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Diffstat (limited to 'documentation/ovmf_with_gdb_16_5_2022.txt')
| -rw-r--r-- | documentation/ovmf_with_gdb_16_5_2022.txt | 171 |
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diff --git a/documentation/ovmf_with_gdb_16_5_2022.txt b/documentation/ovmf_with_gdb_16_5_2022.txt new file mode 100644 index 0000000..c5b8b7a --- /dev/null +++ b/documentation/ovmf_with_gdb_16_5_2022.txt @@ -0,0 +1,171 @@ +https://retrage.github.io/2019/12/05/debugging-ovmf-en.html + + +Building EDK2 +Build EDK2 using gcc as usual. + +$ git clone git@github.com:tianocore/edk2.git +$ cd edk2 +$ git submodule update --init --recursive +$ make -C BaseTools +$ source ./edksetup.sh +$ build -p OvmfPkg/OvmfPkgX64.dsc -b DEBUG -a X64 -t GCC5 +To make debugging easy, create a Makefile as follow. Note that we have to connect debugcon at 0x402 to dump debug information (debug.log) from OVMF[4]. + +#!/usr/bin/env make + +SHELL=/bin/bash + +LOG=debug.log +OVMFBASE=edk2/Build/OvmfX64/DEBUG_GCC5/ +OVMFCODE=$(OVMFBASE)/FV/OVMF_CODE.fd +OVMFVARS=$(OVMFBASE)/FV/OVMF_VARS.fd +QEMU=qemu-system-x86_64 +QEMUFLAGS=-drive format=raw,file=fat:rw:image \ + -drive if=pflash,format=raw,readonly,file=$(OVMFCODE) \ + -drive if=pflash,format=raw,file=$(OVMFVARS) \ + -debugcon file:$(LOG) -global isa-debugcon.iobase=0x402 \ + -serial stdio \ + -nographic \ + -nodefaults + +run: + $(QEMU) $(QEMUFLAGS) + +debug: + $(QEMU) $(QEMUFLAGS) -s -S + +.PHONY: run debug +Before debugging, run the firmware to get debug.log. It may be better to provide startup.nsh script. + +$ make run +Now, we have debug.log. It includes the addresses of loaded UEFI images like this: + +Loading PEIM at 0x00007EA8000 EntryPoint=0x00007EAB0BC DxeCore.efi +Next, extract text section (.text) RVA from *.efi PE binaries. This can be done by readelf if it is ELF, but the images are PE format. Here we use retrage/peinfo[3]. + +$ git clone git@github.com:retrage/peinfo.git +$ cd peinfo +$ make +peinfo extracts section information from a binary. This time we want to know VirtualAddress in RVA. + +Name: .text +VirtualSize: 0x000204c0 +VirtualAddress: 0x00000240 +SizeOfRawData: 0x000204c0 +PointerToRawData: 0x00000240 +PointerToRelocations: 0x00000000 +PointerToLinenumbers: 0x00000000 +NumberOfRelocations: 0x0000 +NumberOfLinenumbers: 0x0000 +Characteristics: 0x60000020 +Run following bash script with debug.log and peinfo. This outputs a snippet of GDB script that adds symbol information (add-symbol-file). It calculates the address of UEFI image text section from base address and VirtualAddress. + +#!/bin/bash + +LOG="debug.log" +BUILD="edk2/Build/OvmfX64/DEBUG_GCC5/X64" +PEINFO="peinfo/peinfo" + +cat ${LOG} | grep Loading | grep -i efi | while read LINE; do + BASE="`echo ${LINE} | cut -d " " -f4`" + NAME="`echo ${LINE} | cut -d " " -f6 | tr -d "[:cntrl:]"`" + ADDR="`${PEINFO} ${BUILD}/${NAME} \ + | grep -A 5 text | grep VirtualAddress | cut -d " " -f2`" + TEXT="`python -c "print(hex(${BASE} + ${ADDR}))"`" + SYMS="`echo ${NAME} | sed -e "s/\.efi/\.debug/g"`" + echo "add-symbol-file ${BUILD}/${SYMS} ${TEXT}" +done +$ bash gen_symbol_offsets.sh > gdbscript +cat gdb +The generated GDB script is like this: + +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/PcdPeim.debug 0x82c380 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/ReportStatusCodeRouterPei.debug 0x831080 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/StatusCodeHandlerPei.debug 0x833100 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/PlatformPei.debug 0x835100 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/PeiCore.debug 0x7ee8240 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/DxeIpl.debug 0x7ee3240 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/S3Resume2Pei.debug 0x7edf240 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/CpuMpPei.debug 0x7ed6240 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/DxeCore.debug 0x7ea8240 +add-symbol-file edk2/Build/OvmfX64/DEBUG_GCC5/X64/DevicePathDxe.debug 0x7b8f240 +Now we are ready. + +$ less debug.log +... +The 0th FV start address is 0x0000082000 +... +Loading PEIM at 0x0000082BFC0 + Entry Point = 0x0000082F40A PcdPeim.efi +... + +$ make debug + +Let’s place a breakpoint at BootServices->HandleProtocol(). + +(gdb) source gdbscript +. +. +. +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/UsbBusDxe.debug" at + .text_addr = 0x6c85240 +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/UsbKbDxe.debug" at + .text_addr = 0x6cb3240 +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/UsbMassStorageDxe.debug" at + .text_addr = 0x6c6d240 +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/QemuVideoDxe.debug" at + .text_addr = 0x6c66240 +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/VirtioGpuDxe.debug" at + .text_addr = 0x6c60240 +add symbol table from file "/home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/Shell.debug" at + .text_addr = 0x64f5240 + +(gdb) info functions CoreHandleProtocol +All functions matching regular expression "CoreHandleProtocol": +File /.../edk2/MdeModulePkg/Core/Dxe/Hand/Handle.c: +EFI_STATUS CoreHandleProtocol(EFI_HANDLE, EFI_GUID *, void **); + +(gdb) info address CoreHandleProtocol +Symbol "CoreHandleProtocol" is a function at address 0x7ea4aa9. + +(gdb) b CoreHandleProtocol + +(gdb) info symbol 0x82F40A +_ModuleEntryPoint in section .text of /home/koenigr/Memtest/git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/PcdPeim.debug + +(gdb) b *0x82F40A +Breakpoint 2 at 0x82f40a: file /home/koenigr/Memtest/git/edk2/MdePkg/Library/PeimEntryPoint/PeimEntryPoint.c, line 33. + +(gdb) target remote localhost:1234 +Remote debugging using localhost:1234 +warning: No executable has been specified and target does not support +determining executable automatically. Try using the "file" command. +0x000000000000fff0 in ?? () + +(gdb) c + +The debugger stops, and we can do source code level debug. + +!!!!!!!!!!!!!!!!!!!!!!!!!!! DOES NOT WORK !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! + + ┌──/home/akira/src/ovmf-debug/edk2/MdeModulePkg/Core/Dxe/Hand/Handle.c──────┐ + │933 CoreHandleProtocol ( │ + │934 IN EFI_HANDLE UserHandle, │ + │935 IN EFI_GUID *Protocol, │ + │936 OUT VOID **Interface │ + │937 ) │ +B+>│938 { │ + │939 return CoreOpenProtocol ( │ + │940 UserHandle, │ + │941 Protocol, │ + │942 Interface, │ + │943 gDxeCoreImageHandle, │ + │944 NULL, │ + │945 EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL │ + └───────────────────────────────────────────────────────────────────────────┘ +remote Thread 1 In: CoreHandleProtocol L938 PC: 0x7eb6ad4 + + + +(gdb) |