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x86/entry: Reduce the code footprint of the 'idtentry' macro
Play a little trick in the generic PUSH_AND_CLEAR_REGS macro to insert the GP registers "above" the original return address. This allows us to (re-)insert the macro in error_entry() and paranoid_entry() and to remove it from the idtentry macro. This reduces the static footprint significantly: text data bss dec hex filename 24307 0 0 24307 5ef3 entry_64.o-orig 20987 0 0 20987 51fb entry_64.o Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20180214175924.23065-2-linux@dominikbrodowski.net [ Small tweaks to comments. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
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2 changed files with 18 additions and 11 deletions
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@ -97,7 +97,7 @@ For 32-bit we have the following conventions - kernel is built with
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#define SIZEOF_PTREGS 21*8
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#define SIZEOF_PTREGS 21*8
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.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax
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.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
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/*
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/*
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* Push registers and sanitize registers of values that a
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* Push registers and sanitize registers of values that a
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* speculation attack might otherwise want to exploit. The
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* speculation attack might otherwise want to exploit. The
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@ -105,8 +105,14 @@ For 32-bit we have the following conventions - kernel is built with
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* could be put to use in a speculative execution gadget.
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* could be put to use in a speculative execution gadget.
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* Interleave XOR with PUSH for better uop scheduling:
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* Interleave XOR with PUSH for better uop scheduling:
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*/
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*/
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.if \save_ret
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pushq %rsi /* pt_regs->si */
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movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */
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movq %rdi, 8(%rsp) /* pt_regs->di (overwriting original return address) */
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.else
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pushq %rdi /* pt_regs->di */
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pushq %rdi /* pt_regs->di */
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pushq %rsi /* pt_regs->si */
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pushq %rsi /* pt_regs->si */
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.endif
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pushq \rdx /* pt_regs->dx */
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pushq \rdx /* pt_regs->dx */
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pushq %rcx /* pt_regs->cx */
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pushq %rcx /* pt_regs->cx */
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pushq \rax /* pt_regs->ax */
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pushq \rax /* pt_regs->ax */
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@ -131,6 +137,9 @@ For 32-bit we have the following conventions - kernel is built with
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pushq %r15 /* pt_regs->r15 */
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pushq %r15 /* pt_regs->r15 */
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xorq %r15, %r15 /* nospec r15*/
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xorq %r15, %r15 /* nospec r15*/
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UNWIND_HINT_REGS
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UNWIND_HINT_REGS
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.if \save_ret
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pushq %rsi /* return address on top of stack */
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.endif
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.endm
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.endm
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.macro POP_REGS pop_rdi=1 skip_r11rcx=0
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.macro POP_REGS pop_rdi=1 skip_r11rcx=0
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@ -875,12 +875,8 @@ ENTRY(\sym)
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pushq $-1 /* ORIG_RAX: no syscall to restart */
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pushq $-1 /* ORIG_RAX: no syscall to restart */
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.endif
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.endif
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/* Save all registers in pt_regs */
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PUSH_AND_CLEAR_REGS
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ENCODE_FRAME_POINTER
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.if \paranoid < 2
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.if \paranoid < 2
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testb $3, CS(%rsp) /* If coming from userspace, switch stacks */
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testb $3, CS-ORIG_RAX(%rsp) /* If coming from userspace, switch stacks */
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jnz .Lfrom_usermode_switch_stack_\@
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jnz .Lfrom_usermode_switch_stack_\@
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.endif
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.endif
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@ -1130,13 +1126,15 @@ idtentry machine_check do_mce has_error_code=0 paranoid=1
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#endif
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#endif
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/*
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/*
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* Switch gs if needed.
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* Save all registers in pt_regs, and switch gs if needed.
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* Use slow, but surefire "are we in kernel?" check.
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* Use slow, but surefire "are we in kernel?" check.
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* Return: ebx=0: need swapgs on exit, ebx=1: otherwise
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* Return: ebx=0: need swapgs on exit, ebx=1: otherwise
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*/
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*/
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ENTRY(paranoid_entry)
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ENTRY(paranoid_entry)
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UNWIND_HINT_FUNC
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UNWIND_HINT_FUNC
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cld
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cld
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PUSH_AND_CLEAR_REGS save_ret=1
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ENCODE_FRAME_POINTER 8
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movl $1, %ebx
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movl $1, %ebx
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movl $MSR_GS_BASE, %ecx
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movl $MSR_GS_BASE, %ecx
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rdmsr
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rdmsr
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@ -1181,12 +1179,14 @@ ENTRY(paranoid_exit)
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END(paranoid_exit)
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END(paranoid_exit)
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/*
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/*
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* Switch gs if needed.
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* Save all registers in pt_regs, and switch GS if needed.
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* Return: EBX=0: came from user mode; EBX=1: otherwise
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* Return: EBX=0: came from user mode; EBX=1: otherwise
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*/
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*/
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ENTRY(error_entry)
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ENTRY(error_entry)
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UNWIND_HINT_REGS offset=8
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UNWIND_HINT_FUNC
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cld
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cld
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PUSH_AND_CLEAR_REGS save_ret=1
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ENCODE_FRAME_POINTER 8
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testb $3, CS+8(%rsp)
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testb $3, CS+8(%rsp)
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jz .Lerror_kernelspace
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jz .Lerror_kernelspace
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@ -1577,8 +1577,6 @@ end_repeat_nmi:
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* frame to point back to repeat_nmi.
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* frame to point back to repeat_nmi.
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*/
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*/
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pushq $-1 /* ORIG_RAX: no syscall to restart */
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pushq $-1 /* ORIG_RAX: no syscall to restart */
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PUSH_AND_CLEAR_REGS
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ENCODE_FRAME_POINTER
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/*
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/*
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* Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
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* Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
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