linux-kernel - [PATCH 9/9] um: switch ptrace FP register access to nolibc

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Message-ID: <20250915071115.1429196-10-benjamin@sipsolutions.net>
Date: Mon, 15 Sep 2025 09:11:15 +0200
From: Benjamin Berg <benjamin@...solutions.net>
To: linux-um@...ts.infradead.org,
	Willy Tarreau <w@....eu>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	linux-kselftest@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Tiwei Bie <tiwei.btw@...group.com>,
	Benjamin Berg <benjamin.berg@...el.com>
Subject: [PATCH 9/9] um: switch ptrace FP register access to nolibc

From: Benjamin Berg <benjamin.berg@...el.com>

The registers.c file only contain the routines for floating point
register access in ptrace mode and initial size detection. The file can
be moved over to nolibc by replacing the ptrace libc call with a simple
wrapper that does a direct syscall.

Signed-off-by: Benjamin Berg <benjamin.berg@...el.com>
---
 arch/x86/um/os-Linux/Makefile    |  5 ++++-
 arch/x86/um/os-Linux/registers.c | 22 ++++++++--------------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/arch/x86/um/os-Linux/Makefile b/arch/x86/um/os-Linux/Makefile
index 77a308aaa5ec..d37320430822 100644
--- a/arch/x86/um/os-Linux/Makefile
+++ b/arch/x86/um/os-Linux/Makefile
@@ -3,10 +3,13 @@
 # Licensed under the GPL
 #
 
-obj-y = registers.o mcontext.o
+obj-y = mcontext.o
 
 obj-$(CONFIG_X86_32) += tls.o
 
 USER_OBJS := $(obj-y)
 
+obj-y += registers.o
+NOLIBC_OBJS := registers.o
+
 include $(srctree)/arch/um/scripts/Makefile.rules
diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
index eb1cdadc8a61..55bce0d3f5d2 100644
--- a/arch/x86/um/os-Linux/registers.c
+++ b/arch/x86/um/os-Linux/registers.c
@@ -6,18 +6,20 @@
 
 #include <errno.h>
 #include <stdlib.h>
-#include <sys/ptrace.h>
+#include <linux/ptrace.h>
 #ifdef __i386__
 #include <sys/user.h>
 #endif
 #include <longjmp.h>
 #include <sysdep/ptrace_user.h>
-#include <sys/uio.h>
+#include <linux/uio.h>
 #include <asm/sigcontext.h>
 #include <linux/elf.h>
 #include <registers.h>
 #include <sys/mman.h>
 
+#define my_ptrace(...) my_syscall4(__NR_ptrace, __VA_ARGS__)
+
 static unsigned long ptrace_regset;
 unsigned long host_fp_size;
 
@@ -28,9 +30,7 @@ int get_fp_registers(int pid, unsigned long *regs)
 		.iov_len = host_fp_size,
 	};
 
-	if (ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov) < 0)
-		return -errno;
-	return 0;
+	return my_ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
 }
 
 int put_fp_registers(int pid, unsigned long *regs)
@@ -40,9 +40,7 @@ int put_fp_registers(int pid, unsigned long *regs)
 		.iov_len = host_fp_size,
 	};
 
-	if (ptrace(PTRACE_SETREGSET, pid, ptrace_regset, &iov) < 0)
-		return -errno;
-	return 0;
+	return my_ptrace(PTRACE_SETREGSET, pid, ptrace_regset, &iov);
 }
 
 int arch_init_registers(int pid)
@@ -60,9 +58,7 @@ int arch_init_registers(int pid)
 
 	/* GDB has x86_xsave_length, which uses x86_cpuid_count */
 	ptrace_regset = NT_X86_XSTATE;
-	ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
-	if (ret)
-		ret = -errno;
+	ret = my_ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
 
 	if (ret == -ENODEV) {
 #ifdef CONFIG_X86_32
@@ -71,9 +67,7 @@ int arch_init_registers(int pid)
 		ptrace_regset = NT_PRFPREG;
 #endif
 		iov.iov_len = 2 * 1024 * 1024;
-		ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
-		if (ret)
-			ret = -errno;
+		ret = my_ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
 	}
 
 	munmap(iov.iov_base, 2 * 1024 * 1024);
-- 
2.51.0