summaryrefslogtreecommitdiff
path: root/arch/x86/ia32
diff options
context:
space:
mode:
authorIngo Molnar <mingo@kernel.org>2015-05-28 12:21:47 +0200
committerIngo Molnar <mingo@kernel.org>2015-06-02 07:57:48 +0200
commit131484c8da97ed600c18dd9d03b661e8ae052df6 (patch)
tree18293a131e8a40a9a339734259a74d33cbba1186 /arch/x86/ia32
parentcdeb6048940fa4bfb429e2f1cba0d28a11e20cd5 (diff)
downloadlwn-131484c8da97ed600c18dd9d03b661e8ae052df6.tar.gz
lwn-131484c8da97ed600c18dd9d03b661e8ae052df6.zip
x86/debug: Remove perpetually broken, unmaintainable dwarf annotations
So the dwarf2 annotations in low level assembly code have become an increasing hindrance: unreadable, messy macros mixed into some of the most security sensitive code paths of the Linux kernel. These debug info annotations don't even buy the upstream kernel anything: dwarf driven stack unwinding has caused problems in the past so it's out of tree, and the upstream kernel only uses the much more robust framepointers based stack unwinding method. In addition to that there's a steady, slow bitrot going on with these annotations, requiring frequent fixups. There's no tooling and no functionality upstream that keeps it correct. So burn down the sick forest, allowing new, healthier growth: 27 files changed, 350 insertions(+), 1101 deletions(-) Someone who has the willingness and time to do this properly can attempt to reintroduce dwarf debuginfo in x86 assembly code plus dwarf unwinding from first principles, with the following conditions: - it should be maximally readable, and maximally low-key to 'ordinary' code reading and maintenance. - find a build time method to insert dwarf annotations automatically in the most common cases, for pop/push instructions that manipulate the stack pointer. This could be done for example via a preprocessing step that just looks for common patterns - plus special annotations for the few cases where we want to depart from the default. We have hundreds of CFI annotations, so automating most of that makes sense. - it should come with build tooling checks that ensure that CFI annotations are sensible. We've seen such efforts from the framepointer side, and there's no reason it couldn't be done on the dwarf side. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frédéric Weisbecker <fweisbec@gmail.com Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jan Beulich <JBeulich@suse.com> 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> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/ia32')
-rw-r--r--arch/x86/ia32/ia32entry.S133
1 files changed, 32 insertions, 101 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 63450a596800..2be23c734db5 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -4,7 +4,6 @@
* Copyright 2000-2002 Andi Kleen, SuSE Labs.
*/
-#include <asm/dwarf2.h>
#include <asm/calling.h>
#include <asm/asm-offsets.h>
#include <asm/current.h>
@@ -60,17 +59,6 @@
movl %eax,%eax /* zero extension */
.endm
- .macro CFI_STARTPROC32 simple
- CFI_STARTPROC \simple
- CFI_UNDEFINED r8
- CFI_UNDEFINED r9
- CFI_UNDEFINED r10
- CFI_UNDEFINED r11
- CFI_UNDEFINED r12
- CFI_UNDEFINED r13
- CFI_UNDEFINED r14
- CFI_UNDEFINED r15
- .endm
#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret32)
@@ -102,11 +90,6 @@ ENDPROC(native_usergs_sysret32)
* with the int 0x80 path.
*/
ENTRY(ia32_sysenter_target)
- CFI_STARTPROC32 simple
- CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,0
- CFI_REGISTER rsp,rbp
-
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
@@ -121,25 +104,21 @@ ENTRY(ia32_sysenter_target)
movl %eax, %eax
movl ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d
- CFI_REGISTER rip,r10
/* Construct struct pt_regs on stack */
- pushq_cfi $__USER32_DS /* pt_regs->ss */
- pushq_cfi %rbp /* pt_regs->sp */
- CFI_REL_OFFSET rsp,0
- pushfq_cfi /* pt_regs->flags */
- pushq_cfi $__USER32_CS /* pt_regs->cs */
- pushq_cfi %r10 /* pt_regs->ip = thread_info->sysenter_return */
- CFI_REL_OFFSET rip,0
- pushq_cfi_reg rax /* pt_regs->orig_ax */
- pushq_cfi_reg rdi /* pt_regs->di */
- pushq_cfi_reg rsi /* pt_regs->si */
- pushq_cfi_reg rdx /* pt_regs->dx */
- pushq_cfi_reg rcx /* pt_regs->cx */
- pushq_cfi $-ENOSYS /* pt_regs->ax */
+ pushq $__USER32_DS /* pt_regs->ss */
+ pushq %rbp /* pt_regs->sp */
+ pushfq /* pt_regs->flags */
+ pushq $__USER32_CS /* pt_regs->cs */
+ pushq %r10 /* pt_regs->ip = thread_info->sysenter_return */
+ pushq %rax /* pt_regs->orig_ax */
+ pushq %rdi /* pt_regs->di */
+ pushq %rsi /* pt_regs->si */
+ pushq %rdx /* pt_regs->dx */
+ pushq %rcx /* pt_regs->cx */
+ pushq $-ENOSYS /* pt_regs->ax */
cld
sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
- CFI_ADJUST_CFA_OFFSET 10*8
/*
* no need to do an access_ok check here because rbp has been
@@ -161,8 +140,8 @@ sysenter_flags_fixed:
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
- CFI_REMEMBER_STATE
jnz sysenter_tracesys
+
sysenter_do_call:
/* 32bit syscall -> 64bit C ABI argument conversion */
movl %edi,%r8d /* arg5 */
@@ -193,14 +172,12 @@ sysexit_from_sys_call:
*/
andl $~TS_COMPAT,ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
movl RIP(%rsp),%ecx /* User %eip */
- CFI_REGISTER rip,rcx
RESTORE_RSI_RDI
xorl %edx,%edx /* avoid info leaks */
xorq %r8,%r8
xorq %r9,%r9
xorq %r10,%r10
movl EFLAGS(%rsp),%r11d /* User eflags */
- /*CFI_RESTORE rflags*/
TRACE_IRQS_ON
/*
@@ -231,8 +208,6 @@ sysexit_from_sys_call:
*/
USERGS_SYSRET32
- CFI_RESTORE_STATE
-
#ifdef CONFIG_AUDITSYSCALL
.macro auditsys_entry_common
movl %esi,%r8d /* 5th arg: 4th syscall arg */
@@ -282,8 +257,8 @@ sysexit_audit:
#endif
sysenter_fix_flags:
- pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
- popfq_cfi
+ pushq $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
+ popfq
jmp sysenter_flags_fixed
sysenter_tracesys:
@@ -298,7 +273,6 @@ sysenter_tracesys:
LOAD_ARGS32 /* reload args from stack in case ptrace changed it */
RESTORE_EXTRA_REGS
jmp sysenter_do_call
- CFI_ENDPROC
ENDPROC(ia32_sysenter_target)
/*
@@ -332,12 +306,6 @@ ENDPROC(ia32_sysenter_target)
* with the int 0x80 path.
*/
ENTRY(ia32_cstar_target)
- CFI_STARTPROC32 simple
- CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,0
- CFI_REGISTER rip,rcx
- /*CFI_REGISTER rflags,r11*/
-
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
@@ -345,7 +313,6 @@ ENTRY(ia32_cstar_target)
*/
SWAPGS_UNSAFE_STACK
movl %esp,%r8d
- CFI_REGISTER rsp,r8
movq PER_CPU_VAR(cpu_current_top_of_stack),%rsp
ENABLE_INTERRUPTS(CLBR_NONE)
@@ -353,22 +320,19 @@ ENTRY(ia32_cstar_target)
movl %eax,%eax
/* Construct struct pt_regs on stack */
- pushq_cfi $__USER32_DS /* pt_regs->ss */
- pushq_cfi %r8 /* pt_regs->sp */
- CFI_REL_OFFSET rsp,0
- pushq_cfi %r11 /* pt_regs->flags */
- pushq_cfi $__USER32_CS /* pt_regs->cs */
- pushq_cfi %rcx /* pt_regs->ip */
- CFI_REL_OFFSET rip,0
- pushq_cfi_reg rax /* pt_regs->orig_ax */
- pushq_cfi_reg rdi /* pt_regs->di */
- pushq_cfi_reg rsi /* pt_regs->si */
- pushq_cfi_reg rdx /* pt_regs->dx */
- pushq_cfi_reg rbp /* pt_regs->cx */
+ pushq $__USER32_DS /* pt_regs->ss */
+ pushq %r8 /* pt_regs->sp */
+ pushq %r11 /* pt_regs->flags */
+ pushq $__USER32_CS /* pt_regs->cs */
+ pushq %rcx /* pt_regs->ip */
+ pushq %rax /* pt_regs->orig_ax */
+ pushq %rdi /* pt_regs->di */
+ pushq %rsi /* pt_regs->si */
+ pushq %rdx /* pt_regs->dx */
+ pushq %rbp /* pt_regs->cx */
movl %ebp,%ecx
- pushq_cfi $-ENOSYS /* pt_regs->ax */
+ pushq $-ENOSYS /* pt_regs->ax */
sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
- CFI_ADJUST_CFA_OFFSET 10*8
/*
* no need to do an access_ok check here because r8 has been
@@ -380,8 +344,8 @@ ENTRY(ia32_cstar_target)
ASM_CLAC
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
- CFI_REMEMBER_STATE
jnz cstar_tracesys
+
cstar_do_call:
/* 32bit syscall -> 64bit C ABI argument conversion */
movl %edi,%r8d /* arg5 */
@@ -403,15 +367,12 @@ sysretl_from_sys_call:
andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
RESTORE_RSI_RDI_RDX
movl RIP(%rsp),%ecx
- CFI_REGISTER rip,rcx
movl EFLAGS(%rsp),%r11d
- /*CFI_REGISTER rflags,r11*/
xorq %r10,%r10
xorq %r9,%r9
xorq %r8,%r8
TRACE_IRQS_ON
movl RSP(%rsp),%esp
- CFI_RESTORE rsp
/*
* 64bit->32bit SYSRET restores eip from ecx,
* eflags from r11 (but RF and VM bits are forced to 0),
@@ -430,7 +391,6 @@ sysretl_from_sys_call:
#ifdef CONFIG_AUDITSYSCALL
cstar_auditsys:
- CFI_RESTORE_STATE
movl %r9d,R9(%rsp) /* register to be clobbered by call */
auditsys_entry_common
movl R9(%rsp),%r9d /* reload 6th syscall arg */
@@ -460,7 +420,6 @@ ia32_badarg:
ASM_CLAC
movq $-EFAULT,%rax
jmp ia32_sysret
- CFI_ENDPROC
/*
* Emulated IA32 system calls via int 0x80.
@@ -484,15 +443,6 @@ ia32_badarg:
*/
ENTRY(ia32_syscall)
- CFI_STARTPROC32 simple
- CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,5*8
- /*CFI_REL_OFFSET ss,4*8 */
- CFI_REL_OFFSET rsp,3*8
- /*CFI_REL_OFFSET rflags,2*8 */
- /*CFI_REL_OFFSET cs,1*8 */
- CFI_REL_OFFSET rip,0*8
-
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
@@ -506,15 +456,14 @@ ENTRY(ia32_syscall)
movl %eax,%eax
/* Construct struct pt_regs on stack (iret frame is already on stack) */
- pushq_cfi_reg rax /* pt_regs->orig_ax */
- pushq_cfi_reg rdi /* pt_regs->di */
- pushq_cfi_reg rsi /* pt_regs->si */
- pushq_cfi_reg rdx /* pt_regs->dx */
- pushq_cfi_reg rcx /* pt_regs->cx */
- pushq_cfi $-ENOSYS /* pt_regs->ax */
+ pushq %rax /* pt_regs->orig_ax */
+ pushq %rdi /* pt_regs->di */
+ pushq %rsi /* pt_regs->si */
+ pushq %rdx /* pt_regs->dx */
+ pushq %rcx /* pt_regs->cx */
+ pushq $-ENOSYS /* pt_regs->ax */
cld
sub $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
- CFI_ADJUST_CFA_OFFSET 10*8
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -544,7 +493,6 @@ ia32_tracesys:
LOAD_ARGS32 /* reload args from stack in case ptrace changed it */
RESTORE_EXTRA_REGS
jmp ia32_do_call
- CFI_ENDPROC
END(ia32_syscall)
.macro PTREGSCALL label, func
@@ -554,8 +502,6 @@ GLOBAL(\label)
jmp ia32_ptregs_common
.endm
- CFI_STARTPROC32
-
PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
PTREGSCALL stub32_sigreturn, sys32_sigreturn
PTREGSCALL stub32_fork, sys_fork
@@ -569,23 +515,8 @@ GLOBAL(stub32_clone)
ALIGN
ia32_ptregs_common:
- CFI_ENDPROC
- CFI_STARTPROC32 simple
- CFI_SIGNAL_FRAME
- CFI_DEF_CFA rsp,SIZEOF_PTREGS
- CFI_REL_OFFSET rax,RAX
- CFI_REL_OFFSET rcx,RCX
- CFI_REL_OFFSET rdx,RDX
- CFI_REL_OFFSET rsi,RSI
- CFI_REL_OFFSET rdi,RDI
- CFI_REL_OFFSET rip,RIP
-/* CFI_REL_OFFSET cs,CS*/
-/* CFI_REL_OFFSET rflags,EFLAGS*/
- CFI_REL_OFFSET rsp,RSP
-/* CFI_REL_OFFSET ss,SS*/
SAVE_EXTRA_REGS 8
call *%rax
RESTORE_EXTRA_REGS 8
ret
- CFI_ENDPROC
END(ia32_ptregs_common)