From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTPS id F26754BBD8 for ; Mon, 3 Mar 2025 20:56:34 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id EA1C668EAE3; Mon, 3 Mar 2025 22:56:30 +0200 (EET) Received: from mail-qk1-f201.google.com (mail-qk1-f201.google.com [209.85.222.201]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id C5D4868E985 for ; Mon, 3 Mar 2025 22:56:24 +0200 (EET) Received: by mail-qk1-f201.google.com with SMTP id af79cd13be357-7c3b53373f7so435573185a.0 for ; Mon, 03 Mar 2025 12:56:24 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741035383; x=1741640183; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=+nWeUX+ekib1s2pvR+fGlJCLGpzBukWPl5GnE1yrt2Y=; b=vzxesdatndlEzoQMGdJ7P3tf+1MCwNoj4HkbCmGYMMiCWYRLcGP7f8rxVSSMfBuXw/ MIvBjLJbNo584XmJYxB9gaoiiNfZq5I9q9wr9HA8DkXDsqU1IITNTDmTbLGCzOggk039 ssHlEQpz4/mfAB64msyKlGoQlDfUIGFZFPcy7zovNb7vjWaaQWD+66gvWc0LZRIQL6ga nT1VjTrCqG6/GFIHSuZLh2N13MIQFSOzz5BXDdbM35FOa51L5wQFy+kZ5TwYfFQ1zXvT r1drzJh+60teZxLcf+9MvwMpc/Fcg6ymwYPPwOLN7SQBaJmqAyX0o/x1FaAPLoZ8hOtX 4ngQ== X-Gm-Message-State: AOJu0Yx1E8mcdWBrA9DcwmAHNLfKmyQSizlM9NvgNE3fvNKgHmzcK/r2 xf2DDGBW5Kd7KVWXp/2d6vA5s/ASUr3o6q3pvblZgfkG7iaPzlWwm+jYSuaK2NADBiTiVTcrWNr HQ8m1+qhHx8MtR/5XjONb3lyZ+NqgiXibeLjbyZ/IQWcZja0hJmINgVdnd4mbLfwwy8Iurid1JR kDedsOAhOmnMq5PiS1M41h1JI= X-Google-Smtp-Source: AGHT+IGangrOJKdgdfBUePj9hdwpQB41tBXEbXEVDEIwdicSa0BDStWgIMp0AJsulogQBJO6UGfA9I1t X-Received: from qkoz14.prod.google.com ([2002:a05:620a:260e:b0:7c0:b04f:a211]) (user=prka job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:1a8a:b0:7c0:c046:7c6b with SMTP id af79cd13be357-7c39c66d3a8mr2589468285a.53.1741035383107; Mon, 03 Mar 2025 12:56:23 -0800 (PST) Date: Mon, 3 Mar 2025 20:56:12 +0000 In-Reply-To: <20250226194437.121075-1-prka@google.com> Mime-Version: 1.0 References: <20250226194437.121075-1-prka@google.com> X-Mailer: git-send-email 2.48.1.711.g2feabab25a-goog Message-ID: <20250303205612.3955254-1-prka@google.com> To: ffmpeg-devel@ffmpeg.org Subject: [FFmpeg-devel] [PATCH v3] Mark C globals with small code model X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Pranav Kant via ffmpeg-devel Reply-To: FFmpeg development discussions and patches Cc: Pranav Kant Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: By default, all globals in C/C++ compiled by clang are allocated in non-large data sections. See [1] for background on code models. For PIC (Position independent code), this is fine as long as binary is small but as binary size increases, users maybe want to use medium/large code models (-mcmodel=medium) which moves data in to large sections. As data in these large sections cannot be accessed using PIC code anymore (as it may be too far away), compiler ends up using a different instruction sequence when building C/C++ code -- using GOT to access these globals (which can be relaxed by linker at link time if binary ends up being smaller). However, assembly files continue to access these globals defined in C/C++ files using older (and invalid instruction sequence). So, we mark all such globals with an attribute that forces them to be allocated in small sections allowing them to validly be accessed from the assembly code. This patch should not have any affect on builds that use small code model, which is the default mode. [1] https://eli.thegreenplace.net/2012/01/03/understanding-the-x64-code-models Signed-off-by: Pranav Kant --- libavcodec/ac3dsp.c | 2 ++ libavcodec/cabac.c | 2 ++ libavcodec/x86/constants.c | 8 ++++++++ libavutil/attributes.h | 6 ++++++ libavutil/attributes_internal.h | 16 ++++++++++++++++ 5 files changed, 34 insertions(+) diff --git a/libavcodec/ac3dsp.c b/libavcodec/ac3dsp.c index 730fa70fff..d16b6c24c3 100644 --- a/libavcodec/ac3dsp.c +++ b/libavcodec/ac3dsp.c @@ -25,6 +25,7 @@ #include "config.h" #include "libavutil/attributes.h" +#include "libavutil/attributes_internal.h" #include "libavutil/common.h" #include "libavutil/intmath.h" #include "libavutil/mem_internal.h" @@ -104,6 +105,7 @@ static void ac3_update_bap_counts_c(uint16_t mant_cnt[16], uint8_t *bap, mant_cnt[bap[len]]++; } +attribute_mcmodel_small DECLARE_ALIGNED(16, const uint16_t, ff_ac3_bap_bits)[16] = { 0, 0, 0, 3, 0, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 }; diff --git a/libavcodec/cabac.c b/libavcodec/cabac.c index 7d41cd2ae6..b8c6db29a2 100644 --- a/libavcodec/cabac.c +++ b/libavcodec/cabac.c @@ -24,11 +24,13 @@ * Context Adaptive Binary Arithmetic Coder. */ +#include "libavutil/attributes_internal.h" #include "libavutil/error.h" #include "libavutil/mem_internal.h" #include "cabac.h" +attribute_mcmodel_small DECLARE_ASM_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512 + 4*2*64 + 4*64 + 63] = { 9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, diff --git a/libavcodec/x86/constants.c b/libavcodec/x86/constants.c index bc7f2b17b8..347b7dd1d3 100644 --- a/libavcodec/x86/constants.c +++ b/libavcodec/x86/constants.c @@ -18,17 +18,21 @@ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +#include "libavutil/attributes_internal.h" #include "libavutil/mem_internal.h" #include "libavutil/x86/asm.h" // for xmm_reg #include "constants.h" +attribute_mcmodel_small DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1) = { 0x0001000100010001ULL, 0x0001000100010001ULL, 0x0001000100010001ULL, 0x0001000100010001ULL }; DECLARE_ALIGNED(32, const ymm_reg, ff_pw_2) = { 0x0002000200020002ULL, 0x0002000200020002ULL, 0x0002000200020002ULL, 0x0002000200020002ULL }; DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_3) = { 0x0003000300030003ULL, 0x0003000300030003ULL }; +attribute_mcmodel_small DECLARE_ASM_ALIGNED(32, const ymm_reg, ff_pw_4) = { 0x0004000400040004ULL, 0x0004000400040004ULL, 0x0004000400040004ULL, 0x0004000400040004ULL }; +attribute_mcmodel_small DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_5) = { 0x0005000500050005ULL, 0x0005000500050005ULL }; DECLARE_ALIGNED(16, const xmm_reg, ff_pw_8) = { 0x0008000800080008ULL, 0x0008000800080008ULL }; DECLARE_ASM_ALIGNED(16, const xmm_reg, ff_pw_9) = { 0x0009000900090009ULL, 0x0009000900090009ULL }; @@ -49,6 +53,7 @@ DECLARE_ALIGNED(32, const ymm_reg, ff_pw_256) = { 0x0100010001000100ULL, 0x010 DECLARE_ALIGNED(32, const ymm_reg, ff_pw_512) = { 0x0200020002000200ULL, 0x0200020002000200ULL, 0x0200020002000200ULL, 0x0200020002000200ULL }; DECLARE_ALIGNED(16, const xmm_reg, ff_pw_1019) = { 0x03FB03FB03FB03FBULL, 0x03FB03FB03FB03FBULL }; +attribute_mcmodel_small DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1023) = { 0x03ff03ff03ff03ffULL, 0x03ff03ff03ff03ffULL, 0x03ff03ff03ff03ffULL, 0x03ff03ff03ff03ffULL}; DECLARE_ALIGNED(32, const ymm_reg, ff_pw_1024) = { 0x0400040004000400ULL, 0x0400040004000400ULL, @@ -66,13 +71,16 @@ DECLARE_ALIGNED(32, const ymm_reg, ff_pw_m1) = { 0xFFFFFFFFFFFFFFFFULL, 0xFFF DECLARE_ALIGNED(32, const ymm_reg, ff_pb_0) = { 0x0000000000000000ULL, 0x0000000000000000ULL, 0x0000000000000000ULL, 0x0000000000000000ULL }; +attribute_mcmodel_small DECLARE_ALIGNED(32, const ymm_reg, ff_pb_1) = { 0x0101010101010101ULL, 0x0101010101010101ULL, 0x0101010101010101ULL, 0x0101010101010101ULL }; DECLARE_ALIGNED(32, const ymm_reg, ff_pb_2) = { 0x0202020202020202ULL, 0x0202020202020202ULL, 0x0202020202020202ULL, 0x0202020202020202ULL }; +attribute_mcmodel_small DECLARE_ALIGNED(32, const ymm_reg, ff_pb_3) = { 0x0303030303030303ULL, 0x0303030303030303ULL, 0x0303030303030303ULL, 0x0303030303030303ULL }; DECLARE_ALIGNED(32, const xmm_reg, ff_pb_15) = { 0x0F0F0F0F0F0F0F0FULL, 0x0F0F0F0F0F0F0F0FULL }; +attribute_mcmodel_small DECLARE_ALIGNED(32, const ymm_reg, ff_pb_80) = { 0x8080808080808080ULL, 0x8080808080808080ULL, 0x8080808080808080ULL, 0x8080808080808080ULL }; DECLARE_ALIGNED(32, const ymm_reg, ff_pb_FE) = { 0xFEFEFEFEFEFEFEFEULL, 0xFEFEFEFEFEFEFEFEULL, diff --git a/libavutil/attributes.h b/libavutil/attributes.h index 04c615c952..dfc35fa31e 100644 --- a/libavutil/attributes.h +++ b/libavutil/attributes.h @@ -40,6 +40,12 @@ # define AV_HAS_BUILTIN(x) 0 #endif +#ifdef __has_attribute +# define AV_HAS_ATTRIBUTE(x) __has_attribute(x) +#else +# define AV_HAS_ATTRIBUTE(x) 0 +#endif + #ifndef av_always_inline #if AV_GCC_VERSION_AT_LEAST(3,1) # define av_always_inline __attribute__((always_inline)) inline diff --git a/libavutil/attributes_internal.h b/libavutil/attributes_internal.h index 3df1ee6af3..87e490dd18 100644 --- a/libavutil/attributes_internal.h +++ b/libavutil/attributes_internal.h @@ -19,6 +19,7 @@ #ifndef AVUTIL_ATTRIBUTES_INTERNAL_H #define AVUTIL_ATTRIBUTES_INTERNAL_H +#include "config.h" #include "attributes.h" #if (AV_GCC_VERSION_AT_LEAST(4,0) || defined(__clang__)) && (defined(__ELF__) || defined(__MACH__)) @@ -31,4 +32,19 @@ # define FF_VISIBILITY_POP_HIDDEN #endif +/** + * Some globals defined in C files are used from hardcoded asm that assumes small + * code model (that is, accessing these globals without GOT). This is a problem + * when FFMpeg is built with medium code model (-mcmodel=medium) which allocates + * all globals in a data section that's unreachable with PC relative instructions + * (small code model instruction sequence). We mark all such globals with this + * attribute_mcmodel_small to ensure assembly accessible globals continue to be + * allocated in sections reachable from PC relative instructions. + */ +#if ARCH_X86_64 && defined(__ELF__) && AV_HAS_ATTRIBUTE(model) +# define attribute_mcmodel_small __attribute__(model("small")) +#else +# define attribute_mcmodel_small +#endif + #endif /* AVUTIL_ATTRIBUTES_INTERNAL_H */ -- 2.48.1.711.g2feabab25a-goog _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".