diff mbox series

[03/12] tools/nolibc: move entrypoint specifics to compiler.h

Message ID 20240728-nolibc-llvm-v1-3-bc384269bc35@weissschuh.net (mailing list archive)
State New
Headers show
Series tools/nolibc: improve LLVM/clang support | expand

Commit Message

Thomas Weißschuh July 28, 2024, 10:09 a.m. UTC 
The specific attributes for the _start entrypoint are duplicated for
each architecture.
Deduplicate it into a dedicated #define into compiler.h.
This make the code shorter and will make it easier to adapt for clang
compatibility.

For clang compatibility, the epilogue will also need to be adapted, so
move that one, too.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/include/nolibc/arch-aarch64.h   | 4 ++--
 tools/include/nolibc/arch-arm.h       | 4 ++--
 tools/include/nolibc/arch-i386.h      | 4 ++--
 tools/include/nolibc/arch-loongarch.h | 4 ++--
 tools/include/nolibc/arch-mips.h      | 4 ++--
 tools/include/nolibc/arch-powerpc.h   | 4 ++--
 tools/include/nolibc/arch-riscv.h     | 4 ++--
 tools/include/nolibc/arch-s390.h      | 4 ++--
 tools/include/nolibc/arch-x86_64.h    | 4 ++--
 tools/include/nolibc/compiler.h       | 3 +++
 10 files changed, 21 insertions(+), 18 deletions(-)

Comments

Willy Tarreau Aug. 3, 2024, 9:22 a.m. UTC | #1 
Hi Thomas,

On Sun, Jul 28, 2024 at 12:09:57PM +0200, Thomas Weißschuh wrote:
> The specific attributes for the _start entrypoint are duplicated for
> each architecture.
> Deduplicate it into a dedicated #define into compiler.h.
> This make the code shorter and will make it easier to adapt for clang
> compatibility.
> 
> For clang compatibility, the epilogue will also need to be adapted, so
> move that one, too.

I'm fine with the general approach, however I think that if we start to
add specific attributes and macros like this, we should prefix them with
"nolibc" to make sure they won't collide with userland.

Thanks,
willy
Thomas Weißschuh Aug. 3, 2024, 6:26 p.m. UTC | #2 
Aug 3, 2024 11:22:23 Willy Tarreau <w@1wt.eu>:

> Hi Thomas,
>
> On Sun, Jul 28, 2024 at 12:09:57PM +0200, Thomas Weißschuh wrote:
>> The specific attributes for the _start entrypoint are duplicated for
>> each architecture.
>> Deduplicate it into a dedicated #define into compiler.h.
>> This make the code shorter and will make it easier to adapt for clang
>> compatibility.
>>
>> For clang compatibility, the epilogue will also need to be adapted, so
>> move that one, too.
>
> I'm fine with the general approach, however I think that if we start to
> add specific attributes and macros like this, we should prefix them with
> "nolibc" to make sure they won't collide with userland.

Ack.

FYI for v2 I intend to rename the macros to
__nolibc_naked, as I have a followup series that needs
them also for the non-entrypoint asm functions in
arch-x86_64.

> Thanks,
> willy
diff mbox series

Patch

diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index b23ac1f04035..d5b182115664 100644
--- a/tools/include/nolibc/arch-aarch64.h
+++ b/tools/include/nolibc/arch-aarch64.h
@@ -142,13 +142,13 @@ 
 })
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"mov x0, sp\n"          /* save stack pointer to x0, as arg1 of _start_c */
 		"and sp, x0, -16\n"     /* sp must be 16-byte aligned in the callee      */
 		"bl  _start_c\n"        /* transfer to c runtime                         */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 #endif /* _NOLIBC_ARCH_AARCH64_H */
diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h
index d1c19d973e55..8e8a681a0740 100644
--- a/tools/include/nolibc/arch-arm.h
+++ b/tools/include/nolibc/arch-arm.h
@@ -185,7 +185,7 @@ 
 })
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"mov r0, sp\n"          /* save stack pointer to %r0, as arg1 of _start_c */
@@ -193,7 +193,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"mov sp, ip\n"
 		"bl  _start_c\n"        /* transfer to c runtime                          */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_ARM_H */
diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h
index 28c26a00a762..a464e3ae17fd 100644
--- a/tools/include/nolibc/arch-i386.h
+++ b/tools/include/nolibc/arch-i386.h
@@ -162,7 +162,7 @@ 
  * 2) The deepest stack frame should be set to zero
  *
  */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"xor  %ebp, %ebp\n"       /* zero the stack frame                                */
@@ -174,7 +174,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"call _start_c\n"         /* transfer to c runtime                               */
 		"hlt\n"                   /* ensure it does not return                           */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_I386_H */
diff --git a/tools/include/nolibc/arch-loongarch.h b/tools/include/nolibc/arch-loongarch.h
index 3f8ef8f86c0f..b3edb10be4c7 100644
--- a/tools/include/nolibc/arch-loongarch.h
+++ b/tools/include/nolibc/arch-loongarch.h
@@ -149,14 +149,14 @@ 
 #endif
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"move          $a0, $sp\n"         /* save stack pointer to $a0, as arg1 of _start_c */
 		LONG_BSTRINS " $sp, $zero, 3, 0\n" /* $sp must be 16-byte aligned                    */
 		"bl            _start_c\n"         /* transfer to c runtime                          */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_LOONGARCH_H */
diff --git a/tools/include/nolibc/arch-mips.h b/tools/include/nolibc/arch-mips.h
index 62cc50ef3288..afa5adc8c76b 100644
--- a/tools/include/nolibc/arch-mips.h
+++ b/tools/include/nolibc/arch-mips.h
@@ -179,7 +179,7 @@ 
 })
 
 /* startup code, note that it's called __start on MIPS */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector __start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector __start(void)
 {
 	__asm__ volatile (
 		".set push\n"
@@ -198,7 +198,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		" nop\n"                 /* delayed slot                                   */
 		".set pop\n"
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_MIPS_H */
diff --git a/tools/include/nolibc/arch-powerpc.h b/tools/include/nolibc/arch-powerpc.h
index 41ebd394b90c..c0a2d08e4e51 100644
--- a/tools/include/nolibc/arch-powerpc.h
+++ b/tools/include/nolibc/arch-powerpc.h
@@ -184,7 +184,7 @@ 
 #endif /* !__powerpc64__ */
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 #ifdef __powerpc64__
 #if _CALL_ELF == 2
@@ -215,7 +215,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"bl     _start_c\n"     /* transfer to c runtime                         */
 	);
 #endif
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_POWERPC_H */
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h
index 1927c643c739..90da3b328f6f 100644
--- a/tools/include/nolibc/arch-riscv.h
+++ b/tools/include/nolibc/arch-riscv.h
@@ -140,7 +140,7 @@ 
 })
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		".option push\n"
@@ -151,7 +151,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"andi sp, a0, -16\n"      /* sp must be 16-byte aligned                    */
 		"call _start_c\n"         /* transfer to c runtime                         */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #endif /* _NOLIBC_ARCH_RISCV_H */
diff --git a/tools/include/nolibc/arch-s390.h b/tools/include/nolibc/arch-s390.h
index 5d60fd43f883..09123861a140 100644
--- a/tools/include/nolibc/arch-s390.h
+++ b/tools/include/nolibc/arch-s390.h
@@ -139,7 +139,7 @@ 
 })
 
 /* startup code */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"lgr	%r2, %r15\n"          /* save stack pointer to %r2, as arg1 of _start_c */
@@ -147,7 +147,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"xc	0(8,%r15), 0(%r15)\n" /* clear backchain                                */
 		"brasl	%r14, _start_c\n"     /* transfer to c runtime                          */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 struct s390_mmap_arg_struct {
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index 68609f421934..98cb693cc38c 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -161,7 +161,7 @@ 
  * 2) The deepest stack frame should be zero (the %rbp).
  *
  */
-void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
+void __attribute__((weak, noreturn)) __entrypoint __no_stack_protector _start(void)
 {
 	__asm__ volatile (
 		"xor  %ebp, %ebp\n"       /* zero the stack frame                            */
@@ -170,7 +170,7 @@  void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 		"call _start_c\n"         /* transfer to c runtime                           */
 		"hlt\n"                   /* ensure it does not return                       */
 	);
-	__builtin_unreachable();
+	__entrypoint_epilogue();
 }
 
 #define NOLIBC_ARCH_HAS_MEMMOVE
diff --git a/tools/include/nolibc/compiler.h b/tools/include/nolibc/compiler.h
index beddc3665d69..fe3701863634 100644
--- a/tools/include/nolibc/compiler.h
+++ b/tools/include/nolibc/compiler.h
@@ -6,6 +6,9 @@ 
 #ifndef _NOLIBC_COMPILER_H
 #define _NOLIBC_COMPILER_H
 
+#define __entrypoint __attribute__((optimize("Os", "omit-frame-pointer")))
+#define __entrypoint_epilogue() __builtin_unreachable()
+
 #if defined(__SSP__) || defined(__SSP_STRONG__) || defined(__SSP_ALL__) || defined(__SSP_EXPLICIT__)
 
 #define _NOLIBC_STACKPROTECTOR