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![Ard Biesheuvel](/assets/img/avatar_default.png)
Commit3193c0836
("bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()") introduced a __no_fgcse macro that expands to a function scope __attribute__((optimize("-fno-gcse"))), to disable a GCC specific optimization that was causing trouble on x86 builds, and was not expected to have any positive effect in the first place. However, as the GCC manual documents, __attribute__((optimize)) is not for production use, and results in all other optimization options to be forgotten for the function in question. This can cause all kinds of trouble, but in one particular reported case, it causes -fno-asynchronous-unwind-tables to be disregarded, resulting in .eh_frame info to be emitted for the function. This reverts commit3193c0836
, and instead, it disables the -fgcse optimization for the entire source file, but only when building for X86 using GCC with CONFIG_BPF_JIT_ALWAYS_ON disabled. Note that the original commit states that CONFIG_RETPOLINE=n triggers the issue, whereas CONFIG_RETPOLINE=y performs better without the optimization, so it is kept disabled in both cases. Fixes:3193c0836f
("bpf: Disable GCC -fgcse optimization for ___bpf_prog_run()") Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/lkml/CAMuHMdUg0WJHEcq6to0-eODpXPOywLot6UD2=GFHpzoj_hCoBQ@mail.gmail.com/ Link: https://lore.kernel.org/bpf/20201028171506.15682-2-ardb@kernel.org
177 lines
5.8 KiB
C
177 lines
5.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_COMPILER_TYPES_H
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#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
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#endif
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/*
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* Common definitions for all gcc versions go here.
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*/
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#define GCC_VERSION (__GNUC__ * 10000 \
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+ __GNUC_MINOR__ * 100 \
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+ __GNUC_PATCHLEVEL__)
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/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
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#if GCC_VERSION < 40900
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# error Sorry, your version of GCC is too old - please use 4.9 or newer.
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#endif
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/* Optimization barrier */
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/* The "volatile" is due to gcc bugs */
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#define barrier() __asm__ __volatile__("": : :"memory")
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/*
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* This version is i.e. to prevent dead stores elimination on @ptr
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* where gcc and llvm may behave differently when otherwise using
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* normal barrier(): while gcc behavior gets along with a normal
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* barrier(), llvm needs an explicit input variable to be assumed
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* clobbered. The issue is as follows: while the inline asm might
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* access any memory it wants, the compiler could have fit all of
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* @ptr into memory registers instead, and since @ptr never escaped
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* from that, it proved that the inline asm wasn't touching any of
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* it. This version works well with both compilers, i.e. we're telling
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* the compiler that the inline asm absolutely may see the contents
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* of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
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*/
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#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
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/*
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* This macro obfuscates arithmetic on a variable address so that gcc
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* shouldn't recognize the original var, and make assumptions about it.
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*
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* This is needed because the C standard makes it undefined to do
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* pointer arithmetic on "objects" outside their boundaries and the
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* gcc optimizers assume this is the case. In particular they
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* assume such arithmetic does not wrap.
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*
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* A miscompilation has been observed because of this on PPC.
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* To work around it we hide the relationship of the pointer and the object
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* using this macro.
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*
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* Versions of the ppc64 compiler before 4.1 had a bug where use of
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* RELOC_HIDE could trash r30. The bug can be worked around by changing
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* the inline assembly constraint from =g to =r, in this particular
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* case either is valid.
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*/
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#define RELOC_HIDE(ptr, off) \
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({ \
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unsigned long __ptr; \
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__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
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(typeof(ptr)) (__ptr + (off)); \
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})
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#ifdef CONFIG_RETPOLINE
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#define __noretpoline __attribute__((__indirect_branch__("keep")))
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#endif
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#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
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#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
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#define __compiletime_warning(message) __attribute__((__warning__(message)))
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#define __compiletime_error(message) __attribute__((__error__(message)))
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#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
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#define __latent_entropy __attribute__((latent_entropy))
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#endif
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/*
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* calling noreturn functions, __builtin_unreachable() and __builtin_trap()
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* confuse the stack allocation in gcc, leading to overly large stack
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* frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
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*
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* Adding an empty inline assembly before it works around the problem
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*/
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#define barrier_before_unreachable() asm volatile("")
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/*
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* Mark a position in code as unreachable. This can be used to
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* suppress control flow warnings after asm blocks that transfer
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* control elsewhere.
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*/
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#define unreachable() \
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do { \
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annotate_unreachable(); \
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barrier_before_unreachable(); \
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__builtin_unreachable(); \
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} while (0)
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#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
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#define __randomize_layout __attribute__((randomize_layout))
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#define __no_randomize_layout __attribute__((no_randomize_layout))
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/* This anon struct can add padding, so only enable it under randstruct. */
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#define randomized_struct_fields_start struct {
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#define randomized_struct_fields_end } __randomize_layout;
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#endif
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/*
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* GCC 'asm goto' miscompiles certain code sequences:
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*
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* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
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*
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* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
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*
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* (asm goto is automatically volatile - the naming reflects this.)
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*/
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#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
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/*
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* sparse (__CHECKER__) pretends to be gcc, but can't do constant
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* folding in __builtin_bswap*() (yet), so don't set these for it.
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*/
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#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
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#define __HAVE_BUILTIN_BSWAP32__
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#define __HAVE_BUILTIN_BSWAP64__
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#define __HAVE_BUILTIN_BSWAP16__
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#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
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#if GCC_VERSION >= 70000
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#define KASAN_ABI_VERSION 5
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#elif GCC_VERSION >= 50000
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#define KASAN_ABI_VERSION 4
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#elif GCC_VERSION >= 40902
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#define KASAN_ABI_VERSION 3
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#endif
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#if __has_attribute(__no_sanitize_address__)
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#define __no_sanitize_address __attribute__((no_sanitize_address))
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#else
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#define __no_sanitize_address
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#endif
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#if defined(__SANITIZE_THREAD__) && __has_attribute(__no_sanitize_thread__)
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#define __no_sanitize_thread __attribute__((no_sanitize_thread))
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#else
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#define __no_sanitize_thread
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#endif
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#if __has_attribute(__no_sanitize_undefined__)
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#define __no_sanitize_undefined __attribute__((no_sanitize_undefined))
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#else
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#define __no_sanitize_undefined
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#endif
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#if GCC_VERSION >= 50100
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#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
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#endif
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/*
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* Turn individual warnings and errors on and off locally, depending
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* on version.
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*/
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#define __diag_GCC(version, severity, s) \
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__diag_GCC_ ## version(__diag_GCC_ ## severity s)
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/* Severity used in pragma directives */
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#define __diag_GCC_ignore ignored
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#define __diag_GCC_warn warning
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#define __diag_GCC_error error
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#define __diag_str1(s) #s
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#define __diag_str(s) __diag_str1(s)
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#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
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#if GCC_VERSION >= 80000
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#define __diag_GCC_8(s) __diag(s)
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#else
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#define __diag_GCC_8(s)
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#endif
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