diff options
Diffstat (limited to 'common/backtrace')
| -rw-r--r-- | common/backtrace/backtrace.c | 266 | ||||
| -rw-r--r-- | common/backtrace/backtrace.mk | 31 |
2 files changed, 297 insertions, 0 deletions
diff --git a/common/backtrace/backtrace.c b/common/backtrace/backtrace.c new file mode 100644 index 0000000..f994ae5 --- /dev/null +++ b/common/backtrace/backtrace.c @@ -0,0 +1,266 @@ +/* + * Copyright (c) 2018-2022, ARM Limited and Contributors. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + */ + +#include <assert.h> +#include <stdbool.h> +#include <stdint.h> + +#include <arch_helpers.h> +#include <common/debug.h> +#include <drivers/console.h> + +/* Maximum number of entries in the backtrace to display */ +#define UNWIND_LIMIT 20U + +/* + * If -fno-omit-frame-pointer is used: + * + * - AArch64: The AAPCS defines the format of the frame records and mandates the + * usage of r29 as frame pointer. + * + * - AArch32: The format of the frame records is not defined in the AAPCS. + * However, at least GCC and Clang use the same format. When they are forced + * to only generate A32 code (with -marm), they use r11 as frame pointer and a + * similar format as in AArch64. If interworking with T32 is enabled, the + * frame pointer is r7 and the format is different. This is not supported by + * this implementation of backtrace, so it is needed to use -marm. + */ + +/* Frame records form a linked list in the stack */ +struct frame_record { + /* Previous frame record in the list */ + struct frame_record *parent; + /* Return address of the function at this level */ + uintptr_t return_addr; +}; + +static inline uintptr_t extract_address(uintptr_t address) +{ + uintptr_t ret = address; + +#if ENABLE_PAUTH + /* + * When pointer authentication is enabled, the LR value saved on the + * stack contains a PAC. It must be stripped to retrieve the return + * address. + */ + + xpaci(ret); +#endif + + return ret; +} + +/* + * Returns true if the address points to a virtual address that can be read at + * the current EL, false otherwise. + */ +#ifdef __aarch64__ +static bool is_address_readable(uintptr_t address) +{ + unsigned int el = get_current_el(); + uintptr_t addr = extract_address(address); + + if (el == 3U) { + ats1e3r(addr); + } else if (el == 2U) { + ats1e2r(addr); + } else { + AT(ats1e1r, addr); + } + + isb(); + + /* If PAR.F == 1 the address translation was aborted. */ + if ((read_par_el1() & PAR_F_MASK) != 0U) + return false; + + return true; +} +#else /* !__aarch64__ */ +static bool is_address_readable(uintptr_t addr) +{ + unsigned int el = get_current_el(); + + if (el == 3U) { + write_ats1cpr(addr); + } else if (el == 2U) { + write_ats1hr(addr); + } else { + write_ats1cpr(addr); + } + + isb(); + + /* If PAR.F == 1 the address translation was aborted. */ + if ((read64_par() & PAR_F_MASK) != 0U) + return false; + + return true; +} +#endif /* __aarch64__ */ + +/* + * Returns true if all the bytes in a given object are in mapped memory and an + * LDR using this pointer would succeed, false otherwise. + */ +static bool is_valid_object(uintptr_t addr, size_t size) +{ + assert(size > 0U); + + if (addr == 0U) + return false; + + /* Detect overflows */ + if ((addr + size) < addr) + return false; + + /* A pointer not aligned properly could trigger an alignment fault. */ + if ((addr & (sizeof(uintptr_t) - 1U)) != 0U) + return false; + + /* Check that all the object is readable */ + for (size_t i = 0; i < size; i++) { + if (!is_address_readable(addr + i)) + return false; + } + + return true; +} + +/* + * Returns true if the specified address is correctly aligned and points to a + * valid memory region. + */ +static bool is_valid_jump_address(uintptr_t addr) +{ + if (addr == 0U) + return false; + + /* Check alignment. Both A64 and A32 use 32-bit opcodes */ + if ((addr & (sizeof(uint32_t) - 1U)) != 0U) + return false; + + if (!is_address_readable(addr)) + return false; + + return true; +} + +/* + * Returns true if the pointer points at a valid frame record, false otherwise. + */ +static bool is_valid_frame_record(struct frame_record *fr) +{ + return is_valid_object((uintptr_t)fr, sizeof(struct frame_record)); +} + +/* + * Adjust the frame-pointer-register value by 4 bytes on AArch32 to have the + * same layout as AArch64. + */ +static struct frame_record *adjust_frame_record(struct frame_record *fr) +{ +#ifdef __aarch64__ + return fr; +#else + return (struct frame_record *)((uintptr_t)fr - 4U); +#endif +} + +static void unwind_stack(struct frame_record *fr, uintptr_t current_pc, + uintptr_t link_register) +{ + uintptr_t call_site; + static const char *backtrace_str = "%u: %s: 0x%lx\n"; + const char *el_str = get_el_str(get_current_el()); + + if (!is_valid_frame_record(fr)) { + printf("ERROR: Corrupted frame pointer (frame record address = %p)\n", + fr); + return; + } + + call_site = extract_address(fr->return_addr); + if (call_site != link_register) { + printf("ERROR: Corrupted stack (frame record address = %p)\n", + fr); + return; + } + + /* The level 0 of the backtrace is the current backtrace function */ + printf(backtrace_str, 0U, el_str, current_pc); + + /* + * The last frame record pointer in the linked list at the beginning of + * the stack should be NULL unless stack is corrupted. + */ + for (unsigned int i = 1U; i < UNWIND_LIMIT; i++) { + /* If an invalid frame record is found, exit. */ + if (!is_valid_frame_record(fr)) + return; + /* + * A32 and A64 are fixed length so the address from where the + * call was made is the instruction before the return address, + * which is always 4 bytes before it. + */ + + call_site = extract_address(fr->return_addr) - 4U; + + /* + * If the address is invalid it means that the frame record is + * probably corrupted. + */ + if (!is_valid_jump_address(call_site)) + return; + + printf(backtrace_str, i, el_str, call_site); + + fr = adjust_frame_record(fr->parent); + } + + printf("ERROR: Max backtrace depth reached\n"); +} + +/* + * Display a backtrace. The cookie string parameter is displayed along the + * trace to help filter the log messages. + * + * Many things can prevent displaying the expected backtrace. For example, + * compiler optimizations can use a branch instead of branch with link when it + * detects a tail call. The backtrace level for this caller will not be + * displayed, as it does not appear in the call stack anymore. Also, assembly + * functions will not be displayed unless they setup AAPCS compliant frame + * records on AArch64 and compliant with GCC-specific frame record format on + * AArch32. + * + * Usage of the trace: addr2line can be used to map the addresses to function + * and source code location when given the ELF file compiled with debug + * information. The "-i" flag is highly recommended to improve display of + * inlined function. The *.dump files generated when building each image can + * also be used. + * + * WARNING: In case of corrupted stack, this function could display security + * sensitive information past the beginning of the stack so it must not be used + * in production build. This function is only compiled in when ENABLE_BACKTRACE + * is set to 1. + */ +void backtrace(const char *cookie) +{ + uintptr_t return_address = (uintptr_t)__builtin_return_address(0U); + struct frame_record *fr = __builtin_frame_address(0U); + + /* Printing the backtrace may crash the system, flush before starting */ + console_flush(); + + fr = adjust_frame_record(fr); + + printf("BACKTRACE: START: %s\n", cookie); + + unwind_stack(fr, (uintptr_t)&backtrace, return_address); + + printf("BACKTRACE: END: %s\n", cookie); +} diff --git a/common/backtrace/backtrace.mk b/common/backtrace/backtrace.mk new file mode 100644 index 0000000..e669331 --- /dev/null +++ b/common/backtrace/backtrace.mk @@ -0,0 +1,31 @@ +# +# Copyright (c) 2018, ARM Limited and Contributors. All rights reserved. +# +# SPDX-License-Identifier: BSD-3-Clause +# + +# Enable backtrace by default in DEBUG AArch64 builds +ifeq (${ARCH},aarch32) + ENABLE_BACKTRACE := 0 +else + ENABLE_BACKTRACE := ${DEBUG} +endif + +ifeq (${ENABLE_BACKTRACE},1) + # Force the compiler to include the frame pointer + TF_CFLAGS += -fno-omit-frame-pointer + + BL_COMMON_SOURCES += common/backtrace/backtrace.c +endif + +ifeq (${ARCH},aarch32) + ifeq (${ENABLE_BACKTRACE},1) + ifneq (${AARCH32_INSTRUCTION_SET},A32) + $(error Error: AARCH32_INSTRUCTION_SET=A32 is needed \ + for ENABLE_BACKTRACE when compiling for AArch32.) + endif + endif +endif + +$(eval $(call assert_boolean,ENABLE_BACKTRACE)) +$(eval $(call add_define,ENABLE_BACKTRACE)) |