From: madvenka@linux.microsoft.com To: mark.rutland@arm.com, broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, jthierry@redhat.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list Date: Thu, 12 Aug 2021 08:24:35 -0500 [thread overview] Message-ID: <20210812132435.6143-5-madvenka@linux.microsoft.com> (raw) In-Reply-To: <20210812132435.6143-1-madvenka@linux.microsoft.com> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> SYM_CODE functions don't follow the usual calling conventions. Check if the return PC in a stack frame falls in any of these. If it does, consider the stack trace unreliable. Define a special section for unreliable functions ================================================= Define a SYM_CODE_END() macro for arm64 that adds the function address range to a new section called "sym_code_functions". Linker file =========== Include the "sym_code_functions" section under read-only data in vmlinux.lds.S. Initialization ============== Define an early_initcall() to create a sym_code_functions[] array from the linker data. Unwinder check ============== Add a reliability check in unwind_is_reliable() that compares a return PC with sym_code_functions[]. If there is a match, then return failure. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> --- arch/arm64/include/asm/linkage.h | 12 +++++++ arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/stacktrace.c | 53 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 10 ++++++ 4 files changed, 76 insertions(+) diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h index 9906541a6861..616bad74e297 100644 --- a/arch/arm64/include/asm/linkage.h +++ b/arch/arm64/include/asm/linkage.h @@ -68,4 +68,16 @@ SYM_FUNC_END_ALIAS(x); \ SYM_FUNC_END_ALIAS(__pi_##x) +/* + * Record the address range of each SYM_CODE function in a struct code_range + * in a special section. + */ +#define SYM_CODE_END(name) \ + SYM_END(name, SYM_T_NONE) ;\ + 99: ;\ + .pushsection "sym_code_functions", "aw" ;\ + .quad name ;\ + .quad 99b ;\ + .popsection + #endif diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index e4ad9db53af1..c84c71063d6e 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -21,5 +21,6 @@ extern char __exittext_begin[], __exittext_end[]; extern char __irqentry_text_start[], __irqentry_text_end[]; extern char __mmuoff_data_start[], __mmuoff_data_end[]; extern char __entry_tramp_text_start[], __entry_tramp_text_end[]; +extern char __sym_code_functions_start[], __sym_code_functions_end[]; #endif /* __ASM_SECTIONS_H */ diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index b60f8a20ba64..26dbdd4fff77 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,31 @@ #include <asm/stack_pointer.h> #include <asm/stacktrace.h> +struct code_range { + unsigned long start; + unsigned long end; +}; + +static struct code_range *sym_code_functions; +static int num_sym_code_functions; + +int __init init_sym_code_functions(void) +{ + size_t size = (unsigned long)__sym_code_functions_end - + (unsigned long)__sym_code_functions_start; + + sym_code_functions = (struct code_range *)__sym_code_functions_start; + /* + * Order it so that sym_code_functions is not visible before + * num_sym_code_functions. + */ + smp_mb(); + num_sym_code_functions = size / sizeof(struct code_range); + + return 0; +} +early_initcall(init_sym_code_functions); + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -185,6 +210,10 @@ void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) */ static bool notrace unwind_is_reliable(struct stackframe *frame) { + const struct code_range *range; + unsigned long pc; + int i; + /* * If the PC is not a known kernel text address, then we cannot * be sure that a subsequent unwind will be reliable, as we @@ -192,6 +221,30 @@ static bool notrace unwind_is_reliable(struct stackframe *frame) */ if (!__kernel_text_address(frame->pc)) return false; + + /* + * Check the return PC against sym_code_functions[]. If there is a + * match, then the consider the stack frame unreliable. + * + * As SYM_CODE functions don't follow the usual calling conventions, + * we assume by default that any SYM_CODE function cannot be unwound + * reliably. + * + * Note that this includes: + * + * - Exception handlers and entry assembly + * - Trampoline assembly (e.g., ftrace, kprobes) + * - Hypervisor-related assembly + * - Hibernation-related assembly + * - CPU start-stop, suspend-resume assembly + * - Kernel relocation assembly + */ + pc = frame->pc; + for (i = 0; i < num_sym_code_functions; i++) { + range = &sym_code_functions[i]; + if (pc >= range->start && pc < range->end) + return false; + } return true; } diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 709d2c433c5e..2bf769f45b54 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -111,6 +111,14 @@ jiffies = jiffies_64; #define TRAMP_TEXT #endif +#define SYM_CODE_FUNCTIONS \ + . = ALIGN(16); \ + .symcode : AT(ADDR(.symcode) - LOAD_OFFSET) { \ + __sym_code_functions_start = .; \ + KEEP(*(sym_code_functions)) \ + __sym_code_functions_end = .; \ + } + /* * The size of the PE/COFF section that covers the kernel image, which * runs from _stext to _edata, must be a round multiple of the PE/COFF @@ -196,6 +204,8 @@ SECTIONS swapper_pg_dir = .; . += PAGE_SIZE; + SYM_CODE_FUNCTIONS + . = ALIGN(SEGMENT_ALIGN); __init_begin = .; __inittext_begin = .; -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: madvenka@linux.microsoft.com To: mark.rutland@arm.com, broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, jthierry@redhat.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list Date: Thu, 12 Aug 2021 08:24:35 -0500 [thread overview] Message-ID: <20210812132435.6143-5-madvenka@linux.microsoft.com> (raw) In-Reply-To: <20210812132435.6143-1-madvenka@linux.microsoft.com> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> SYM_CODE functions don't follow the usual calling conventions. Check if the return PC in a stack frame falls in any of these. If it does, consider the stack trace unreliable. Define a special section for unreliable functions ================================================= Define a SYM_CODE_END() macro for arm64 that adds the function address range to a new section called "sym_code_functions". Linker file =========== Include the "sym_code_functions" section under read-only data in vmlinux.lds.S. Initialization ============== Define an early_initcall() to create a sym_code_functions[] array from the linker data. Unwinder check ============== Add a reliability check in unwind_is_reliable() that compares a return PC with sym_code_functions[]. If there is a match, then return failure. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> --- arch/arm64/include/asm/linkage.h | 12 +++++++ arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/stacktrace.c | 53 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 10 ++++++ 4 files changed, 76 insertions(+) diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h index 9906541a6861..616bad74e297 100644 --- a/arch/arm64/include/asm/linkage.h +++ b/arch/arm64/include/asm/linkage.h @@ -68,4 +68,16 @@ SYM_FUNC_END_ALIAS(x); \ SYM_FUNC_END_ALIAS(__pi_##x) +/* + * Record the address range of each SYM_CODE function in a struct code_range + * in a special section. + */ +#define SYM_CODE_END(name) \ + SYM_END(name, SYM_T_NONE) ;\ + 99: ;\ + .pushsection "sym_code_functions", "aw" ;\ + .quad name ;\ + .quad 99b ;\ + .popsection + #endif diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index e4ad9db53af1..c84c71063d6e 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -21,5 +21,6 @@ extern char __exittext_begin[], __exittext_end[]; extern char __irqentry_text_start[], __irqentry_text_end[]; extern char __mmuoff_data_start[], __mmuoff_data_end[]; extern char __entry_tramp_text_start[], __entry_tramp_text_end[]; +extern char __sym_code_functions_start[], __sym_code_functions_end[]; #endif /* __ASM_SECTIONS_H */ diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index b60f8a20ba64..26dbdd4fff77 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,31 @@ #include <asm/stack_pointer.h> #include <asm/stacktrace.h> +struct code_range { + unsigned long start; + unsigned long end; +}; + +static struct code_range *sym_code_functions; +static int num_sym_code_functions; + +int __init init_sym_code_functions(void) +{ + size_t size = (unsigned long)__sym_code_functions_end - + (unsigned long)__sym_code_functions_start; + + sym_code_functions = (struct code_range *)__sym_code_functions_start; + /* + * Order it so that sym_code_functions is not visible before + * num_sym_code_functions. + */ + smp_mb(); + num_sym_code_functions = size / sizeof(struct code_range); + + return 0; +} +early_initcall(init_sym_code_functions); + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -185,6 +210,10 @@ void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) */ static bool notrace unwind_is_reliable(struct stackframe *frame) { + const struct code_range *range; + unsigned long pc; + int i; + /* * If the PC is not a known kernel text address, then we cannot * be sure that a subsequent unwind will be reliable, as we @@ -192,6 +221,30 @@ static bool notrace unwind_is_reliable(struct stackframe *frame) */ if (!__kernel_text_address(frame->pc)) return false; + + /* + * Check the return PC against sym_code_functions[]. If there is a + * match, then the consider the stack frame unreliable. + * + * As SYM_CODE functions don't follow the usual calling conventions, + * we assume by default that any SYM_CODE function cannot be unwound + * reliably. + * + * Note that this includes: + * + * - Exception handlers and entry assembly + * - Trampoline assembly (e.g., ftrace, kprobes) + * - Hypervisor-related assembly + * - Hibernation-related assembly + * - CPU start-stop, suspend-resume assembly + * - Kernel relocation assembly + */ + pc = frame->pc; + for (i = 0; i < num_sym_code_functions; i++) { + range = &sym_code_functions[i]; + if (pc >= range->start && pc < range->end) + return false; + } return true; } diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 709d2c433c5e..2bf769f45b54 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -111,6 +111,14 @@ jiffies = jiffies_64; #define TRAMP_TEXT #endif +#define SYM_CODE_FUNCTIONS \ + . = ALIGN(16); \ + .symcode : AT(ADDR(.symcode) - LOAD_OFFSET) { \ + __sym_code_functions_start = .; \ + KEEP(*(sym_code_functions)) \ + __sym_code_functions_end = .; \ + } + /* * The size of the PE/COFF section that covers the kernel image, which * runs from _stext to _edata, must be a round multiple of the PE/COFF @@ -196,6 +204,8 @@ SECTIONS swapper_pg_dir = .; . += PAGE_SIZE; + SYM_CODE_FUNCTIONS + . = ALIGN(SEGMENT_ALIGN); __init_begin = .; __inittext_begin = .; -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-08-12 13:25 UTC|newest] Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <3f2aab69a35c243c5e97f47c4ad84046355f5b90> 2021-06-30 22:33 ` [RFC PATCH v6 0/3] arm64: Implement stack trace reliability checks madvenka 2021-06-30 22:33 ` madvenka 2021-06-30 22:33 ` [RFC PATCH v6 1/3] arm64: Improve the unwinder return value madvenka 2021-06-30 22:33 ` madvenka 2021-07-28 16:56 ` Mark Rutland 2021-07-28 16:56 ` Mark Rutland 2021-07-29 13:54 ` Madhavan T. Venkataraman 2021-07-29 13:54 ` Madhavan T. Venkataraman 2021-06-30 22:33 ` [RFC PATCH v6 2/3] arm64: Introduce stack trace reliability checks in the unwinder madvenka 2021-06-30 22:33 ` madvenka 2021-06-30 22:33 ` [RFC PATCH v6 3/3] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka 2021-06-30 22:33 ` madvenka 2021-07-28 17:25 ` Mark Rutland 2021-07-28 17:25 ` Mark Rutland 2021-07-29 14:06 ` Madhavan T. Venkataraman 2021-07-29 14:06 ` Madhavan T. Venkataraman 2021-07-29 14:52 ` Mark Brown 2021-07-29 14:52 ` Mark Brown 2021-07-29 17:07 ` Madhavan T. Venkataraman 2021-07-29 17:07 ` Madhavan T. Venkataraman 2021-07-29 15:48 ` Mark Rutland 2021-07-29 15:48 ` Mark Rutland 2021-07-29 16:27 ` Mark Brown 2021-07-29 16:27 ` Mark Brown 2021-07-29 17:09 ` Madhavan T. Venkataraman 2021-07-29 17:09 ` Madhavan T. Venkataraman 2021-07-26 13:49 ` [RFC PATCH v6 0/3] arm64: Implement stack trace reliability checks Madhavan T. Venkataraman 2021-07-26 13:49 ` Madhavan T. Venkataraman 2021-08-12 13:24 ` [RFC PATCH v7 0/4] arm64: Reorganize the unwinder and implement " madvenka 2021-08-12 13:24 ` madvenka 2021-08-12 13:24 ` [RFC PATCH v7 1/4] arm64: Make all stack walking functions use arch_stack_walk() madvenka 2021-08-12 13:24 ` madvenka 2021-08-12 15:23 ` Mark Brown 2021-08-12 15:23 ` Mark Brown 2021-08-12 16:30 ` Madhavan T. Venkataraman 2021-08-12 16:30 ` Madhavan T. Venkataraman 2021-08-12 20:59 ` kernel test robot 2021-08-12 13:24 ` [RFC PATCH v7 2/4] arm64: Reorganize the unwinder code for better consistency and maintenance madvenka 2021-08-12 13:24 ` madvenka 2021-08-12 13:24 ` [RFC PATCH v7 3/4] arm64: Introduce stack trace reliability checks in the unwinder madvenka 2021-08-12 13:24 ` madvenka 2021-08-12 13:24 ` madvenka [this message] 2021-08-12 13:24 ` [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka 2021-08-12 18:53 ` kernel test robot 2021-08-12 18:31 ` [RFC PATCH v7 0/4] arm64: Reorganize the unwinder and implement stack trace reliability checks Madhavan T. Venkataraman 2021-08-12 18:31 ` Madhavan T. Venkataraman 2021-08-12 18:45 ` Madhavan T. Venkataraman 2021-08-12 18:45 ` Madhavan T. Venkataraman 2021-08-12 18:35 ` madvenka 2021-08-12 18:35 ` madvenka 2021-08-12 18:35 ` [RFC PATCH v7 1/4] arm64: Make all stack walking functions use arch_stack_walk() madvenka 2021-08-12 18:35 ` madvenka 2021-08-12 18:35 ` [RFC PATCH v7 2/4] arm64: Reorganize the unwinder code for better consistency and maintenance madvenka 2021-08-12 18:35 ` madvenka 2021-08-12 18:35 ` [RFC PATCH v7 3/4] arm64: Introduce stack trace reliability checks in the unwinder madvenka 2021-08-12 18:35 ` madvenka 2021-08-12 18:35 ` [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka 2021-08-12 18:35 ` madvenka
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