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tls: Use gs segment for linux

This commit is contained in:
IndecisiveTurtle 2024-07-15 01:48:57 +03:00
parent 432defd992
commit 26f8fbf628
1 changed files with 10 additions and 28 deletions
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38
src/core/tls.cpp
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@ -9,7 +9,8 @@
#ifdef _WIN32 #ifdef _WIN32
#include <windows.h> #include <windows.h>
#else #else
#include <pthread.h> #include <asm/prctl.h> /* Definition of ARCH_* constants */
#include <sys/syscall.h> /* Definition of SYS_* constants */
#endif #endif
namespace Core { namespace Core {
@ -89,47 +90,28 @@ static void PatchFsAccess(u8* code, const TLSPattern& tls_pattern, Xbyak::CodeGe
#else #else
static pthread_key_t slot = 0; static u32 slot = 0;
void SetTcbBase(void* image_address) { void SetTcbBase(void* image_address) {
ASSERT(pthread_setspecific(slot, image_address) == 0); asm volatile("wrgsbase %0" :: "r" (image_address) : "memory");
} }
Tcb* GetTcbBase() { Tcb* GetTcbBase() {
return reinterpret_cast<Tcb*>(pthread_getspecific(slot)); Tcb* tcb;
asm volatile("rdgsbase %0" : "=r" (tcb) :: "memory");
return tcb;
} }
static void AllocTcbKey() { static void AllocTcbKey() {}
ASSERT(pthread_key_create(&slot, nullptr) == 0);
}
static void PatchFsAccess(u8* code, const TLSPattern& tls_pattern, Xbyak::CodeGenerator& c) { static void PatchFsAccess(u8* code, const TLSPattern& tls_pattern, Xbyak::CodeGenerator& c) {
using namespace Xbyak::util; using namespace Xbyak::util;
const auto total_size = tls_pattern.pattern_size + tls_pattern.imm_size; const auto total_size = tls_pattern.pattern_size + tls_pattern.imm_size;
// Replace mov instruction with near jump to the trampoline. // Replace fs read with gs read.
static constexpr u32 NearJmpSize = 5;
auto patch = Xbyak::CodeGenerator(total_size, code); auto patch = Xbyak::CodeGenerator(total_size, code);
patch.jmp(c.getCurr(), Xbyak::CodeGenerator::LabelType::T_NEAR);
patch.nop(total_size - NearJmpSize);
// Write the trampoline.
// The following logic is based on the glibc implementation of pthread_getspecific
// https://github.com/bminor/glibc/blob/29807a27/nptl/pthread_getspecific.c#L23
static constexpr u32 PthreadKeySecondLevelSize = 32;
static constexpr u32 PthreadSpecificOffset = 0x510;
static constexpr u32 PthreadKeyDataSize = 16;
ASSERT(slot >= PthreadKeySecondLevelSize);
const u32 idx1st = slot / PthreadKeySecondLevelSize;
const u32 idx2nd = slot % PthreadKeySecondLevelSize;
const auto target_reg = Xbyak::Reg64(tls_pattern.target_reg); const auto target_reg = Xbyak::Reg64(tls_pattern.target_reg);
c.mov(target_reg, PthreadSpecificOffset); patch.putSeg(gs);
c.putSeg(fs);
c.mov(target_reg, qword[target_reg + idx1st * 8]); // Load first level specific array.
c.mov(target_reg, qword[target_reg + idx2nd * 16 +
8]); // Load data member of pthread_key_data our slot specifies.
c.jmp(code + total_size); // Return to the instruction right after the mov.
} }
#endif #endif