From 306b445a6d4cc9dbb46ecdf22d9585fe9fc98115 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Sun, 4 Apr 2021 22:29:34 -0400 Subject: [PATCH] gdb: fix internal error in avr_frame_unwind_cache When trying to do pretty much anything that requires unwinding a frame on AVR, we get /home/simark/src/wt/avr/gdb/trad-frame.h:143: internal-error: LONGEST trad_frame_saved_reg::addr() const: Assertion `m_kind == trad_frame_saved_reg_kind::ADDR' failed. This is likely coming from the trad-frame refactor in 098caef485a4 ("Refactor struct trad_frame_saved_regs"). Here's an example of how to reproduce it: In one terminal: $ cat test.c int foo(int x) { return x * 7; } int main() { return foo(2); } $ avr-gcc -gdwarf-4 -mmcu=atmega2560 test.c $ /tmp/simavr/bin/simavr --mcu atmega2560 -g a.out Loaded 330 .text at address 0x0 Loaded 0 .data And in another one: $ ./gdb -q -nx --data-directory=data-directory a.out -ex "tar rem :1234" -ex "b foo" -ex c -ex bt Reading symbols from a.out... Remote debugging using :1234 0x00000000 in __vectors () Breakpoint 1 at 0x110: file test.c, line 3. Note: automatically using hardware breakpoints for read-only addresses. Continuing. Breakpoint 1, foo (x=2) at test.c:3 3 return x * 7; #0 foo (x=2) at test.c:3 /home/simark/src/wt/avr/gdb/trad-frame.h:143: internal-error: LONGEST trad_frame_saved_reg::addr() const: Assertion `m_kind == trad_frame_saved_reg_kind::ADDR' failed. What the AVR code does is: 1. In avr_scan_prologue, in the block that says "First stage of the prologue scanning.", look for "push rX" instructions and note that rX is saved on the stack. But instead of putting the actual stack address directly, it puts an offset (from the previous frame's sp). 2. Back in avr_frame_unwind_cache, in the block that says "Adjust all the saved registers", adjust all these values to be real stack addresses. To check whether a register was assigned an address (and therefore if it needs adjustment), the code does: if (info->saved_regs[i].addr () > 0) Since commit 098caef485a4, it's invalid to call the `addr` getter of trad_frame_saved_reg if the register hasn't been assigned an address. Instead, the code could use the `is_addr` getter to verify if the register has been assigned an address. This is what this patch does. gdb/ChangeLog: * avr-tdep.c (avr_frame_unwind_cache): Use trad_frame_saved_reg::is_addr. Change-Id: I5803089160b829400178746c5e3bca0c1cd11c00 --- gdb/ChangeLog | 5 +++++ gdb/avr-tdep.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 21cd0f031c2..281c567a8d7 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2021-04-04 Simon Marchi + + * avr-tdep.c (avr_frame_unwind_cache): Use + trad_frame_saved_reg::is_addr. + 2021-04-02 Simon Marchi * objfiles.c (get_objfile_bfd_data): Remove objfile parameter, diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c index 018b18f3dfd..5853e692ae4 100644 --- a/gdb/avr-tdep.c +++ b/gdb/avr-tdep.c @@ -1037,7 +1037,7 @@ avr_frame_unwind_cache (struct frame_info *this_frame, /* Adjust all the saved registers so that they contain addresses and not offsets. */ for (i = 0; i < gdbarch_num_regs (gdbarch) - 1; i++) - if (info->saved_regs[i].addr () > 0) + if (info->saved_regs[i].is_addr ()) info->saved_regs[i].set_addr (info->prev_sp - info->saved_regs[i].addr ()); -- 2.30.2