[llvm] r201940 - MC: Support COFF string tables larger than 10MB
Nico Rieck
nico.rieck at gmail.com
Sat Feb 22 08:12:20 PST 2014
Author: nrieck
Date: Sat Feb 22 10:12:20 2014
New Revision: 201940
URL: http://llvm.org/viewvc/llvm-project?rev=201940&view=rev
Log:
MC: Support COFF string tables larger than 10MB
Offsets past the range of single-slash encoding are encoded as base64,
padded to 6 characters, and prefixed with two slashes. This encoding is
undocumented but used by MSVC.
Modified:
llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp
llvm/trunk/lib/Object/COFFObjectFile.cpp
llvm/trunk/test/MC/COFF/section-name-encoding.s
Modified: llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp?rev=201940&r1=201939&r2=201940&view=diff
==============================================================================
--- llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp (original)
+++ llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp Sat Feb 22 10:12:20 2014
@@ -468,12 +468,35 @@ void WinCOFFObjectWriter::DefineSymbol(M
}
}
+// Encode a string table entry offset in base 64, padded to 6 chars, and
+// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
+// Buffer must be at least 8 bytes large. No terminating null appended.
+static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
+ assert(Value > 9999999 && Value <= 0xFFFFFFFFF &&
+ "Illegal section name encoding for value");
+
+ static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+ "abcdefghijklmnopqrstuvwxyz"
+ "0123456789+/";
+
+ Buffer[0] = '/';
+ Buffer[1] = '/';
+
+ char* Ptr = Buffer + 7;
+ for (unsigned i = 0; i < 6; ++i) {
+ unsigned Rem = Value % 64;
+ Value /= 64;
+ *(Ptr--) = Alphabet[Rem];
+ }
+}
+
/// making a section real involves assigned it a number and putting
/// name into the string table if needed
void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
if (S.Name.size() > COFF::NameSize) {
const unsigned Max6DecimalSize = 999999;
const unsigned Max7DecimalSize = 9999999;
+ const uint64_t MaxBase64Size = 0xFFFFFFFFF; // 64^6, including 0
uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
if (StringTableEntry <= Max6DecimalSize) {
@@ -484,8 +507,11 @@ void WinCOFFObjectWriter::MakeSectionRea
char buffer[9] = { };
std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
std::memcpy(S.Header.Name, buffer, 8);
+ } else if (StringTableEntry <= MaxBase64Size) {
+ // Starting with 10,000,000, offsets are encoded as base64.
+ encodeBase64StringEntry(S.Header.Name, StringTableEntry);
} else {
- report_fatal_error("COFF string table is greater than 9,999,999 bytes.");
+ report_fatal_error("COFF string table is greater than 64 GB.");
}
} else
std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
Modified: llvm/trunk/lib/Object/COFFObjectFile.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/COFFObjectFile.cpp?rev=201940&r1=201939&r2=201940&view=diff
==============================================================================
--- llvm/trunk/lib/Object/COFFObjectFile.cpp (original)
+++ llvm/trunk/lib/Object/COFFObjectFile.cpp Sat Feb 22 10:12:20 2014
@@ -19,6 +19,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <cctype>
+#include <limits>
using namespace llvm;
using namespace object;
@@ -52,6 +53,40 @@ static error_code getObject(const T *&Ob
return object_error::success;
}
+// Decode a string table entry in base 64 (//AAAAAA). Expects \arg Str without
+// prefixed slashes.
+static bool decodeBase64StringEntry(StringRef Str, uint32_t &Result) {
+ assert(Str.size() <= 6 && "String too long, possible overflow.");
+ if (Str.size() > 6)
+ return true;
+
+ uint64_t Value = 0;
+ while (!Str.empty()) {
+ unsigned CharVal;
+ if (Str[0] >= 'A' && Str[0] <= 'Z') // 0..25
+ CharVal = Str[0] - 'A';
+ else if (Str[0] >= 'a' && Str[0] <= 'z') // 26..51
+ CharVal = Str[0] - 'a' + 26;
+ else if (Str[0] >= '0' && Str[0] <= '9') // 52..61
+ CharVal = Str[0] - '0' + 52;
+ else if (Str[0] == '+') // 62
+ CharVal = Str[0] - '+' + 62;
+ else if (Str[0] == '/') // 63
+ CharVal = Str[0] - '/' + 63;
+ else
+ return true;
+
+ Value = (Value * 64) + CharVal;
+ Str = Str.substr(1);
+ }
+
+ if (Value > std::numeric_limits<uint32_t>::max())
+ return true;
+
+ Result = static_cast<uint32_t>(Value);
+ return false;
+}
+
const coff_symbol *COFFObjectFile::toSymb(DataRefImpl Ref) const {
const coff_symbol *Addr = reinterpret_cast<const coff_symbol*>(Ref.p);
@@ -766,8 +801,13 @@ error_code COFFObjectFile::getSectionNam
// Check for string table entry. First byte is '/'.
if (Name[0] == '/') {
uint32_t Offset;
- if (Name.substr(1).getAsInteger(10, Offset))
- return object_error::parse_failed;
+ if (Name[1] == '/') {
+ if (decodeBase64StringEntry(Name.substr(2), Offset))
+ return object_error::parse_failed;
+ } else {
+ if (Name.substr(1).getAsInteger(10, Offset))
+ return object_error::parse_failed;
+ }
if (error_code EC = getString(Offset, Name))
return EC;
}
Modified: llvm/trunk/test/MC/COFF/section-name-encoding.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/COFF/section-name-encoding.s?rev=201940&r1=201939&r2=201940&view=diff
==============================================================================
--- llvm/trunk/test/MC/COFF/section-name-encoding.s (original)
+++ llvm/trunk/test/MC/COFF/section-name-encoding.s Sat Feb 22 10:12:20 2014
@@ -3,6 +3,7 @@
// Encodings for different lengths:
// [0, 8]: raw name
// (8, 999999]: base 10 string table index (/9999999)
+// (999999, 0xFFFFFFFF]: base 64 string table index (//AAAAAA)
//
// RUN: llvm-mc -triple x86_64-pc-win32 -filetype=obj %s | llvm-readobj -s | FileCheck %s
@@ -60,3 +61,28 @@ pad_sections aaaaaaaaaaaaaaaaaaaaaaaaaaa
// CHECK: Name: seven_digit (2F 31 30 30 30 30 32 39)
// CHECK: }
.section seven_digit; .long 1
+
+
+// Generate padding sections to increase the string table size to at least
+// 10,000,000 bytes.
+.macro pad_sections_ex pad
+ // 9x \pad
+ pad_sections \pad\pad\pad\pad\pad\pad\pad\pad\pad
+.endm
+
+// 1000x 'a'
+pad_sections_ex aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!
aaaaaaaaa
aaaaaaaaaaaaaaaaaaa
+
+
+// //AAmJa4 == 1000029 + 12 + (5 * (2 + (9 * 20 * 10 * 1000) + 1)) == 38*64^3 + 9*64^2 + 26*64 + 56
+// v | | v ~~~~~~~~~~~~~~~~~~ v
+// seven_digit offset v v "p0" pad NUL seperator
+// "seven_digit\0" # of pad sections
+//
+// "2F 2F 41 41 6D 4A 61 34" is "//AAmJa4", which decodes to "0 0 38 9 26 56".
+//
+// CHECK: Section {
+// CHECK: Number: 15
+// CHECK: Name: double_slash (2F 2F 41 41 6D 4A 61 34)
+// CHECK: }
+.section double_slash; .long 1
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