include/linux/objtool.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_OBJTOOL_H
   3 #define _LINUX_OBJTOOL_H
   4
   5 #ifndef __ASSEMBLY__
   6
   7 #include <linux/types.h>
   8
   9 /*
  10  * This struct is used by asm and inline asm code to manually annotate the
  11  * location of registers on the stack.
  12  */
  13 struct unwind_hint {
  14         u32             ip;
  15         s16             sp_offset;
  16         u8              sp_reg;
  17         u8              type;
  18         u8              end;
  19 };
  20 #endif
  21
  22 /*
  23  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  24  * (the caller's SP right before it made the call).  Used for all callable
  25  * functions, i.e. all C code and all callable asm functions.
  26  *
  27  * UNWIND_HINT_TYPE_REGS: Used in entry code to indicate that sp_reg+sp_offset
  28  * points to a fully populated pt_regs from a syscall, interrupt, or exception.
  29  *
  30  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  31  * sp_reg+sp_offset points to the iret return frame.
  32  *
  33  * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
  34  * Useful for code which doesn't have an ELF function annotation.
  35  */
  36 #define UNWIND_HINT_TYPE_CALL           0
  37 #define UNWIND_HINT_TYPE_REGS           1
  38 #define UNWIND_HINT_TYPE_REGS_PARTIAL   2
  39 #define UNWIND_HINT_TYPE_FUNC           3
  40
  41 #ifdef CONFIG_STACK_VALIDATION
  42
  43 #ifndef __ASSEMBLY__
  44
  45 #define UNWIND_HINT(sp_reg, sp_offset, type, end)               \
  46         "987: \n\t"                                             \
  47         ".pushsection .discard.unwind_hints\n\t"                \
  48         /* struct unwind_hint */                                \
  49         ".long 987b - .\n\t"                                    \
  50         ".short " __stringify(sp_offset) "\n\t"                 \
  51         ".byte " __stringify(sp_reg) "\n\t"                     \
  52         ".byte " __stringify(type) "\n\t"                       \
  53         ".byte " __stringify(end) "\n\t"                        \
  54         ".balign 4 \n\t"                                        \
  55         ".popsection\n\t"
  56
  57 /*
  58  * This macro marks the given function's stack frame as "non-standard", which
  59  * tells objtool to ignore the function when doing stack metadata validation.
  60  * It should only be used in special cases where you're 100% sure it won't
  61  * affect the reliability of frame pointers and kernel stack traces.
  62  *
  63  * For more information, see tools/objtool/Documentation/stack-validation.txt.
  64  */
  65 #define STACK_FRAME_NON_STANDARD(func) \
  66         static void __used __section(".discard.func_stack_frame_non_standard") \
  67                 *__func_stack_frame_non_standard_##func = func
  68
  69 #else /* __ASSEMBLY__ */
  70
  71 /*
  72  * This macro indicates that the following intra-function call is valid.
  73  * Any non-annotated intra-function call will cause objtool to issue a warning.
  74  */
  75 #define ANNOTATE_INTRA_FUNCTION_CALL                            \
  76         999:                                                    \
  77         .pushsection .discard.intra_function_calls;             \
  78         .long 999b;                                             \
  79         .popsection;
  80
  81 /*
  82  * In asm, there are two kinds of code: normal C-type callable functions and
  83  * the rest.  The normal callable functions can be called by other code, and
  84  * don't do anything unusual with the stack.  Such normal callable functions
  85  * are annotated with the ENTRY/ENDPROC macros.  Most asm code falls in this
  86  * category.  In this case, no special debugging annotations are needed because
  87  * objtool can automatically generate the ORC data for the ORC unwinder to read
  88  * at runtime.
  89  *
  90  * Anything which doesn't fall into the above category, such as syscall and
  91  * interrupt handlers, tends to not be called directly by other functions, and
  92  * often does unusual non-C-function-type things with the stack pointer.  Such
  93  * code needs to be annotated such that objtool can understand it.  The
  94  * following CFI hint macros are for this type of code.
  95  *
  96  * These macros provide hints to objtool about the state of the stack at each
  97  * instruction.  Objtool starts from the hints and follows the code flow,
  98  * making automatic CFI adjustments when it sees pushes and pops, filling out
  99  * the debuginfo as necessary.  It will also warn if it sees any
 100  * inconsistencies.
 101  */
 102 .macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
 103 .Lunwind_hint_ip_\@:
 104         .pushsection .discard.unwind_hints
 105                 /* struct unwind_hint */
 106                 .long .Lunwind_hint_ip_\@ - .
 107                 .short \sp_offset
 108                 .byte \sp_reg
 109                 .byte \type
 110                 .byte \end
 111                 .balign 4
 112         .popsection
 113 .endm
 114
 115 .macro STACK_FRAME_NON_STANDARD func:req
 116         .pushsection .discard.func_stack_frame_non_standard, "aw"
 117                 .long \func - .
 118         .popsection
 119 .endm
 120
 121 #endif /* __ASSEMBLY__ */
 122
 123 #else /* !CONFIG_STACK_VALIDATION */
 124
 125 #ifndef __ASSEMBLY__
 126
 127 #define UNWIND_HINT(sp_reg, sp_offset, type, end)       \
 128         "\n\t"
 129 #define STACK_FRAME_NON_STANDARD(func)
 130 #else
 131 #define ANNOTATE_INTRA_FUNCTION_CALL
 132 .macro UNWIND_HINT sp_reg:req sp_offset=0 type:req end=0
 133 .endm
 134 .macro STACK_FRAME_NON_STANDARD func:req
 135 .endm
 136 #endif
 137
 138 #endif /* CONFIG_STACK_VALIDATION */
 139
 140 #endif /* _LINUX_OBJTOOL_H */