Hi Jan. The problem here is that the needed functions for GDB in console are not included in bootblock. In src/console/console.c you can see:
#if CONFIG(GDB_STUB) && (ENV_ROMSTAGE || ENV_RAMSTAGE) void gdb_hw_init(void) { __gdb_hw_init(); } void gdb_tx_byte(unsigned char byte) { __gdb_tx_byte(byte); } void gdb_tx_flush(void) { __gdb_tx_flush(); } unsigned char gdb_rx_byte(void) { return __gdb_rx_byte(); } #endif In order to overcome this please give the attached patch a try. At least on my side it is able to compile with that patch. What I am currently not sure about are the static buffers and how they will work in bootblock Werner > -----Original Message----- > From: Samek, Jan <jan.sa...@siemens.com> > Sent: Thursday, July 22, 2021 6:15 PM > To: coreboot@coreboot.org > Cc: Zeh, Werner <werner....@siemens.com> > Subject: GDB stub & bootblock dependencies (CONFIG_IDT_IN_EVERY_STAGE=y) > > Hello, > > I am currently developing on Intel TGLRVP-UP3, but this should be relevant for > other TGL-based platforms and possibly all other that set > CONFIG_IDT_IN_EVERY_STAGE=y: > > When I try to use the GDB stub for my debug attempts on TGL > (CONFIG_GDB_STUB=y), I get the following 'undefined reference' errors during > the bootblock linkage process: > > src/arch/x86/exception.c:225: undefined reference to `gdb_tx_byte' > src/arch/x86/exception.c:225: undefined reference to `gdb_tx_byte' > src/arch/x86/exception.c:225: undefined reference to `gdb_tx_byte' > src/arch/x86/exception.c:230: undefined reference to `gdb_tx_flush' > src/arch/x86/exception.c:230: undefined reference to `gdb_tx_flush' > src/arch/x86/exception.c:230: undefined reference to `gdb_tx_flush' > src/arch/x86/exception.c:235: undefined reference to `gdb_rx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:225: > undefined > reference to `gdb_tx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:225: > undefined > reference to `gdb_tx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:225: > undefined > reference to `gdb_tx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:225: > undefined > reference to `gdb_tx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:235: > undefined > reference to `gdb_rx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:235: > undefined > reference to `gdb_rx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:235: > undefined > reference to `gdb_rx_byte' > util/crossgcc/xgcc/bin/i386-elf-ld.bfd: src/arch/x86/exception.c:235: > undefined > reference to `gdb_rx_byte' > > The gdb_*() functions used in exception.c are defined in > src/console/console.c. > Nevertheless, the problem with the functions in question is that they're > defined > under '#if CONFIG(GDB_STUB) && (ENV_ROMSTAGE || ENV_RAMSTAGE)' which > obviously doesn't allow them to be compiled into the bootblock code while > they're unconditionally (there's only the IDT_IN_EVERY_STAGE condition) > referenced in exception.c > > Looking at src/arch/x86/Makefile.inc (filtering out only the lines of > interest), it's > apparent that exception.c is linked in all stages when the IDT_IN_EVERY_STAGE > option is set: > > 76: bootblock-$(CONFIG_IDT_IN_EVERY_STAGE) += exception.c > 111: verstage-$(CONFIG_IDT_IN_EVERY_STAGE) += exception.c > 148: romstage-$(CONFIG_IDT_IN_EVERY_STAGE) += exception.c > 187: postcar-$(CONFIG_IDT_IN_EVERY_STAGE) += exception.c > 229: ramstage-y += exception.c > 291: smm-$(CONFIG_IDT_IN_EVERY_STAGE) += exception.c > > The behavior appears in revision > b90aba43c1405d3d2cb7cba05e68906e979dcda3 (master). > > To reproduce, > - run 'make menuconfig', > - select 'Mainboard ->Mainboard Vendor': 'Intel', > - select 'Mainboard -> Mainboard Model': 'Tiger Lake UP3 RVP', > - select 'Debugging -> GDB debugging support': 'y'. > - run 'make'. > > What do you think would be the best approach to make the GDB stub work on > these platforms? > > P.S. My bug tracker registration is currently pending an approval, I could be > able > to create a ticket afterwards. > > Regards, > Jan
gdb_stub_in_bootblock.patch
Description: gdb_stub_in_bootblock.patch
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