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fix(esp_system): prevent .eh_frame-based unwinding from looping indefinitely

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This commit is contained in:
Omar Chebib
2025-08-11 16:21:20 +08:00
parent a5bd9d2d13
commit 11f3c47b95
1 changed files with 32 additions and 13 deletions
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45
components/esp_system/eh_frame_parser.c
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@@ -1,5 +1,5 @@
/* /*
* SPDX-FileCopyrightText: 2020-2024 Espressif Systems (Shanghai) CO LTD * SPDX-FileCopyrightText: 2020-2025 Espressif Systems (Shanghai) CO LTD
* *
* SPDX-License-Identifier: Apache-2.0 * SPDX-License-Identifier: Apache-2.0
*/ */
@@ -28,6 +28,8 @@
#error "Unsupported architecture for unwinding" #error "Unsupported architecture for unwinding"
#endif #endif
#define MAX_ITERATIONS 100
/** /**
* @brief Dimension of an array (number of elements) * @brief Dimension of an array (number of elements)
*/ */
@@ -150,7 +152,7 @@ typedef struct {
/** /**
* @brief Set a register's offset (relative to CFA). * @brief Set a register's offset (relative to CFA).
* The highest bit is set to 1 to mark that this register needs to be retrived because it has been * The highest bit is set to 1 to mark that this register needs to be retrieved because it has been
* altered. * altered.
*/ */
#define ESP_EH_FRAME_SET_REG_OFFSET(offset) (0x80000000 | offset) #define ESP_EH_FRAME_SET_REG_OFFSET(offset) (0x80000000 | offset)
@@ -201,7 +203,7 @@ typedef struct {
#define ESP_EH_FRAME_GET_CFA_OFF(value) ((value) >> 8) #define ESP_EH_FRAME_GET_CFA_OFF(value) ((value) >> 8)
/** /**
* @brief Unsupported opcode value to return when exeucting 0-opcode type instructions. * @brief Unsupported opcode value to return when executing 0-opcode type instructions.
*/ */
#define ESP_EH_FRAME_UNSUPPORTED_OPCODE ((uint32_t) -1) #define ESP_EH_FRAME_UNSUPPORTED_OPCODE ((uint32_t) -1)
@@ -589,7 +591,8 @@ static inline uint32_t esp_eh_frame_execute_opcode_0(const uint32_t opcode, cons
* @param state DWARF machine state. The registers contained in the state will * @param state DWARF machine state. The registers contained in the state will
* modified accordingly to the instructions. * modified accordingly to the instructions.
* *
* @return true if the execution went fine, false if an unsupported instruction was met. * @return true if the execution went fine, false if an unsupported instruction was met or if the DWARF
* instructions were not enough (not properly generated) to reach the current location (PC).
*/ */
static bool esp_eh_frame_execute(const uint8_t* instructions, const uint32_t instructions_length, static bool esp_eh_frame_execute(const uint8_t* instructions, const uint32_t instructions_length,
const ExecutionFrame* frame, dwarf_regs* state) const ExecutionFrame* frame, dwarf_regs* state)
@@ -637,8 +640,18 @@ static bool esp_eh_frame_execute(const uint8_t* instructions, const uint32_t ins
/* As the state->location can also be modified by 0-opcode instructions (in the function) /* As the state->location can also be modified by 0-opcode instructions (in the function)
* and also because we need to break the loop (and not only the switch), let's put this * and also because we need to break the loop (and not only the switch), let's put this
* check here, after the execution of the instruction, outside of the switch block. */ * check here, after the execution of the instruction, outside of the switch block.
if (state->location >= EXECUTION_FRAME_PC(*frame)) { * We should stop executing the opcodes as soon as we go AFTER the program counter that
* interests us. For example, if we have the following DWARF instructions:
* ```
* DW_CFA_advance_loc: 2 to 40382ecc
* DW_CFA_offset: r1 (ra) at cfa-4
* DW_CFA_nop
* ```
* And out current PC is `0x40382ecc`, we MUST execute the instructions that are after it
* (until the next DW_CFA_advance_loc, where we would need to stop)
* */
if (state->location > EXECUTION_FRAME_PC(*frame)) {
break; break;
} }
} }
@@ -727,7 +740,7 @@ static uint32_t esp_eh_frame_initialize_state(const uint8_t* cie, ExecutionFrame
* @param state DWARF VM registers. * @param state DWARF VM registers.
* *
* @return Return Address of the current context. Frame has been restored to the previous context * @return Return Address of the current context. Frame has been restored to the previous context
* (before calling the function program counter is currently going throught). * (before calling the function program counter is currently going through).
*/ */
static uint32_t esp_eh_frame_restore_caller_state(const uint32_t* fde, static uint32_t esp_eh_frame_restore_caller_state(const uint32_t* fde,
ExecutionFrame* frame, ExecutionFrame* frame,
@@ -768,7 +781,7 @@ static uint32_t esp_eh_frame_restore_caller_state(const uint32_t* fde,
*/ */
bool success = esp_eh_frame_execute(instructions, instructions_length, frame, state); bool success = esp_eh_frame_execute(instructions, instructions_length, frame, state);
if (!success) { if (!success) {
/* An error occured (unsupported opcode), return PC as the return address. /* An error occurred (unsupported opcode), return PC as the return address.
* This will be tested by the caller, and the backtrace will be finished. */ * This will be tested by the caller, and the backtrace will be finished. */
return EXECUTION_FRAME_PC(*frame); return EXECUTION_FRAME_PC(*frame);
} }
@@ -799,7 +812,7 @@ static uint32_t esp_eh_frame_restore_caller_state(const uint32_t* fde,
/* If the frame was not available, it would be possible to retrieve the return address /* If the frame was not available, it would be possible to retrieve the return address
* register thanks to CIE structure. * register thanks to CIE structure.
* The return address points to the address the PC needs to jump to. It * The return address points to the address the PC needs to jump to. It
* does NOT point to the instruction where the routine call occured. * does NOT point to the instruction where the routine call occurred.
* This can cause problems with functions without epilogue (i.e. function * This can cause problems with functions without epilogue (i.e. function
* which last instruction is a function call). This happens when compiler * which last instruction is a function call). This happens when compiler
* optimization are ON or when a function is marked as "noreturn". * optimization are ON or when a function is marked as "noreturn".
@@ -840,7 +853,7 @@ static bool esp_eh_frame_missing_info(const uint32_t* fde, uint32_t pc)
/** /**
* @brief When one step of the backtrace is generated, output it to the serial. * @brief When one step of the backtrace is generated, output it to the serial.
* This function can be overriden as it is defined as weak. * This function can be overridden as it is defined as weak.
* *
* @param pc Program counter of the backtrace step. * @param pc Program counter of the backtrace step.
* @param sp Stack pointer of the backtrace step. * @param sp Stack pointer of the backtrace step.
@@ -866,7 +879,7 @@ void esp_eh_frame_print_backtrace(const void *frame_or)
ExecutionFrame frame = *((ExecutionFrame*) frame_or); ExecutionFrame frame = *((ExecutionFrame*) frame_or);
uint32_t size = 0; uint32_t size = 0;
uint8_t* enc_values = NULL; uint8_t* enc_values = NULL;
bool end_of_backtrace = false; int iterations = 0;
/* Start parsing the .eh_frame_hdr section. */ /* Start parsing the .eh_frame_hdr section. */
fde_header* header = (fde_header*) EH_FRAME_HDR_ADDR; fde_header* header = (fde_header*) EH_FRAME_HDR_ADDR;
@@ -893,7 +906,7 @@ void esp_eh_frame_print_backtrace(const void *frame_or)
const table_entry* sorted_table = (const table_entry*) enc_values; const table_entry* sorted_table = (const table_entry*) enc_values;
panic_print_str("Backtrace:"); panic_print_str("Backtrace:");
while (!end_of_backtrace) { for (iterations = 1; iterations < MAX_ITERATIONS; iterations++) {
/* Output one step of the backtrace. */ /* Output one step of the backtrace. */
esp_eh_frame_generated_step(EXECUTION_FRAME_PC(frame), EXECUTION_FRAME_SP(frame)); esp_eh_frame_generated_step(EXECUTION_FRAME_PC(frame), EXECUTION_FRAME_SP(frame));
@@ -927,13 +940,19 @@ void esp_eh_frame_print_backtrace(const void *frame_or)
uint32_t ra = esp_eh_frame_restore_caller_state(fde, &frame, &state); uint32_t ra = esp_eh_frame_restore_caller_state(fde, &frame, &state);
/* End of backtrace is reached if the stack and the PC don't change anymore. */ /* End of backtrace is reached if the stack and the PC don't change anymore. */
end_of_backtrace = (EXECUTION_FRAME_SP(frame) == prev_sp) && (EXECUTION_FRAME_PC(frame) == ra); if ((EXECUTION_FRAME_SP(frame) == prev_sp) && (EXECUTION_FRAME_PC(frame) == ra)) {
break;
}
/* Go back to the caller: update stack pointer and program counter. */ /* Go back to the caller: update stack pointer and program counter. */
EXECUTION_FRAME_PC(frame) = ra; EXECUTION_FRAME_PC(frame) = ra;
} }
panic_print_str("\r\n"); panic_print_str("\r\n");
if (iterations >= MAX_ITERATIONS) {
panic_print_str("Backtrace ended abruptly: maximum iterations reached\r\n");
}
} }
/** /**