x86: Mark error_entry as forbidden to kprobes From: Prasanna S.P. This patch moves the entry.S:error_entry to .kprobes.text section, since code marked unsafe for kprobes jumps directly to entry.S::error_entry, that must be marked unsafe as well. This patch also moves all the ".previous.text" asm directives to ".previous" for kprobes section. AK: Following a similar i386 patch from Chuck Ebbert AK: Also merged Jeremy's fix in. +from: Jeremy Fitzhardinge KPROBE_ENTRY does a .section .kprobes.text, and expects its users to do a .previous at the end of the function. Unfortunately, if any code within the function switches sections, for example .fixup, then the .previous ends up putting all subsequent code into .fixup. Worse, any subsequent .fixup code gets intermingled with the code its supposed to be fixing (which is also in .fixup). It's surprising this didn't cause more havok. The fix is to use .pushsection/.popsection, so this stuff nests properly. A further cleanup would be to get rid of all .section/.previous pairs, since they're inherently fragile. Signed-off-by: Andi Kleen arch/i386/kernel/entry.S | 8 ++++---- arch/x86_64/kernel/entry.S | 13 +++++++------ include/linux/linkage.h | 6 +++++- 3 files changed, 16 insertions(+), 11 deletions(-) Index: linux/arch/x86_64/kernel/entry.S =================================================================== --- linux.orig/arch/x86_64/kernel/entry.S +++ linux/arch/x86_64/kernel/entry.S @@ -819,7 +819,7 @@ paranoid_schedule\trace: * Exception entry point. This expects an error code/orig_rax on the stack * and the exception handler in %rax. */ -ENTRY(error_entry) +KPROBE_ENTRY(error_entry) _frame RDI /* rdi slot contains rax, oldrax contains error code */ cld @@ -904,6 +904,7 @@ error_kernelspace: je error_swapgs jmp error_sti END(error_entry) + .popsection /* Reload gs selector with exception handling */ /* edi: new selector */ @@ -1023,7 +1024,7 @@ ENDPROC(execve) KPROBE_ENTRY(page_fault) errorentry do_page_fault END(page_fault) - .previous .text + .popsection ENTRY(coprocessor_error) zeroentry do_coprocessor_error @@ -1045,7 +1046,7 @@ KPROBE_ENTRY(debug) paranoidentry do_debug, DEBUG_STACK paranoidexit END(debug) - .previous .text + .popsection /* runs on exception stack */ KPROBE_ENTRY(nmi) @@ -1060,7 +1061,7 @@ KPROBE_ENTRY(nmi) CFI_ENDPROC #endif END(nmi) - .previous .text + .popsection KPROBE_ENTRY(int3) INTR_FRAME @@ -1070,7 +1071,7 @@ KPROBE_ENTRY(int3) jmp paranoid_exit1 CFI_ENDPROC END(int3) - .previous .text + .popsection ENTRY(overflow) zeroentry do_overflow @@ -1119,7 +1120,7 @@ END(stack_segment) KPROBE_ENTRY(general_protection) errorentry do_general_protection END(general_protection) - .previous .text + .popsection ENTRY(alignment_check) errorentry do_alignment_check Index: linux/arch/i386/kernel/entry.S =================================================================== --- linux.orig/arch/i386/kernel/entry.S +++ linux/arch/i386/kernel/entry.S @@ -639,7 +639,7 @@ error_code: call *%edi jmp ret_from_exception CFI_ENDPROC -.previous +KPROBE_END(page_fault) ENTRY(coprocessor_error) RING0_INT_FRAME @@ -715,7 +715,7 @@ debug_stack_correct: call do_debug jmp ret_from_exception CFI_ENDPROC -.previous +KPROBE_END(debug) /* * NMI is doubly nasty. It can happen _while_ we're handling @@ -812,7 +812,7 @@ KPROBE_ENTRY(int3) call do_int3 jmp ret_from_exception CFI_ENDPROC -.previous +KPROBE_END(int3) ENTRY(overflow) RING0_INT_FRAME @@ -877,7 +877,7 @@ KPROBE_ENTRY(general_protection) CFI_ADJUST_CFA_OFFSET 4 jmp error_code CFI_ENDPROC -.previous +KPROBE_END(general_protection) ENTRY(alignment_check) RING0_EC_FRAME Index: linux/include/linux/linkage.h =================================================================== --- linux.orig/include/linux/linkage.h +++ linux/include/linux/linkage.h @@ -35,9 +35,13 @@ #endif #define KPROBE_ENTRY(name) \ - .section .kprobes.text, "ax"; \ + .pushsection .kprobes.text, "ax"; \ ENTRY(name) +#define KPROBE_END(name) \ + END(name); \ + .popsection + #ifndef END #define END(name) \ .size name, .-name