Messages in this thread Patch in this message | | | Date | Thu, 30 Apr 2020 14:46:30 -0500 | From | Josh Poimboeuf <> | Subject | Re: Remaining randconfig objtool warnings, linux-next-20200428 |
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On Thu, Apr 30, 2020 at 09:33:50AM -0500, Josh Poimboeuf wrote: > On Thu, Apr 30, 2020 at 03:41:56PM +0200, Arnd Bergmann wrote: > > On Thu, Apr 30, 2020 at 1:28 AM Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > > > > > On Wed, Apr 29, 2020 at 06:11:15PM -0500, Josh Poimboeuf wrote: > > > > > We can probably move those SYS_NI() instances to kernel/sys_ni.c, > > > > > which does not include the header, but it's still a bit ugly. I'll try > > > > > that tomorrow > > > > > unless you come up with a better suggestion first. > > > > > > > > Oh I guess arm32 doesn't have SYS_NI defined. All this syscall aliasing > > > > stuff is a total mystery to me. > > > > > > Another idea would be to split up syscalls.h into two files: one for > > > SYSCALL_* macros and one for sys_*() function prototypes. It sounds > > > like the latter aren't needed by most header files anyway. > > > > > > * Please note that these prototypes here are only provided for information > > > * purposes, for static analysis, and for linking from the syscall table. > > > * These functions should not be called elsewhere from kernel code. > > > > To me the main purpose of the header is to ensure the calling conventions > > are sane, so I'd definitely want to see the declarations included whenever > > a syscall is defined. I would also expect to see a warnig from sparse, or > > from gcc with "make W=1" when an extern function is defined with no > > prior declaration. > > Yup, makes sense. I think I've been getting confused by the syscall > wrappers. > > > How hard would it be to change objtool instead of changing the sources? > > It might be a little tricky, but I can look into it.
So there's an easy fix below, just define an x86-specific SYSCALL_ALIAS. It also requries moving the syscall alias macros to syscalls.h, but that's probably where they belong anyway.
But the objtool .cold parent alias function detection is a little smelly, so I might end up cleaning that up instead if I can figure out a good way to do it.
diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h index a84333adeef2..abe6e633f8dc 100644 --- a/arch/x86/include/asm/syscall_wrapper.h +++ b/arch/x86/include/asm/syscall_wrapper.h @@ -79,6 +79,8 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs); return __se_##name(__VA_ARGS__); \ } +#define SYSCALL_ALIAS(alias, name) __alias(name) typeof(name) alias + #define __COND_SYSCALL(abi, name) \ __weak long __##abi##_##name(const struct pt_regs *__unused) \ { \ diff --git a/include/linux/linkage.h b/include/linux/linkage.h index d796ec20d114..369c65d4386c 100644 --- a/include/linux/linkage.h +++ b/include/linux/linkage.h @@ -22,20 +22,6 @@ #define asmlinkage CPP_ASMLINKAGE #endif -#ifndef cond_syscall -#define cond_syscall(x) asm( \ - ".weak " __stringify(x) "\n\t" \ - ".set " __stringify(x) "," \ - __stringify(sys_ni_syscall)) -#endif - -#ifndef SYSCALL_ALIAS -#define SYSCALL_ALIAS(alias, name) asm( \ - ".globl " __stringify(alias) "\n\t" \ - ".set " __stringify(alias) "," \ - __stringify(name)) -#endif - #define __page_aligned_data __section(.data..page_aligned) __aligned(PAGE_SIZE) #define __page_aligned_bss __section(.bss..page_aligned) __aligned(PAGE_SIZE) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 1815065d52f3..dc93d7e595af 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -252,6 +252,20 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) #endif /* __SYSCALL_DEFINEx */ +#ifndef SYSCALL_ALIAS +#define SYSCALL_ALIAS(alias, name) asm( \ + ".globl " __stringify(alias) "\n\t" \ + ".set " __stringify(alias) "," \ + __stringify(name)) +#endif + +#ifndef cond_syscall +#define cond_syscall(x) asm( \ + ".weak " __stringify(x) "\n\t" \ + ".set " __stringify(x) "," \ + __stringify(sys_ni_syscall)) +#endif + /* * Called before coming back to user-mode. Returning to user-mode with an * address limit different than USER_DS can allow to overwrite kernel memory.
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