| From 9e809d15d6b692fa061d74be7aaab1c79f6784b8 Mon Sep 17 00:00:00 2001 |
| From: Dominik Brodowski <linux@dominikbrodowski.net> |
| Date: Wed, 14 Feb 2018 18:59:23 +0100 |
| Subject: x86/entry: Reduce the code footprint of the 'idtentry' macro |
| |
| From: Dominik Brodowski <linux@dominikbrodowski.net> |
| |
| commit 9e809d15d6b692fa061d74be7aaab1c79f6784b8 upstream. |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/entry/calling.h | 11 ++++++++++- |
| arch/x86/entry/entry_64.S | 18 ++++++++---------- |
| 2 files changed, 18 insertions(+), 11 deletions(-) |
| |
| --- a/arch/x86/entry/calling.h |
| +++ b/arch/x86/entry/calling.h |
| @@ -97,7 +97,7 @@ For 32-bit we have the following convent |
| |
| #define SIZEOF_PTREGS 21*8 |
| |
| -.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax |
| +.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 |
| /* |
| * Push registers and sanitize registers of values that a |
| * speculation attack might otherwise want to exploit. The |
| @@ -105,8 +105,14 @@ For 32-bit we have the following convent |
| * could be put to use in a speculative execution gadget. |
| * Interleave XOR with PUSH for better uop scheduling: |
| */ |
| + .if \save_ret |
| + pushq %rsi /* pt_regs->si */ |
| + movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */ |
| + movq %rdi, 8(%rsp) /* pt_regs->di (overwriting original return address) */ |
| + .else |
| pushq %rdi /* pt_regs->di */ |
| pushq %rsi /* pt_regs->si */ |
| + .endif |
| pushq \rdx /* pt_regs->dx */ |
| pushq %rcx /* pt_regs->cx */ |
| pushq \rax /* pt_regs->ax */ |
| @@ -131,6 +137,9 @@ For 32-bit we have the following convent |
| pushq %r15 /* pt_regs->r15 */ |
| xorq %r15, %r15 /* nospec r15*/ |
| UNWIND_HINT_REGS |
| + .if \save_ret |
| + pushq %rsi /* return address on top of stack */ |
| + .endif |
| .endm |
| |
| .macro POP_REGS pop_rdi=1 skip_r11rcx=0 |
| --- a/arch/x86/entry/entry_64.S |
| +++ b/arch/x86/entry/entry_64.S |
| @@ -867,12 +867,8 @@ ENTRY(\sym) |
| pushq $-1 /* ORIG_RAX: no syscall to restart */ |
| .endif |
| |
| - /* Save all registers in pt_regs */ |
| - PUSH_AND_CLEAR_REGS |
| - ENCODE_FRAME_POINTER |
| - |
| .if \paranoid < 2 |
| - testb $3, CS(%rsp) /* If coming from userspace, switch stacks */ |
| + testb $3, CS-ORIG_RAX(%rsp) /* If coming from userspace, switch stacks */ |
| jnz .Lfrom_usermode_switch_stack_\@ |
| .endif |
| |
| @@ -1117,13 +1113,15 @@ idtentry machine_check do_mce has_err |
| #endif |
| |
| /* |
| - * Switch gs if needed. |
| + * Save all registers in pt_regs, and switch gs if needed. |
| * Use slow, but surefire "are we in kernel?" check. |
| * Return: ebx=0: need swapgs on exit, ebx=1: otherwise |
| */ |
| ENTRY(paranoid_entry) |
| UNWIND_HINT_FUNC |
| cld |
| + PUSH_AND_CLEAR_REGS save_ret=1 |
| + ENCODE_FRAME_POINTER 8 |
| movl $1, %ebx |
| movl $MSR_GS_BASE, %ecx |
| rdmsr |
| @@ -1168,12 +1166,14 @@ ENTRY(paranoid_exit) |
| END(paranoid_exit) |
| |
| /* |
| - * Switch gs if needed. |
| + * Save all registers in pt_regs, and switch GS if needed. |
| * Return: EBX=0: came from user mode; EBX=1: otherwise |
| */ |
| ENTRY(error_entry) |
| - UNWIND_HINT_REGS offset=8 |
| + UNWIND_HINT_FUNC |
| cld |
| + PUSH_AND_CLEAR_REGS save_ret=1 |
| + ENCODE_FRAME_POINTER 8 |
| testb $3, CS+8(%rsp) |
| jz .Lerror_kernelspace |
| |
| @@ -1564,8 +1564,6 @@ end_repeat_nmi: |
| * frame to point back to repeat_nmi. |
| */ |
| pushq $-1 /* ORIG_RAX: no syscall to restart */ |
| - PUSH_AND_CLEAR_REGS |
| - ENCODE_FRAME_POINTER |
| |
| /* |
| * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit |