Changeset a7220de in mainline for kernel/arch/amd64/src/asm.S

Timestamp:

2010-07-14T12:15:10Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

c8cd9a8

Parents:

0d1e976

Message:

Rewrite syscall_entry() to use the istate structure and save all GPRs in it.

File:

• kernel/arch/amd64/src/asm.S (modified) (1 diff)

kernel/arch/amd64/src/asm.S

@@ -334 +334 @@
         movq %gs:8, %rsp  /* set this thread's kernel RSP */
         
-        /* Switch back to remain consistent */
+        /*
+         * Note that the space needed for the imitated istate structure has been
+         * preallocated for us in thread_create_arch() and set in
+         * before_thread_runs_arch().
+         */
+
+        /*
+         * Save the general purpose registers and push the 7th argument (syscall
+         * number) onto the stack. Note that the istate structure has a layout
+         * which supports this.
+         */
+        movq %rax, ISTATE_OFFSET_RAX(%rsp)  /* 7th argument, passed on stack */
+        movq %rbx, ISTATE_OFFSET_RBX(%rsp)  /* observability */
+        movq %rcx, ISTATE_OFFSET_RCX(%rsp)  /* userspace RIP */
+        movq %rdx, ISTATE_OFFSET_RDX(%rsp)  /* 3rd argument, observability */
+        movq %rsi, ISTATE_OFFSET_RSI(%rsp)  /* 2nd argument, observability */ 
+        movq %rdi, ISTATE_OFFSET_RDI(%rsp)  /* 1st argument, observability */
+        movq %rbp, ISTATE_OFFSET_RBP(%rsp)  /* need to preserve userspace RBP */
+        movq %r8, ISTATE_OFFSET_R8(%rsp)    /* 5th argument, observability */
+        movq %r9, ISTATE_OFFSET_R9(%rsp)    /* 6th argument, observability */
+        movq %r10, ISTATE_OFFSET_R10(%rsp)  /* 4th argument, observability */
+        movq %r11, ISTATE_OFFSET_R11(%rsp)  /* low 32 bits userspace RFLAGS */
+        movq %r12, ISTATE_OFFSET_R12(%rsp)  /* observability */
+        movq %r13, ISTATE_OFFSET_R13(%rsp)  /* observability */
+        movq %r14, ISTATE_OFFSET_R14(%rsp)  /* observability */
+        movq %r15, ISTATE_OFFSET_R15(%rsp)  /* observability */
+
+        /*
+         * Save the return address and the userspace stack on locations that
+         * would normally be taken by them.
+         */
+        movq %gs:0, %rax
+        movq %rax, ISTATE_OFFSET_RSP(%rsp)
+        movq %rcx, ISTATE_OFFSET_RIP(%rsp)
+
+        /*
+         * Imitate a regular stack frame linkage.
+         */
+        movq $0, ISTATE_OFFSET_RBP_FRAME(%rsp)
+        movq %rcx, ISTATE_OFFSET_RIP_FRAME(%rsp)
+        leaq ISTATE_OFFSET_RBP_FRAME(%rsp), %rbp
+
+        /* Switch back to normal %gs */
         swapgs
         sti
         
-        pushq %rcx
-        pushq %r11
-        pushq %rbp
-        
-        xorq %rbp, %rbp  /* stop the stack traces here */
-        
         /* Copy the 4th argument where it is expected  */
         movq %r10, %rcx
-        pushq %rax
-        
+
+        /*
+         * Call syscall_handler() with the 7th argument passed on stack.
+         */
         call syscall_handler
         
-        addq $8, %rsp
-        
-        popq %rbp
-        popq %r11
-        popq %rcx
-        
         cli
-        swapgs
-        
-        /* Restore the user RSP */
-        movq %gs:0, %rsp
-        swapgs
-        
+        
+        /*
+         * Restore registers needed for return via the SYSRET instruction and
+         * the clobbered preserved registers (i.e. RBP).
+         */
+        movq ISTATE_OFFSET_RBP(%rsp), %rbp
+        movq ISTATE_OFFSET_RCX(%rsp), %rcx
+        movq ISTATE_OFFSET_R11(%rsp), %r11
+        movq ISTATE_OFFSET_RSP(%rsp), %rsp
+
         sysretq