PR #23543 opened by catap URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23543 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/23543.patch The existing x86_32_7regs probe keeps HAVE_7REGS from relying on the EBP crash probe. HAVE_6REGS still used HAVE_EBX_AVAILABLE || HAVE_EBP_AVAILABLE, which has the same problem: an EBP clobber probe can pass even when the compiler cannot allocate the multi-register asm patterns guarded by HAVE_6REGS. Add an x86_32_6regs probe and use it for HAVE_6REGS. # Summary of changes Briefly describe what this PR does and why. <!-- If this PR requires new FATE test samples, attach them to the PR and list their target paths below (relative to the fate-suite root). Attached filenames must match the sample's filename: ```fate-samples # e.g. vorbis/new-sample.ogg ``` --> From a267e61bca0a1c47fd3266d62bbe0a75c015fe12 Mon Sep 17 00:00:00 2001 From: "Kirill A. Korinsky" <kirill@korins.ky> Date: Sat, 20 Jun 2026 23:42:55 +0200 Subject: [PATCH] configure/x86: test 6-register inline asm separately The existing x86_32_7regs probe keeps HAVE_7REGS from relying on the EBP crash probe. HAVE_6REGS still used HAVE_EBX_AVAILABLE || HAVE_EBP_AVAILABLE, which has the same problem: an EBP clobber probe can pass even when the compiler cannot allocate the multi-register asm patterns guarded by HAVE_6REGS. Add an x86_32_6regs probe and use it for HAVE_6REGS. --- configure | 9 +++++++-- libavutil/x86/asm.h | 2 +- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/configure b/configure index a6bbb86807..26bf649788 100755 --- a/configure +++ b/configure @@ -2656,6 +2656,7 @@ TOOLCHAIN_FEATURES=" symver_asm_label symver_gnu_asm vfp_args + x86_32_6regs x86_32_7regs xform_asm xmm_clobbers @@ -6850,11 +6851,14 @@ EOF check_inline_asm ebx_available '""::"b"(0)' && check_inline_asm ebx_available '"":::"%ebx"' - # check whether 7 registers are available on x86-32 + # check whether 6 and 7 registers are available on x86-32 # Since https://github.com/llvm/llvm-project/commit/0d471b3f64d3116bd57c79d872f7384f..., # Clang can save/restore EBP around clobber-only asm, so the EBP - # crash probe alone can be a false positive for 7-register asm. + # crash probe alone can be a false positive for multi-register asm. + disable x86_32_6regs disable x86_32_7regs + enabled x86_32 && enabled_any ebx_available ebp_available && + check_inline_asm x86_32_6regs '"" :: "r"(0), "r"(1), "r"(2), "r"(3), "g"(4) : "%eax", "%edx"' enabled_all x86_32 ebx_available ebp_available && check_inline_asm x86_32_7regs '"" :: "r"(0), "r"(1), "r"(2), "r"(3), "g"(4), "r"(5) : "%eax", "%edx"' @@ -8519,6 +8523,7 @@ if enabled x86; then echo "EBP available ${ebp_available-no}" fi if enabled x86_32; then + echo "6 registers available ${x86_32_6regs-no}" echo "7 registers available ${x86_32_7regs-no}" fi if enabled aarch64; then diff --git a/libavutil/x86/asm.h b/libavutil/x86/asm.h index fc9f50b1a9..21b95cbba1 100644 --- a/libavutil/x86/asm.h +++ b/libavutil/x86/asm.h @@ -72,7 +72,7 @@ typedef int x86_reg; #endif #define HAVE_7REGS (ARCH_X86_64 || HAVE_X86_32_7REGS) -#define HAVE_6REGS (ARCH_X86_64 || (HAVE_EBX_AVAILABLE || HAVE_EBP_AVAILABLE)) +#define HAVE_6REGS (ARCH_X86_64 || HAVE_X86_32_6REGS) #if ARCH_X86_64 && defined(PIC) # define BROKEN_RELOCATIONS 1 -- 2.52.0