From: David Woodhouse <dwmw2@infradead.org>
To: Andi Kleen <ak@linux.intel.com>,
"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
"hongjiu.lu@intel.com" <hongjiu.lu@intel.com>,
"Tsimbalist, Igor V" <igor.v.tsimbalist@intel.com>
Cc: Paul Turner <pjt@google.com>, LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
tglx@linutronix.de, Kees Cook <keescook@google.com>,
Rik van Riel <riel@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@amacapital.net>,
Jiri Kosina <jikos@kernel.org>,
gnomes@lxorguk.ukuu.org.uk
Subject: Re: [RFC PATCH 13/12] Retpoline vs. CONFIG_TRIM_UNUSED_SYMBOLS
Date: Sun, 07 Jan 2018 08:03:11 +0000 [thread overview]
Message-ID: <1515312191.29312.299.camel@infradead.org> (raw)
In-Reply-To: <1515283824.29312.288.camel@infradead.org>
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On Sun, 2018-01-07 at 00:10 +0000, David Woodhouse wrote:
> Arjan pointed out that CONFIG_TRIM_UNUSED_SYMBOLS *really* doesn't like
> the dot in the symbols that GCC uses for the thunks.
>
> This seems to work, although my eyes are bleeding just a little bit.
>
> Given this, and the hack we already needed for MODVERSIONS, I wonder if
> a better approach might be to export the thunks using underscores in
> place of the dots, which is a relatively simple abuse of
> __EXPORT_SYMBOL(__x86_indirect_thunk_foo,__x86.indirect_thunk.foo,),
> and then have a hack either when generating or loading modules to do
> the same replacement.
Alternatively, and much simpler... HJ (or Igor), please can we change
the GCC patches so that the __x86.indirect_thunk.rxx symbols don't have
those awful dots in them? They are causing *lots* of pain.
Or we could build *modules* with the inline thunk and lose the ability
to ALTERNATIVE it away, I suppose.
> diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
> index ccb117a4588b..64d7a45ea954 100644
> --- a/arch/x86/lib/retpoline.S
> +++ b/arch/x86/lib/retpoline.S
> @@ -8,7 +8,13 @@
> #include
> #include
>
> -.macro THUNK reg
> +#ifdef CONFIG_TRIM_UNUSED_KSYMS
> +#define EXPORT_REG(reg) __is_defined(__KSYM___x86_indirect_thunk_ ## reg)
> +#else
> +#define EXPORT_REG(reg) 1
> +#endif
> +
> +.macro THUNK reg export
> .section .text.__x86.indirect_thunk.\reg
>
> ENTRY(__x86.indirect_thunk.\reg)
> @@ -16,15 +22,33 @@ ENTRY(__x86.indirect_thunk.\reg)
> NOSPEC_JMP %\reg
> CFI_ENDPROC
> ENDPROC(__x86.indirect_thunk.\reg)
> -EXPORT_SYMBOL(__x86.indirect_thunk.\reg)
> +
> +.if \export
> + EXPORT_SYMBOL_FORCE(__x86.indirect_thunk.\reg)
> +.endif
> .endm
>
> -#ifdef CONFIG_64BIT
> -.irp reg rax rbx rcx rdx rsi rdi rbp r8 r9 r10 r11 r12 r13 r14 r15
> - THUNK \reg
> -.endr
> +#ifdef __KSYM_DEPS__
> +#define GENERATE_THUNK(reg) EXPORT_SYMBOL(__x86.indirect_thunk. ## reg)
> #else
> -.irp reg eax ebx ecx edx esi edi ebp
> - THUNK \reg
> -.endr
> +#define GENERATE_THUNK(reg) THUNK reg EXPORT_REG(reg)
> +#endif
> +
> +GENERATE_THUNK(_ASM_AX)
> +GENERATE_THUNK(_ASM_BX)
> +GENERATE_THUNK(_ASM_CX)
> +GENERATE_THUNK(_ASM_DX)
> +GENERATE_THUNK(_ASM_SI)
> +GENERATE_THUNK(_ASM_DI)
> +GENERATE_THUNK(_ASM_BP)
> +GENERATE_THUNK(_ASM_SP)
> +#ifdef CONFIG_64BIT
> +GENERATE_THUNK(r8)
> +GENERATE_THUNK(r9)
> +GENERATE_THUNK(r10)
> +GENERATE_THUNK(r11)
> +GENERATE_THUNK(r12)
> +GENERATE_THUNK(r13)
> +GENERATE_THUNK(r14)
> +GENERATE_THUNK(r15)
> #endif
> diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
> index 719db1968d81..b13bb65e2530 100644
> --- a/include/asm-generic/export.h
> +++ b/include/asm-generic/export.h
> @@ -63,33 +63,33 @@ KSYM(__kcrctab_\name):
>
> #if defined(__KSYM_DEPS__)
>
> -#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
> +#define __EXPORT_SYMBOL(sym, val, sec, force) === __KSYM_##sym ===
>
> #elif defined(CONFIG_TRIM_UNUSED_KSYMS)
>
> #include
> #include
>
> -#define __EXPORT_SYMBOL(sym, val, sec) \
> - __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
> +#define __EXPORT_SYMBOL(sym, val, sec, force) \
> + __cond_export_sym(sym, val, sec, __or(force, __is_defined(__KSYM_##sym)))
> #define __cond_export_sym(sym, val, sec, conf) \
> ___cond_export_sym(sym, val, sec, conf)
> #define ___cond_export_sym(sym, val, sec, enabled) \
> __cond_export_sym_##enabled(sym, val, sec)
> #define __cond_export_sym_1(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
> #define __cond_export_sym_0(sym, val, sec) /* nothing */
> -
> #else
> -#define __EXPORT_SYMBOL(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
> +#define __EXPORT_SYMBOL(sym, val, sec, force) ___EXPORT_SYMBOL sym, val, sec
> #endif
>
> #define EXPORT_SYMBOL(name) \
> - __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)),)
> + __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), , 0)
> #define EXPORT_SYMBOL_GPL(name) \
> - __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), _gpl)
> + __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), _gpl, 0)
> #define EXPORT_DATA_SYMBOL(name) \
> - __EXPORT_SYMBOL(name, KSYM(name),)
> + __EXPORT_SYMBOL(name, KSYM(name), , 0)
> #define EXPORT_DATA_SYMBOL_GPL(name) \
> - __EXPORT_SYMBOL(name, KSYM(name),_gpl)
> -
> + __EXPORT_SYMBOL(name, KSYM(name), _gpl, 0)
> +#define EXPORT_SYMBOL_FORCE(name) \
> + __EXPORT_SYMBOL(name, KSYM(name), , 1)
> #endif
> diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
> index 513da1a4a2da..991cd136291b 100755
> --- a/scripts/adjust_autoksyms.sh
> +++ b/scripts/adjust_autoksyms.sh
> @@ -60,7 +60,7 @@ cat > "$new_ksyms_file" << EOT
>
> EOT
> [ "$(ls -A "$MODVERDIR")" ] &&
> -sed -ns -e '3{s/ /\n/g;/^$/!p;}' "$MODVERDIR"/*.mod | sort -u |
> +sed -ns -e '3{s/ /\n/g;/^$/!p;}' "$MODVERDIR"/*.mod | sort -u | tr . _ |
> while read sym; do
> if [ -n "$CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX" ]; then
> sym="${sym#_}"
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next prev parent reply other threads:[~2018-01-07 8:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-06 11:49 [PATCH v5 00/12] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-06 11:49 ` [PATCH v5 01/12] x86/spectre: Add X86_BUG_SPECTRE_V[12] David Woodhouse
2018-01-06 21:05 ` [tip:x86/pti] x86/cpufeatures: " tip-bot for David Woodhouse
2018-01-06 11:49 ` [PATCH v5 02/12] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-06 17:32 ` David Woodhouse
2018-01-06 18:05 ` [PATCH v5.1 " David Woodhouse
2018-01-06 18:35 ` [PATCH v5 " Eric Biggers
2018-01-06 19:17 ` David Woodhouse
2018-01-06 21:16 ` Andrew Cooper
2018-01-06 21:21 ` Woodhouse, David
2018-01-07 1:44 ` Tom Lendacky
2018-01-06 21:23 ` Thomas Gleixner
2018-01-06 21:34 ` Andrew Cooper
2018-01-06 21:49 ` Woodhouse, David
2018-01-06 11:49 ` [PATCH v5 03/12] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-06 11:49 ` [PATCH v5 04/12] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 05/12] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-06 18:13 ` Linus Torvalds
2018-01-06 19:53 ` Thomas Gleixner
2018-01-07 1:27 ` Linus Torvalds
2018-01-06 11:49 ` [PATCH v5 06/12] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 07/12] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 08/12] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 09/12] x86/retpoline/irq32: " David Woodhouse
2018-01-06 11:49 ` [PATCH v5 10/12] x86/retpoline: Add boot time option to disable retpoline David Woodhouse
2018-01-06 11:49 ` [PATCH v5 11/12] x86/retpoline: Exclude objtool with retpoline David Woodhouse
2018-01-06 11:49 ` [PATCH v5 12/12] retpoline/modpost: Quieten MODVERSION retpoline build David Woodhouse
2018-01-07 0:10 ` [RFC PATCH 13/12] Retpoline vs. CONFIG_TRIM_UNUSED_SYMBOLS David Woodhouse
2018-01-07 8:03 ` David Woodhouse [this message]
2018-01-07 15:09 ` Lu, Hongjiu
2018-01-07 17:32 ` David Woodhouse
2018-01-07 17:57 ` Lu, Hongjiu
2018-01-07 18:18 ` Thomas Gleixner
2018-01-07 18:32 ` Lu, Hongjiu
2018-01-07 20:57 ` David Woodhouse
2018-01-07 22:16 ` David Woodhouse
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