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Libpulp is deeply tied on x86_64 architecture. This commit factors out its code and generalize some of its concepts in order to work in other architectures. Signed-off-by: gbelinassi <[email protected]>
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@@ -23,6 +23,9 @@ AC_INIT([libpulp],[0.3.6],[[email protected]]) | |
AC_CONFIG_AUX_DIR([config]) | ||
AC_CONFIG_MACRO_DIRS([config]) | ||
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# For multiarch builds. | ||
AC_CANONICAL_TARGET | ||
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# Check for the availability of macros from autoconf-archive. | ||
AC_MSG_CHECKING([autoconf-archive availability]) | ||
m4_ifndef([AX_CHECK_COMPILE_FLAG], [ax_available="no"]) | ||
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@@ -223,15 +226,10 @@ AC_SUBST([PAGE_SIZE], [$($GETCONF PAGE_SIZE)])) | |
AC_SUBST([ULP_NOPS_LEN], [16]) | ||
AC_SUBST([PRE_NOPS_LEN], [14]) | ||
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AC_SUBST([ULP_NOPS_LEN_ENDBR64], [$(expr $ULP_NOPS_LEN + 4)]) | ||
AC_SUBST([PRE_NOPS_LEN_ENDBR64], [$(expr $PRE_NOPS_LEN + 4)]) | ||
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AC_DEFINE_UNQUOTED([ULP_NOPS_LEN], [$ULP_NOPS_LEN], | ||
[Total number of padding nops]) | ||
AC_DEFINE_UNQUOTED([PRE_NOPS_LEN], [$PRE_NOPS_LEN], | ||
[Padding nops before the entry point of functions]) | ||
AC_DEFINE_UNQUOTED([ULP_NOPS_LEN_ENDBR64], [$ULP_NOPS_LEN_ENDBR64], | ||
[Total number of padding nops when endbr64 is issued]) | ||
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AC_CONFIG_FILES([Makefile | ||
include/Makefile | ||
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#ifndef _ARCH_X86_64_H | ||
#define _ARCH_X86_64_H | ||
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/** Intel endbr64 instruction optcode. */ | ||
#define INSN_ENDBR64 0xf3, 0x0f, 0x1e, 0xfa | ||
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/** Offset of TLS pointer. */ | ||
#define TLS_DTV_OFFSET 0 | ||
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/** Struct used to store the registers in memory. */ | ||
typedef struct user_regs_struct registers_t; | ||
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/** Register in which the function stores the return value. */ | ||
#define FUNCTION_RETURN_REG(reg) ((reg).rax) | ||
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/** Register which acts as a program counter. */ | ||
#define PROGRAM_COUNTER_REG(reg) ((reg).rip) | ||
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/** Register which acts as top of stack. */ | ||
#define STACK_TOP_REG(reg) ((reg).rsp) | ||
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/** Set the GLOBAL ENTRYPOINT REGISTER, which in x86_64 doesn't exist. */ | ||
#define SET_GLOBAL_ENTRYPOINT_REG(reg, val) | ||
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/** Program load bias, which can be recovered by running `ld --verbose`. */ | ||
#define EXECUTABLE_START 0x400000UL | ||
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/** The red zone. */ | ||
#define RED_ZONE_LEN 128 | ||
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/** File name of the dynamic loader. */ | ||
#define LD_LINUX "ld-linux-x86-64.so.2" | ||
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/** | ||
* Number of bytes that the kernel subtracts from the program counter, | ||
* when an ongoing syscall gets interrupted and must be restarted. | ||
*/ | ||
#define RESTART_SYSCALL_SIZE 2 | ||
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#endif |
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/* | ||
* libpulp - User-space Livepatching Library | ||
* | ||
* Copyright (C) 2017-2024 SUSE Software Solutions GmbH | ||
* | ||
* This file is part of libpulp. | ||
* | ||
* libpulp is free software; you can redistribute it and/or | ||
* modify it under the terms of the GNU Lesser General Public | ||
* License as published by the Free Software Foundation; either | ||
* version 2.1 of the License, or (at your option) any later version. | ||
* | ||
* libpulp is distributed in the hope that it will be useful, | ||
* but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
* Lesser General Public License for more details. | ||
* | ||
* You should have received a copy of the GNU General Public License | ||
* along with libpulp. If not, see <http://www.gnu.org/licenses/>. | ||
*/ | ||
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#define _GNU_SOURCE | ||
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#include <stddef.h> | ||
#include <string.h> | ||
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#include "config.h" | ||
#include "error.h" | ||
#include "msg_queue.h" | ||
#include "ulp.h" | ||
#include "arch/x86_64/arch_common.h" | ||
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/** Intel endbr64 instruction optcode. */ | ||
static const uint8_t insn_endbr64[] = {INSN_ENDBR64}; | ||
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/* clang-format off */ | ||
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/** Offset of the data entry in the ulp_prologue. */ | ||
#define ULP_DATA_OFFSET 6 // ------------------------------+ | ||
// | | ||
static char ulp_prologue[ULP_NOPS_LEN] = { // | | ||
// Preceding nops | | ||
0xff, 0x25, 0, 0, 0, 0, // jmp 0x0(%rip) <-------+ | | ||
0, 0, 0, 0, 0, 0, 0, 0, // <data> &__ulp_prolog | <-+ | ||
// Function entry is here | | ||
0xeb, -(PRE_NOPS_LEN + 2) // jmp ----------------------+ | ||
// (+2 because the previous jump consumes 2 bytes. | ||
}; | ||
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#define ULP_NOPS_LEN_ENDBR64 (ULP_NOPS_LEN + 4) | ||
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/** Offset of the data entry in the ulp_prologue. */ | ||
static char ulp_prologue_endbr64[ULP_NOPS_LEN_ENDBR64] = { | ||
// Preceding nops | ||
0xff, 0x25, 0, 0, 0, 0, // jmp 0x0(%rip) <-------+ | ||
0, 0, 0, 0, 0, 0, 0, 0, // <data> &__ulp_prolog | | ||
// Function entry is here | | ||
INSN_ENDBR64, // endbr64 | | ||
0xeb, -(PRE_NOPS_LEN + 2 + 4) // jmp ----------------------+ | ||
// (+2 because the previous jump consumes 2 bytes. | ||
}; | ||
/* clang-format on */ | ||
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/** @brief Write new function address into data prologue of `old_fentry`. | ||
* | ||
* This function replaces the `<data>` section in prologue `old_fentry` | ||
* with a pointer to the new function given by `manager`, which will | ||
* replace the to be patched function. | ||
* | ||
* @param old_fentry Pointer to prologue of to be replaced function | ||
* @param manager Address of new function. | ||
*/ | ||
void | ||
ulp_patch_addr_absolute(void *old_fentry, void *manager) | ||
{ | ||
char *dst = (char *)old_fentry + ULP_DATA_OFFSET; | ||
memwrite(dst, &manager, sizeof(void *)); | ||
} | ||
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/** @brief Copy the ulp proglogue layout into the function to be patched's | ||
* prologue | ||
* | ||
* This function copies the new code prologue into the old function prologue | ||
* in order to redirect the execution to the new function. | ||
* | ||
*/ | ||
static void | ||
ulp_patch_prologue_layout(void *old_fentry, const char *prologue, int len) | ||
{ | ||
memwrite(old_fentry, prologue, len); | ||
} | ||
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/** @brief skip the ulp prologue. | ||
* | ||
* When a function gets live patch, the nops at its entry point get replaced | ||
* with a backwards-jump to a small segment of code that redirects execution to | ||
* the new version of the function. However, when all live patches to said | ||
* function are deactivated (because the live patches have been reversed), the | ||
* need for the backwards-jump is gone. | ||
* | ||
* The following function replaces the backwards-jump with nops, thus making | ||
* the target function look like it did at the beginning of execution, i.e. | ||
* without live patches. | ||
* | ||
* @param fentry Address to write the prologue to. | ||
*/ | ||
void | ||
ulp_skip_prologue(void *fentry) | ||
{ | ||
static const char insn_nop2[] = { 0x66, 0x90 }; | ||
int bias = 0; | ||
if (memcmp(fentry, insn_endbr64, sizeof(insn_endbr64)) == 0) | ||
bias += sizeof(insn_endbr64); | ||
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/* Do not jump backwards on function entry (0x6690 is a nop on x86). */ | ||
memwrite((char *)fentry + bias, insn_nop2, sizeof(insn_nop2)); | ||
} | ||
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/** @brief Actually patch the old function with the new function | ||
* | ||
* This function will finally patch the old function pointed by `old_faddr` | ||
* with the one pointed by `new_faddr`, replacing the ulp NOP prologue with | ||
* the intended content to redirect to the new function. | ||
* | ||
* @param old_faddr Address of the old function. | ||
* @param new_faddr Address of the new function. | ||
* @param enable False to disable the redirection to the new function. | ||
* | ||
* @return 0 if success, error code otherwise. | ||
*/ | ||
int | ||
ulp_patch_addr(void *old_faddr, void *new_faddr, int enable) | ||
{ | ||
void *addr; | ||
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int ulp_nops_len; | ||
const char *prologue; | ||
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const unsigned char *as_bytes = old_faddr; | ||
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/* Check if the first instruction of old_function is endbr64. In this | ||
case, we have to handle things differently. */ | ||
if (memcmp(old_faddr, insn_endbr64, sizeof(insn_endbr64)) == 0) { | ||
ulp_nops_len = ULP_NOPS_LEN_ENDBR64; | ||
prologue = ulp_prologue_endbr64; | ||
as_bytes += sizeof(insn_endbr64); | ||
} | ||
else { | ||
ulp_nops_len = ULP_NOPS_LEN; | ||
prologue = ulp_prologue; | ||
} | ||
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/* Check if we have the two NOP sequence or a JMP ref8 insn. Else we might | ||
be attempting to patch a non-livepatchable function. */ | ||
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if (!(as_bytes[0] == 0xEB || | ||
(as_bytes[1] == 0x90 && | ||
(as_bytes[0] == 0x90 || as_bytes[0] == 0x66)))) { | ||
WARN("Function at addr %lx is not livepatchable", | ||
(unsigned long)old_faddr); | ||
return ENOPATCHABLE; | ||
} | ||
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/* Find the starting address of the pages containing the nops. */ | ||
addr = old_faddr - PRE_NOPS_LEN; | ||
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/* Actually patch the prologue. */ | ||
if (enable) { | ||
ulp_patch_prologue_layout(addr, prologue, ulp_nops_len); | ||
ulp_patch_addr_absolute(addr, new_faddr); | ||
} | ||
else { | ||
ulp_skip_prologue(old_faddr); | ||
} | ||
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return 0; | ||
} |
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