From af0d0f34d8bf7482e598308b54e7ba0ae9b0c349 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Sat, 11 Feb 2023 09:04:51 +0100 Subject: [PATCH] [gdb/tdep] Don't use i386 unwinder for amd64 For i386 we have these unwinders: ... $ gdb -q -batch -ex "set arch i386" -ex "maint info frame-unwinders" The target architecture is set to "i386". dummy DUMMY_FRAME dwarf2 tailcall TAILCALL_FRAME inline INLINE_FRAME i386 epilogue NORMAL_FRAME dwarf2 NORMAL_FRAME dwarf2 signal SIGTRAMP_FRAME i386 stack tramp NORMAL_FRAME i386 sigtramp SIGTRAMP_FRAME i386 prologue NORMAL_FRAME ... and for amd64: ... $ gdb -q -batch -ex "set arch i386:x86-64" -ex "maint info frame-unwinders" The target architecture is set to "i386:x86-64". dummy DUMMY_FRAME dwarf2 tailcall TAILCALL_FRAME inline INLINE_FRAME python NORMAL_FRAME amd64 epilogue NORMAL_FRAME i386 epilogue NORMAL_FRAME dwarf2 NORMAL_FRAME dwarf2 signal SIGTRAMP_FRAME amd64 sigtramp SIGTRAMP_FRAME amd64 prologue NORMAL_FRAME i386 stack tramp NORMAL_FRAME i386 sigtramp SIGTRAMP_FRAME i386 prologue NORMAL_FRAME ... ISTM me there's no reason for the i386 unwinders to be there for amd64. Furthermore, there's a generic need to play around with enabling and disabling unwinders, see PR8434. Currently, that's only available for both the dwarf2 unwinders at once using "maint set dwarf unwinders on/off". If I manually disable the "amd64 epilogue" unwinder, the "i386 epilogue" unwinder becomes active and gives the wrong answer, while I'm actually interested in the result of the dwarf2 unwinder. Of course I can also manually disable the "i386 epilogue", but I take the fact that I have to do that as evidence that on amd64, the "i386 epilogue" is not only unnecessary, but in the way. Fix this by only adding the i386 unwinders if "info.bfd_arch_info->bits_per_word == 32". Note that the x32 abi (x86_64/-mx32): - has the same unwinder list as amd64 (x86_64/-m64) before this commit, - has info.bfd_arch_info->bits_per_word == 64, the same as amd64, and consequently, - has the same unwinder list as amd64 after this commit. Tested on x86_64-linux, -m64 and -m32. Not tested with -mx32. Reviewed-By: John Baldwin PR tdep/30102 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30102 --- gdb/i386-tdep.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c index 580664d2ce5..8dccae633f7 100644 --- a/gdb/i386-tdep.c +++ b/gdb/i386-tdep.c @@ -8613,7 +8613,8 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) appended to the list first, so that it supercedes the DWARF unwinder in function epilogues (where the DWARF unwinder currently fails). */ - frame_unwind_append_unwinder (gdbarch, &i386_epilogue_frame_unwind); + if (info.bfd_arch_info->bits_per_word == 32) + frame_unwind_append_unwinder (gdbarch, &i386_epilogue_frame_unwind); /* Hook in the DWARF CFI frame unwinder. This unwinder is appended to the list before the prologue-based unwinders, so that DWARF @@ -8792,9 +8793,12 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) tdep-> bnd0_regnum = -1; /* Hook in the legacy prologue-based unwinders last (fallback). */ - frame_unwind_append_unwinder (gdbarch, &i386_stack_tramp_frame_unwind); - frame_unwind_append_unwinder (gdbarch, &i386_sigtramp_frame_unwind); - frame_unwind_append_unwinder (gdbarch, &i386_frame_unwind); + if (info.bfd_arch_info->bits_per_word == 32) + { + frame_unwind_append_unwinder (gdbarch, &i386_stack_tramp_frame_unwind); + frame_unwind_append_unwinder (gdbarch, &i386_sigtramp_frame_unwind); + frame_unwind_append_unwinder (gdbarch, &i386_frame_unwind); + } /* If we have a register mapping, enable the generic core file support, unless it has already been enabled. */ -- 2.30.2