; The assembly below corresponds to this program: ; __attribute__((nodebug)) ; int foo() { ; return 10; ; } ; int main(int argc, char **argv) { ; foo(); ; return 0; ; } ; ; The assembly was edited in two places (search for "EDIT"): ; 1. A "orr x29, x29, #0x1000000000000000" instruction was added in foo. This ; effectively changes the CFA value of the frame above foo (i.e. main). ; 2. In main, the DWARF location of `argv` was changed to DW_AT_call_frame_cfa. ; ; This allows us to stop in foo, go to frame 1 (main) and do `v &argv`, ; obtaining the result of evaluating DW_AT_call_frame_cfa. .section __TEXT,__text,regular,pure_instructions .globl _foo ; -- Begin function foo .p2align 2 _foo: ; @foo Lfunc_begin0: .cfi_startproc orr x29, x29, #0x1000000000000000 ; EDIT: Set top byte of fp. stp x29, x30, [sp, #-16]! ; 16-byte Folded Spill mov x29, sp .cfi_def_cfa w29, 16 .cfi_offset w30, -8 .cfi_offset w29, -16 mov w0, #10 ; =0xa ldp x29, x30, [sp], #16 ; 16-byte Folded Reload ret Lfunc_end0: .cfi_endproc ; -- End function .globl _main ; -- Begin function main .p2align 2 _main: ; @main Lfunc_begin1: .file 1 "/test" "test.c" .loc 1 6 0 ; test.c:6:0 .cfi_startproc sub sp, sp, #48 stp x29, x30, [sp, #32] ; 16-byte Folded Spill add x29, sp, #32 .cfi_def_cfa w29, 16 .cfi_offset w30, -8 .cfi_offset w29, -16 mov w8, #0 ; =0x0 str w8, [sp, #12] ; 4-byte Folded Spill stur wzr, [x29, #-4] stur w0, [x29, #-8] str x1, [sp, #16] Ltmp0: bl _foo ldr w0, [sp, #12] ; 4-byte Folded Reload ldp x29, x30, [sp, #32] ; 16-byte Folded Reload add sp, sp, #48 ret Ltmp1: Lfunc_end1: .cfi_endproc ; -- End function .section __DWARF,__debug_abbrev,regular,debug Lsection_abbrev: .byte 1 ; Abbreviation Code .byte 17 ; DW_TAG_compile_unit .byte 1 ; DW_CHILDREN_yes .byte 37 ; DW_AT_producer .byte 14 ; DW_FORM_strp .byte 19 ; DW_AT_language .byte 5 ; DW_FORM_data2 .byte 3 ; DW_AT_name .byte 14 ; DW_FORM_strp .ascii "\202|" ; DW_AT_LLVM_sysroot .byte 14 ; DW_FORM_strp .ascii "\357\177" ; DW_AT_APPLE_sdk .byte 14 ; DW_FORM_strp .byte 16 ; DW_AT_stmt_list .byte 23 ; DW_FORM_sec_offset .byte 27 ; DW_AT_comp_dir .byte 14 ; DW_FORM_strp .byte 17 ; DW_AT_low_pc .byte 1 ; DW_FORM_addr .byte 18 ; DW_AT_high_pc .byte 6 ; DW_FORM_data4 .byte 0 ; EOM(1) .byte 0 ; EOM(2) .byte 2 ; Abbreviation Code .byte 46 ; DW_TAG_subprogram .byte 1 ; DW_CHILDREN_yes .byte 17 ; DW_AT_low_pc .byte 1 ; DW_FORM_addr .byte 18 ; DW_AT_high_pc .byte 6 ; DW_FORM_data4 .byte 64 ; DW_AT_frame_base .byte 24 ; DW_FORM_exprloc .byte 3 ; DW_AT_name .byte 14 ; DW_FORM_strp .byte 58 ; DW_AT_decl_file .byte 11 ; DW_FORM_data1 .byte 59 ; DW_AT_decl_line .byte 11 ; DW_FORM_data1 .byte 39 ; DW_AT_prototyped .byte 25 ; DW_FORM_flag_present .byte 73 ; DW_AT_type .byte 19 ; DW_FORM_ref4 .byte 63 ; DW_AT_external .byte 25 ; DW_FORM_flag_present .byte 0 ; EOM(1) .byte 0 ; EOM(2) .byte 3 ; Abbreviation Code .byte 5 ; DW_TAG_formal_parameter .byte 0 ; DW_CHILDREN_no .byte 2 ; DW_AT_location .byte 24 ; DW_FORM_exprloc .byte 3 ; DW_AT_name .byte 14 ; DW_FORM_strp .byte 58 ; DW_AT_decl_file .byte 11 ; DW_FORM_data1 .byte 59 ; DW_AT_decl_line .byte 11 ; DW_FORM_data1 .byte 73 ; DW_AT_type .byte 19 ; DW_FORM_ref4 .byte 0 ; EOM(1) .byte 0 ; EOM(2) .byte 4 ; Abbreviation Code .byte 36 ; DW_TAG_base_type .byte 0 ; DW_CHILDREN_no .byte 3 ; DW_AT_name .byte 14 ; DW_FORM_strp .byte 62 ; DW_AT_encoding .byte 11 ; DW_FORM_data1 .byte 11 ; DW_AT_byte_size .byte 11 ; DW_FORM_data1 .byte 0 ; EOM(1) .byte 0 ; EOM(2) .byte 5 ; Abbreviation Code .byte 15 ; DW_TAG_pointer_type .byte 0 ; DW_CHILDREN_no .byte 73 ; DW_AT_type .byte 19 ; DW_FORM_ref4 .byte 0 ; EOM(1) .byte 0 ; EOM(2) .byte 0 ; EOM(3) .section __DWARF,__debug_info,regular,debug Lsection_info: Lcu_begin0: .set Lset0, Ldebug_info_end0-Ldebug_info_start0 ; Length of Unit .long Lset0 Ldebug_info_start0: .short 4 ; DWARF version number .set Lset1, Lsection_abbrev-Lsection_abbrev ; Offset Into Abbrev. Section .long Lset1 .byte 8 ; Address Size (in bytes) .byte 1 ; Abbrev [1] 0xb:0x76 DW_TAG_compile_unit .long 0 ; DW_AT_producer .short 12 ; DW_AT_language .long 47 ; DW_AT_name .long 54 ; DW_AT_LLVM_sysroot .long 165 ; DW_AT_APPLE_sdk .set Lset2, Lline_table_start0-Lsection_line ; DW_AT_stmt_list .long Lset2 .long 180 ; DW_AT_comp_dir .quad Lfunc_begin1 ; DW_AT_low_pc .set Lset3, Lfunc_end1-Lfunc_begin1 ; DW_AT_high_pc .long Lset3 .byte 2 ; Abbrev [2] 0x32:0x36 DW_TAG_subprogram .quad Lfunc_begin1 ; DW_AT_low_pc .set Lset4, Lfunc_end1-Lfunc_begin1 ; DW_AT_high_pc .long Lset4 .byte 1 ; DW_AT_frame_base .byte 109 .long 247 ; DW_AT_name .byte 1 ; DW_AT_decl_file .byte 6 ; DW_AT_decl_line ; DW_AT_prototyped .long 107 ; DW_AT_type ; DW_AT_external .byte 3 ; Abbrev [3] 0x4b:0xe DW_TAG_formal_parameter .byte 2 ; DW_AT_location .byte 145 .byte 120 .long 256 ; DW_AT_name .byte 1 ; DW_AT_decl_file .byte 6 ; DW_AT_decl_line .long 103 ; DW_AT_type .byte 3 ; Abbrev [3] 0x59:0xe DW_TAG_formal_parameter .byte 1 ; DW_AT_location .byte 0x9c ; EDIT: DW_AT_call_frame_cfa .long 261 ; DW_AT_name .byte 1 ; DW_AT_decl_file .byte 6 ; DW_AT_decl_line .long 110 ; DW_AT_type .byte 0 ; End Of Children Mark .byte 4 ; Abbrev [4] 0x68:0x7 DW_TAG_base_type .long 252 ; DW_AT_name .byte 5 ; DW_AT_encoding .byte 4 ; DW_AT_byte_size .byte 5 ; Abbrev [5] 0x6f:0x5 DW_TAG_pointer_type .long 115 ; DW_AT_type .byte 5 ; Abbrev [5] 0x74:0x5 DW_TAG_pointer_type .long 120 ; DW_AT_type .byte 4 ; Abbrev [4] 0x79:0x7 DW_TAG_base_type .long 266 ; DW_AT_name .byte 6 ; DW_AT_encoding .byte 1 ; DW_AT_byte_size .byte 0 ; End Of Children Mark Ldebug_info_end0: .section __DWARF,__debug_str,regular,debug Linfo_string: .asciz "Apple clang " ; string offset=0 .asciz "test.c" ; string offset=47 .asciz "/Applications/Xcode..........................................................................................." ; string offset=54 .asciz ".............." ; string offset=165 .asciz "......................................................../llvm_src1" ; string offset=180 .asciz "main" ; string offset=247 .asciz "int" ; string offset=252 .asciz "argc" ; string offset=256 .asciz "argv" ; string offset=261 .asciz "char" ; string offset=266 .subsections_via_symbols .section __DWARF,__debug_line,regular,debug Lsection_line: Lline_table_start0: