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In-Reply-To: <45c8bfbf-42d2-c9d9-d246-0ffd6fc4668c@polymtl.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-11.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 7/26/23 1:45 PM, Simon Marchi wrote: >> diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c >> index 554c1455a5f..f27efbb1d59 100644 >> --- a/gdb/i386-linux-tdep.c >> +++ b/gdb/i386-linux-tdep.c >> @@ -638,45 +638,51 @@ static int i386_linux_sc_reg_offset[] = >> 0 * 4 /* %gs */ >> }; >> >> -/* Get XSAVE extended state xcr0 from core dump. */ >> +/* See i386-linux-tdep.h. */ >> >> uint64_t >> -i386_linux_core_read_xcr0 (bfd *abfd) >> +i386_linux_core_read_xsave_info (bfd *abfd, x86_xsave_layout &layout) >> { >> asection *xstate = bfd_get_section_by_name (abfd, ".reg-xstate"); >> - uint64_t xcr0; >> + if (xstate == nullptr) >> + return X86_XSTATE_SSE_MASK; >> >> - if (xstate) >> + /* Check extended state size. */ >> + size_t size = bfd_section_size (xstate); >> + if (size < X86_XSTATE_AVX_SIZE) >> + return X86_XSTATE_SSE_MASK; >> + >> + char contents[8]; >> + if (! bfd_get_section_contents (abfd, xstate, contents, >> + I386_LINUX_XSAVE_XCR0_OFFSET, 8)) >> { >> - size_t size = bfd_section_size (xstate); >> - >> - /* Check extended state size. */ >> - if (size < X86_XSTATE_AVX_SIZE) >> - xcr0 = X86_XSTATE_SSE_MASK; >> - else >> - { >> - char contents[8]; >> - >> - if (! bfd_get_section_contents (abfd, xstate, contents, >> - I386_LINUX_XSAVE_XCR0_OFFSET, >> - 8)) >> - { >> - warning (_("Couldn't read `xcr0' bytes from " >> - "`.reg-xstate' section in core file.")); >> - return 0; >> - } >> - >> - xcr0 = bfd_get_64 (abfd, contents); >> - } >> + warning (_("Couldn't read `xcr0' bytes from " >> + "`.reg-xstate' section in core file.")); >> + return X86_XSTATE_SSE_MASK; >> } >> - else >> - xcr0 = 0; >> + >> + uint64_t xcr0 = bfd_get_64 (abfd, contents); >> + >> + if (!i387_set_xsave_layout (xcr0, size, layout)) >> + return X86_XSTATE_SSE_MASK; >> >> return xcr0; >> } > > I think I spotted a change of behavior in > i386_linux_core_read_xsave_info, which has consequences down the line. > > If there's no .reg-xstate section, we would previously return xcr0 == 0, > i386_linux_read_description would return nullptr, and we would choose > between X87 and SSE based on .reg-xfp. > > After the patch, i386_linux_core_read_xsave_info returns SSE, meaning > we'll never reach the point that checks for .reg-xfp. > > Maybe the first return (if there's not .reg-xstate section) should > return 0? Ooo, that's a good catch. This function is shared with amd64, so I think it's best if it keeps returning an xcr0 value, but we could patch i386_linux_core_read_description to instead do this: static const struct target_desc * i386_linux_core_read_description (struct gdbarch *gdbarch, struct target_ops *target, bfd *abfd) { /* Linux/i386. */ x86_xsave_layout layout; uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, layout); if (xcr0 == X86_XSTATE_X87_MASK && bfd_get_section_by_name (abfd, ".reg-xfp") != NULL) xcr0 = X86_XSTATE_SSE_MASK; return i386_linux_read_description (xcr0); } -- John Baldwin