectionBase &sec, OffsetGetter &getOffset, RelTy *&i,
return;
}
// Relax relocations.
//
// If we know that a PLT entry will be resolved within the same ELF module, we
// can skip PLT access and directly jump to the destination function. For
// example, if we are linking a main executable, all dynamic symbols that can
// be resolved within the executable will actually be resolved that way at
// runtime, because the main executable is always at the beginning of a search
// list. We can leverage that fact.
if (!sym.isPreemptible && (!sym.isGnuIFunc() || config->zIfuncNoplt)) {
if (expr != R_GOT_PC) {
// The 0x8000 bit of r_addend of R_PPC_PLTREL24 is used to choose call
// stub type. It should be ignored if optimized to R_PC.
if (config->emachine == EM_PPC && expr == R_PPC32_PLTREL)
addend &= ~0x8000;
// R_HEX_GD_PLT_B22_PCREL (call a@GDPLT) is transformed into
// call __tls_get_addr even if the symbol is non-preemptible.
if (!(config->emachine == EM_HEXAGON &&
(type == R_HEX_GD_PLT_B22_PCREL ||
type == R_HEX_GD_PLT_B22_PCREL_X ||
type == R_HEX_GD_PLT_B32_PCREL_X)))
expr = fromPlt(expr);
} else if (!isAbsoluteValue(sym)) {
expr = target->adjustGotPcExpr(type, addend, relocatedAddr);
}
}
// We were asked not to generate PLT entries for ifuncs. Instead, pass the
// direct relocation on through.
if (sym.isGnuIFunc() && config->zIfuncNoplt) {