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Revert "Remove insn_queue from libpulp"
Relying on /proc/self/mem to bypass mprotect issues turn out to be unreliable: the process can change into another user which does not have access to this file, hence ptrace as `ulp` being root is the only way out. This reverts commit 795c590.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| /* | ||
| * libpulp - User-space Livepatching Library | ||
| * | ||
| * Copyright (C) 2023 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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| #ifndef INSNQ_TOOL_H | ||
| #define INSNQ_TOOL_H | ||
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| #include "insn_queue.h" | ||
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| void *insnq_get_writable_area(insn_queue_t *, size_t insn_size); | ||
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| ulp_error_t insnq_insert_print(const char *string); | ||
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| ulp_error_t insnq_insert_write(void *addr, int n, const void *bytes); | ||
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| int insnq_ensure_emptiness(void); | ||
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| #endif |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,172 @@ | ||
| /* | ||
| * libpulp - User-space Livepatching Library | ||
| * | ||
| * Copyright (C) 2021 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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| #include "insn_queue.h" | ||
|
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| #include <stdio.h> | ||
| #include <string.h> | ||
| #include <unistd.h> | ||
|
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| #include "error.h" | ||
| #include "ulp_common.h" | ||
|
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| /** Global instruction queue object. */ | ||
| insn_queue_t __ulp_insn_queue = { .version = INSNQ_CURR_VERSION }; | ||
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| static int | ||
| align_to(int val, int bytes) | ||
| { | ||
| int mask = bytes - 1; | ||
| return (val + mask) & (~mask); | ||
| } | ||
|
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| /** @brief Get memory area to write an instruction to in the queue. | ||
| * | ||
| * This function will retrieve an area of memory in the queue object in which | ||
| * an instruction of size `msg_size` can be writen to. The instruction is | ||
| * appended to the end of the queue, and depending of the queue attribute | ||
| * `discard_old_content` it may return NULL if there is pending operations in | ||
| * the queue, or overwrite the instruction that is on the begining of the | ||
| * queue. In case the instruction do not fit in the queue, NULL is returned. | ||
| * | ||
| * @param queue The instruction queue object. | ||
| * @param msg_size Size of instruction to allocate area to. | ||
| * | ||
| * @return Valid pointer to write to in success, NULL otherwise. | ||
| */ | ||
| void * | ||
| insnq_get_writable_area(struct insn_queue *queue, size_t msg_size) | ||
| { | ||
| /* Write the msg_queue values in variables for briefness. */ | ||
| int num_insns = queue->num_insns; | ||
| int size = queue->size; | ||
| char *buffer = queue->buffer; | ||
|
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| /* In case the message is empty or it is too large for the buffer, don't | ||
| * bother even trying to insert it. */ | ||
| if (msg_size == 0) | ||
| return NULL; | ||
|
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| /* In case the instruction won't fit the queue, then quickly return with | ||
| NULL as answer. */ | ||
| if (msg_size + size > INSN_BUFFER_MAX) { | ||
| return NULL; | ||
| } | ||
|
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| /* Reserve area for write. This breaks strict aliasing rules, so this file | ||
| must be compiled with -fno-strict-aliasing. */ | ||
| void *ret = &buffer[size]; | ||
|
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| /* Update number of bytes. */ | ||
| size += msg_size; | ||
| num_insns++; | ||
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| /* Commit back to original object. */ | ||
|
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| queue->num_insns = num_insns; | ||
| queue->size = size; | ||
|
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| return ret; | ||
| } | ||
|
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| /** @brief Insert print instruction into the queue. | ||
| * | ||
| * @param queue The instruction queue object. | ||
| * @param string String to print. | ||
| */ | ||
| ulp_error_t | ||
| insnq_insert_print(const char *string) | ||
| { | ||
| insn_queue_t *queue = &__ulp_insn_queue; | ||
|
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| int string_size = strlen(string) + 1; | ||
| int insn_size = align_to(sizeof(struct ulp_insn_print) + string_size, 4); | ||
| struct ulp_insn_print *insn = insnq_get_writable_area(queue, insn_size); | ||
|
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| if (insn == NULL) { | ||
| set_libpulp_error_state(EINSNQ); | ||
| return EINSNQ; | ||
| } | ||
|
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| insn->base.type = ULP_INSN_PRINT; | ||
| insn->base.size = insn_size; | ||
| memcpy(insn->bytes, string, string_size); | ||
|
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| return ENONE; | ||
| } | ||
|
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| /** @brief Insert write instruction into the queue. | ||
| * | ||
| * @param queue The instruction queue object. | ||
| * @param addr Address to patch. | ||
| * @param n Number of bytes to patch. | ||
| * @param bytes Bytes to patch with. | ||
| */ | ||
| ulp_error_t | ||
| insnq_insert_write(void *addr, int n, const void *bytes) | ||
| { | ||
| insn_queue_t *queue = &__ulp_insn_queue; | ||
|
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| int insn_size = align_to(sizeof(struct ulp_insn_write) + n, 8); | ||
| struct ulp_insn_write *insn = insnq_get_writable_area(queue, insn_size); | ||
|
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| if (insn == NULL) { | ||
| set_libpulp_error_state(EINSNQ); | ||
| return EINSNQ; | ||
| } | ||
|
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| insn->base.type = ULP_INSN_WRITE; | ||
| insn->base.size = insn_size; | ||
| insn->n = n; | ||
| insn->address = (uintptr_t)addr; | ||
| memcpy(insn->bytes, bytes, n); | ||
|
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| return ENONE; | ||
| } | ||
|
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| /** @brief Ensure that the instruction queue is empty. | ||
| * | ||
| * When a livepatch is triggered, the instruction queue must be empty in order | ||
| * to safely insert instructions on it. Otherwise, this means something bad | ||
| * occured on ulp side which prevented the queue to be updated after the insns | ||
| * were executed. | ||
| * | ||
| * This function will block livepatching if not empty. | ||
| * | ||
| * @return 0 if success, anything else if not empty | ||
| * | ||
| */ | ||
| int | ||
| insnq_ensure_emptiness(void) | ||
| { | ||
| insn_queue_t *queue = &__ulp_insn_queue; | ||
|
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| if (queue->num_insns > 0 || queue->size > 0) { | ||
| WARN("WARN: instruction queue not empty. This is an indication that " | ||
| "something went wrong on ulp side."); | ||
|
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| set_libpulp_error_state(EINSNQ); | ||
| return 1; | ||
| } | ||
|
|
||
| return 0; | ||
| } |
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