Author: Arthur Eubanks Date: 2024-02-12T13:41:58-08:00 New Revision: aef36ebb3b74c81589885c61b4fc066052dd9498
URL: https://github.com/llvm/llvm-project/commit/aef36ebb3b74c81589885c61b4fc066052dd9498 DIFF: https://github.com/llvm/llvm-project/commit/aef36ebb3b74c81589885c61b4fc066052dd9498.diff LOG: [clang] Remove old Linux kernel workaround for ensuring stack space (#81533) PR #71709 broke the Linux PIE build with `undefined symbol: alloca` errors. With the newly included `clang/Basic/Builtins.h` in that PR, it surfaces an issue with a combination of two previous patches. 26670dcba1609574cba5942aff78ff97b567c5f3 added `#undef alloca` so clang builtins handling of alloca would work under MSVC (unsure if this is still necessary). 194b6a3b1b1a99cc3c12c466a04320f271ebd8aa added code that calls `alloca` to workaround a Linux kernel < 4.1 bug. Given that Linux 4.1 was EOL in 2018, it should be ok to remove this workaround. Added: Modified: clang/tools/driver/cc1_main.cpp Removed: ################################################################################ diff --git a/clang/tools/driver/cc1_main.cpp b/clang/tools/driver/cc1_main.cpp index e9d2c6aad371db..b5c6be3c557bb3 100644 --- a/clang/tools/driver/cc1_main.cpp +++ b/clang/tools/driver/cc1_main.cpp @@ -78,64 +78,6 @@ static void LLVMErrorHandler(void *UserData, const char *Message, } #ifdef CLANG_HAVE_RLIMITS -#if defined(__linux__) && defined(__PIE__) -static size_t getCurrentStackAllocation() { - // If we can't compute the current stack usage, allow for 512K of command - // line arguments and environment. - size_t Usage = 512 * 1024; - if (FILE *StatFile = fopen("/proc/self/stat", "r")) { - // We assume that the stack extends from its current address to the end of - // the environment space. In reality, there is another string literal (the - // program name) after the environment, but this is close enough (we only - // need to be within 100K or so). - unsigned long StackPtr, EnvEnd; - // Disable silly GCC -Wformat warning that complains about length - // modifiers on ignored format specifiers. We want to retain these - // for documentation purposes even though they have no effect. -#if defined(__GNUC__) && !defined(__clang__) -#pragma GCC diagnostic push -#pragma GCC diagnostic ignored "-Wformat" -#endif - if (fscanf(StatFile, - "%*d %*s %*c %*d %*d %*d %*d %*d %*u %*lu %*lu %*lu %*lu %*lu " - "%*lu %*ld %*ld %*ld %*ld %*ld %*ld %*llu %*lu %*ld %*lu %*lu " - "%*lu %*lu %lu %*lu %*lu %*lu %*lu %*lu %*llu %*lu %*lu %*d %*d " - "%*u %*u %*llu %*lu %*ld %*lu %*lu %*lu %*lu %*lu %*lu %lu %*d", - &StackPtr, &EnvEnd) == 2) { -#if defined(__GNUC__) && !defined(__clang__) -#pragma GCC diagnostic pop -#endif - Usage = StackPtr < EnvEnd ? EnvEnd - StackPtr : StackPtr - EnvEnd; - } - fclose(StatFile); - } - return Usage; -} - -#include <alloca.h> - -LLVM_ATTRIBUTE_NOINLINE -static void ensureStackAddressSpace() { - // Linux kernels prior to 4.1 will sometimes locate the heap of a PIE binary - // relatively close to the stack (they are only guaranteed to be 128MiB - // apart). This results in crashes if we happen to heap-allocate more than - // 128MiB before we reach our stack high-water mark. - // - // To avoid these crashes, ensure that we have sufficient virtual memory - // pages allocated before we start running. - size_t Curr = getCurrentStackAllocation(); - const int kTargetStack = DesiredStackSize - 256 * 1024; - if (Curr < kTargetStack) { - volatile char *volatile Alloc = - static_cast<volatile char *>(alloca(kTargetStack - Curr)); - Alloc[0] = 0; - Alloc[kTargetStack - Curr - 1] = 0; - } -} -#else -static void ensureStackAddressSpace() {} -#endif - /// Attempt to ensure that we have at least 8MiB of usable stack space. static void ensureSufficientStack() { struct rlimit rlim; @@ -159,10 +101,6 @@ static void ensureSufficientStack() { rlim.rlim_cur != DesiredStackSize) return; } - - // We should now have a stack of size at least DesiredStackSize. Ensure - // that we can actually use that much, if necessary. - ensureStackAddressSpace(); } #else static void ensureSufficientStack() {} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
