[PATCH nolibc 55/61] tools/nolibc: Remove .global _start from the entry point code

[PATCH nolibc 55/61] tools/nolibc: Remove .global _start from the entry point code

[Paul E. McKenney]

From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

Building with clang yields the following error:
```
  <inline asm>:3:1: error: _start changed binding to STB_GLOBAL
  .global _start
  ^
  1 error generated.
```
Make sure only specify one between `.global _start` and `.weak _start`.
Remove `.global _start`.

Cc: llvm@lists.linux.dev
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/include/nolibc/arch-aarch64.h | 1 -
 tools/include/nolibc/arch-arm.h     | 1 -
 tools/include/nolibc/arch-i386.h    | 1 -
 tools/include/nolibc/arch-mips.h    | 1 -
 tools/include/nolibc/arch-riscv.h   | 1 -
 tools/include/nolibc/arch-x86_64.h  | 1 -
 6 files changed, 6 deletions(-)

diff --git a/tools/include/nolibc/arch-aarch64.h b/tools/include/nolibc/arch-aarch64.h
index b68443f63980..f68baf8f395f 100644
--- a/tools/include/nolibc/arch-aarch64.h
+++ b/tools/include/nolibc/arch-aarch64.h
@@ -184,7 +184,6 @@ struct sys_stat_struct {
 /* startup code */
 __asm__ (".section .text\n"
     ".weak _start\n"
-    ".global _start\n"
     "_start:\n"
     "ldr x0, [sp]\n"              // argc (x0) was in the stack
     "add x1, sp, 8\n"             // argv (x1) = sp
diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h
index 55fd9439b2e2..f31be8e967d6 100644
--- a/tools/include/nolibc/arch-arm.h
+++ b/tools/include/nolibc/arch-arm.h
@@ -177,7 +177,6 @@ struct sys_stat_struct {
 /* startup code */
 __asm__ (".section .text\n"
     ".weak _start\n"
-    ".global _start\n"
     "_start:\n"
 #if defined(__THUMBEB__) || defined(__THUMBEL__)
     /* We enter here in 32-bit mode but if some previous functions were in
diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h
index 136d5739e456..10aada40680d 100644
--- a/tools/include/nolibc/arch-i386.h
+++ b/tools/include/nolibc/arch-i386.h
@@ -176,7 +176,6 @@ struct sys_stat_struct {
  */
 __asm__ (".section .text\n"
     ".weak _start\n"
-    ".global _start\n"
     "_start:\n"
     "pop %eax\n"                // argc   (first arg, %eax)
     "mov %esp, %ebx\n"          // argv[] (second arg, %ebx)
diff --git a/tools/include/nolibc/arch-mips.h b/tools/include/nolibc/arch-mips.h
index cd587e539d7d..5fc5b8029bff 100644
--- a/tools/include/nolibc/arch-mips.h
+++ b/tools/include/nolibc/arch-mips.h
@@ -192,7 +192,6 @@ struct sys_stat_struct {
 __asm__ (".section .text\n"
     ".weak __start\n"
     ".set nomips16\n"
-    ".global __start\n"
     ".set    noreorder\n"
     ".option pic0\n"
     ".ent __start\n"
diff --git a/tools/include/nolibc/arch-riscv.h b/tools/include/nolibc/arch-riscv.h
index 8ec4c05fa69b..95e2b7924925 100644
--- a/tools/include/nolibc/arch-riscv.h
+++ b/tools/include/nolibc/arch-riscv.h
@@ -185,7 +185,6 @@ struct sys_stat_struct {
 /* startup code */
 __asm__ (".section .text\n"
     ".weak _start\n"
-    ".global _start\n"
     "_start:\n"
     ".option push\n"
     ".option norelax\n"
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index 490530429ac9..0e1e9eb8545d 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -199,7 +199,6 @@ struct sys_stat_struct {
  */
 __asm__ (".section .text\n"
     ".weak _start\n"
-    ".global _start\n"
     "_start:\n"
     "pop %rdi\n"                // argc   (first arg, %rdi)
     "mov %rsp, %rsi\n"          // argv[] (second arg, %rsi)
-- 
2.31.1.189.g2e36527f23

[PATCH nolibc 56/61] tools/nolibc: i386: Implement syscall with 6 arguments

[Paul E. McKenney]

From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

On i386, the 6th argument of syscall goes in %ebp. However, both Clang
and GCC cannot use %ebp in the clobber list and in the "r" constraint
without using -fomit-frame-pointer. To make it always available for
any kind of compilation, the below workaround is implemented.

  1) Push the 6-th argument.
  2) Push %ebp.
  3) Load the 6-th argument from 4(%esp) to %ebp.
  4) Do the syscall (int $0x80).
  5) Pop %ebp (restore the old value of %ebp).
  6) Add %esp by 4 (undo the stack pointer).

Cc: x86@kernel.org
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/lkml/2e335ac54db44f1d8496583d97f9dab0@AcuMS.aculab.com
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/include/nolibc/arch-i386.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h
index 10aada40680d..d7e7212346e2 100644
--- a/tools/include/nolibc/arch-i386.h
+++ b/tools/include/nolibc/arch-i386.h
@@ -167,6 +167,29 @@ struct sys_stat_struct {
 	_ret;                                                                 \
 })
 
+#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)	\
+({								\
+	long _eax  = (long)(num);				\
+	long _arg6 = (long)(arg6); /* Always in memory */	\
+	__asm__ volatile (					\
+		"pushl	%[_arg6]\n\t"				\
+		"pushl	%%ebp\n\t"				\
+		"movl	4(%%esp),%%ebp\n\t"			\
+		"int	$0x80\n\t"				\
+		"popl	%%ebp\n\t"				\
+		"addl	$4,%%esp\n\t"				\
+		: "+a"(_eax)		/* %eax */		\
+		: "b"(arg1),		/* %ebx */		\
+		  "c"(arg2),		/* %ecx */		\
+		  "d"(arg3),		/* %edx */		\
+		  "S"(arg4),		/* %esi */		\
+		  "D"(arg5),		/* %edi */		\
+		  [_arg6]"m"(_arg6)	/* memory */		\
+		: "memory", "cc"				\
+	);							\
+	_eax;							\
+})
+
 /* startup code */
 /*
  * i386 System V ABI mandates:
-- 
2.31.1.189.g2e36527f23