RE: [PATCH v5 1/1] gdb: avoid conversion of SIGSEGV to SIGTRAP on user breakpoints

["Aktemur, Baris" <TankutBaris.Aktemur@amd.com>]

AMD General

On Friday, August 28, 2026 3:50 PM, Klaus Gerlicher wrote:
> From: "Gerlicher, Klaus" <klaus.gerlicher@intel.com>
>
> GDB converts signals GDB_SIGNAL_ILL, GDB_SIGNAL_SEGV and GDB_SIGNAL_EMT to
> GDB_SIGNAL_TRAP if a breakpoint is inserted at the fault location.  This
> conversion logic assumes that when these signals occur at a breakpoint
> location, the signal was actually caused by hitting the breakpoint rather
> than a genuine fault.
>
> However, some architectures have "imprecise page fault reporting," where a
> memory access violation can be reported several instructions after the
> faulting instruction.  For example:
>
>   INSN1  <-- generates a SIGSEGV
>   INSN2
>   INSN3  <-- breakpoint installed here
>
> If INSN1 causes a memory access violation, the backend may report the stop
> at INSN3, where a breakpoint happens to be installed.  GDB's logic then
> incorrectly assumes "there is a breakpoint at INSN3, so this SIGSEGV must
> mean we hit the breakpoint" and converts it to SIGTRAP.  On architectures
> with imprecise fault reporting, this is wrong: if a breakpoint is never
> reported via SIGSEGV, then receiving a SIGSEGV at a breakpoint location
> means we have a genuine SIGSEGV, not a breakpoint hit.
>
> Add a new gdbarch function, imprecise_pagefault_reporting, that allows the
> signal conversion from GDB_SIGNAL_SEGV to GDB_SIGNAL_TRAP to be skipped for
> an architecture.  The default is false (conversion enabled), preserving
> existing behavior.  Architectures with imprecise fault reporting should
> override this to return true.

Looks good to me.  Thanks.

Reviewed-By: Tankut Baris Aktemur <TankutBaris.Aktemur@amd.com>

When this is merged, I'll submit a patch that overrides the gdbarch method
in the amdgpu target and includes a test.

-Baris