[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] x86/asm: Introduce a tailcall pseduo-op
commit 8720e7f3a482580cabddfb3126351da56a4c9690 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Fri Jun 30 16:11:40 2023 +0100 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Wed Jul 5 15:20:04 2023 +0100 x86/asm: Introduce a tailcall pseduo-op It was previously noted that CALL/BUG is a weird combination, but there is good reason to use this pattern. Introduce an explicit tailcall macro make it clearer in context. No functional change. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/x86/boot/x86_64.S | 6 ++---- xen/arch/x86/include/asm/asm-defns.h | 9 +++++++++ xen/arch/x86/x86_64/entry.S | 12 ++++-------- 3 files changed, 15 insertions(+), 12 deletions(-) diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S index 5d12937a0e..04bb62ae86 100644 --- a/xen/arch/x86/boot/x86_64.S +++ b/xen/arch/x86/boot/x86_64.S @@ -74,14 +74,12 @@ ENTRY(__high_start) .L_ap_cet_done: #endif /* CONFIG_XEN_SHSTK || CONFIG_XEN_IBT */ - call start_secondary - BUG /* start_secondary() shouldn't return. */ + tailcall start_secondary .L_bsp: /* Pass off the Multiboot info structure to C land (if applicable). */ mov multiboot_ptr(%rip),%edi - call __start_xen - BUG /* __start_xen() shouldn't return. */ + tailcall __start_xen .section .data.page_aligned, "aw", @progbits .align PAGE_SIZE, 0 diff --git a/xen/arch/x86/include/asm/asm-defns.h b/xen/arch/x86/include/asm/asm-defns.h index 8bd9007731..9a7073ced5 100644 --- a/xen/arch/x86/include/asm/asm-defns.h +++ b/xen/arch/x86/include/asm/asm-defns.h @@ -20,6 +20,15 @@ .byte 0x0f, 0x01, 0xdd .endm +/* + * Call a noreturn function. This could be JMP, but CALL results in a more + * helpful backtrace. BUG is to catch functions which do decide to return... + */ +.macro tailcall fn:req + call \fn + BUG /* Shouldn't return */ +.endm + .macro INDIRECT_BRANCH insn:req arg:req /* * Create an indirect branch. insn is one of call/jmp, arg is a single diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index 8b77d7113b..bca1500e2b 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -824,8 +824,7 @@ handle_exception_saved: DISPATCH(X86_EXC_CP, do_entry_CP) #undef DISPATCH - call do_unhandled_trap - BUG /* do_unhandled_trap() shouldn't return. */ + tailcall do_unhandled_trap .L_exn_dispatch_done: mov %r15, STACK_CPUINFO_FIELD(xen_cr3)(%r14) @@ -880,8 +879,7 @@ exception_with_ints_disabled: FATAL_exception_with_ints_disabled: xorl %esi,%esi movq %rsp,%rdi - call fatal_trap - BUG /* fatal_trap() shouldn't return. */ + tailcall fatal_trap ENTRY(divide_error) ENDBR64 @@ -989,8 +987,7 @@ ENTRY(double_fault) .Ldblf_cr3_okay: movq %rsp,%rdi - call do_double_fault - BUG /* do_double_fault() shouldn't return. */ + tailcall do_double_fault ENTRY(nmi) ENDBR64 @@ -1085,8 +1082,7 @@ handle_ist_exception: DISPATCH(X86_EXC_MC, do_machine_check) #undef DISPATCH - call do_unhandled_trap - BUG /* do_unhandled_trap() shouldn't return. */ + tailcall do_unhandled_trap .L_ist_dispatch_done: mov %r15, STACK_CPUINFO_FIELD(xen_cr3)(%r14) -- generated by git-patchbot for /home/xen/git/xen.git#master
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