[PATCH] uml: Use klibc setjmp/longjmp

This patch adds an implementation of setjmp and longjmp to UML, allowing
access to the inside of a jmpbuf without needing the access macros formerly
provided by libc.

The implementation is stolen from klibc.  I copy the relevant files into
arch/um.  I have another patch which avoids the copying, but requires klibc be
in the tree.

setjmp and longjmp users required some tweaking.  Includes of <setjmp.h> were
removed and includes of the UML longjmp.h were added where necessary.  There
are also replacements of siglongjmp with UML_LONGJMP which I somehow missed
earlier.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 56 insertions, 2 deletions

diff --git a/arch/um/sys-x86_64/Makefile b/arch/um/sys-x86_64/Makefile
index c19794d435d6..f41768b8e25e 100644
--- a/arch/um/sys-x86_64/Makefile
+++ b/arch/um/sys-x86_64/Makefile
@@ -5,8 +5,8 @@
 #
 
 obj-y = bugs.o delay.o fault.o ldt.o mem.o ptrace.o ptrace_user.o \
-        sigcontext.o signal.o syscalls.o syscall_table.o sysrq.o ksyms.o \
-        tls.o
+        setjmp.o sigcontext.o signal.o syscalls.o syscall_table.o sysrq.o \
+        ksyms.o tls.o
 
 obj-$(CONFIG_MODE_SKAS) += stub.o stub_segv.o
 obj-$(CONFIG_MODULES) += um_module.o
diff --git a/arch/um/sys-x86_64/setjmp.S b/arch/um/sys-x86_64/setjmp.S
new file mode 100644
index 000000000000..45f547b4043e
--- /dev/null
+++ b/arch/um/sys-x86_64/setjmp.S
@@ -0,0 +1,54 @@
+#
+# arch/x86_64/setjmp.S
+#
+# setjmp/longjmp for the x86-64 architecture
+#
+
+#
+# The jmp_buf is assumed to contain the following, in order:
+#       %rbx
+#       %rsp (post-return)
+#       %rbp
+#       %r12
+#       %r13
+#       %r14
+#       %r15
+#       <return address>
+#
+
+        .text
+        .align 4
+        .globl setjmp
+        .type setjmp, @function
+setjmp:
+        pop  %rsi                       # Return address, and adjust the stack
+        xorl %eax,%eax                  # Return value
+        movq %rbx,(%rdi)
+        movq %rsp,8(%rdi)               # Post-return %rsp!
+        push %rsi                       # Make the call/return stack happy
+        movq %rbp,16(%rdi)
+        movq %r12,24(%rdi)
+        movq %r13,32(%rdi)
+        movq %r14,40(%rdi)
+        movq %r15,48(%rdi)
+        movq %rsi,56(%rdi)              # Return address
+        ret
+
+        .size setjmp,.-setjmp
+
+        .text
+        .align 4
+        .globl longjmp
+        .type longjmp, @function
+longjmp:
+        movl %esi,%eax                  # Return value (int)
+        movq (%rdi),%rbx
+        movq 8(%rdi),%rsp
+        movq 16(%rdi),%rbp
+        movq 24(%rdi),%r12
+        movq 32(%rdi),%r13
+        movq 40(%rdi),%r14
+        movq 48(%rdi),%r15
+        jmp *56(%rdi)
+
+        .size longjmp,.-longjmp