Changeset 296426ad in mainline

Timestamp:

2007-11-16T16:17:18Z (16 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

9c2fb97

Parents:

e686744c

Message:

Support for 6 syscalls arguments on amd64.

Files:

• kernel/arch/amd64/include/proc/thread.h (modified) (1 diff)
• kernel/arch/amd64/src/asm_utils.S (modified) (2 diffs)
• kernel/arch/amd64/src/proc/scheduler.c (modified) (2 diffs)
• kernel/arch/amd64/src/proc/thread.c (modified) (1 diff)
• kernel/arch/amd64/src/syscall.c (modified) (1 diff)
• uspace/lib/libc/arch/amd64/src/fibril.S (modified) (1 diff)
• uspace/lib/libc/arch/amd64/src/syscall.S (modified) (1 diff)

kernel/arch/amd64/include/proc/thread.h

@@ -36 +36 @@
 #define KERN_amd64_THREAD_H_
 
+/* CAUTION: keep these in sync with low level assembly code in syscall_entry */
+#define SYSCALL_USTACK_RSP      0
+#define SYSCALL_KSTACK_RSP      1
+
 typedef struct {
         unative_t tls;
+        /** User and kernel RSP for syscalls. */
+        uint64_t syscall_rsp[2];        
 } thread_arch_t;
 

kernel/arch/amd64/src/asm_utils.S

@@ -221 +221 @@
 
         /*
-         * Choose between version with error code and version without error code.
-         * Both versions have to be of the same size. amd64 assembly is, however,
-         * a little bit tricky. For instance, subq $0x80, %rsp and subq $0x78, %rsp
-         * can result in two instructions with different op-code lengths.
+         * Choose between version with error code and version without error
+         * code. Both versions have to be of the same size. amd64 assembly is,
+         * however, a little bit tricky. For instance, subq $0x80, %rsp and
+         * subq $0x78, %rsp can result in two instructions with different
+         * op-code lengths.
          * Therefore we align the interrupt handlers.
          */
@@ -270 +271 @@
 h_end:
 
-        
+## Low-level syscall handler
+# 
+# Registers on entry:
+#
+# @param rcx            Userspace return address.
+# @param r11            Userspace RLFAGS.
+#
+# @param rax            Syscall number.
+# @param rdi            1st syscall argument.
+# @param rsi            2nd syscall argument.
+# @param rdx            3rd syscall argument.
+# @param r10            4th syscall argument. Used instead of RCX because the
+#                       SYSCALL instruction clobbers it.
+# @param r8             5th syscall argument.
+# @param r9             6th syscall argument.
+#
+# @return               Return value is in rax.
+#
 syscall_entry:
-        # Switch to hidden gs   
-        swapgs
-        # %gs:0 now points to pointer to stack page
-        mov %gs:0, %r10     # We have a ptr to stack page in r10
-        addq $PAGE_SIZE-16, %r10 # We need some space to store old %sp
-        
-        movq %rsp, 0(%r10)  # Save old stack pointer to stack
-        movq %r10, %rsp     # Change to new stack
-        pushq %rcx          # Return address
-        pushq %r11          # Save flags
-
-        # Switch back to remain consistent
-        swapgs 
-
+        swapgs                  # Switch to hidden gs   
+        # 
+        # %gs:0                 Scratch space for this thread's user RSP
+        # %gs:8                 Address to be used as this thread's kernel RSP
+        #
+        movq %rsp, %gs:0        # Save this thread's user RSP
+        movq %gs:8, %rsp        # Set this thread's kernel RSP
+        swapgs                  # Switch back to remain consistent
         sti
-        movq %r9, %rcx      # Exchange last parameter as a third
-        
+        
+        pushq %rcx
+        pushq %r11
+
+        movq %r10, %rcx         # Copy the 4th argument where it is expected 
+        pushq %rax
         call syscall_handler
-        cli                 # We will be touching stack pointer
+        addq $8, %rsp
                 
         popq %r11
         popq %rcx
-        movq 0(%rsp), %rsp
+
+        cli
+        swapgs
+        movq %gs:0, %rsp        # Restore the user RSP
+        swapgs
+
         sysretq
-                
-                
+
 .data
 .global interrupt_handler_size

kernel/arch/amd64/src/proc/scheduler.c

@@ -57 +57 @@
 void before_thread_runs_arch(void)
 {
-        CPU->arch.tss->rsp0 = (uintptr_t) &THREAD->kstack[THREAD_STACK_SIZE-SP_DELTA];
+        CPU->arch.tss->rsp0 =
+            (uintptr_t) &THREAD->kstack[THREAD_STACK_SIZE - SP_DELTA];
 
-        /* Syscall support - write address of thread stack pointer to 
-         * hidden part of gs */
+        /*
+         * Syscall support.
+         */
         swapgs();
-        write_msr(AMD_MSR_GS, (uint64_t)&THREAD->kstack);
+        write_msr(AMD_MSR_GS, (uintptr_t)THREAD->arch.syscall_rsp);
         swapgs();
 
@@ -72 +74 @@
         if (CPU->id < BKPOINTS_MAX)
                 breakpoint_add(&((the_t *) THREAD->kstack)->as, 
-                               BKPOINT_WRITE | BKPOINT_CHECK_ZERO,
-                               CPU->id);
+                    BKPOINT_WRITE | BKPOINT_CHECK_ZERO, CPU->id);
 #endif
 }

kernel/arch/amd64/src/proc/thread.c

@@ -42 +42 @@
 {
         t->arch.tls = 0;
+        t->arch.syscall_rsp[SYSCALL_USTACK_RSP] = 0;
+        /*
+         * Kernel RSP can be precalculated at thread creation time.
+         */
+        t->arch.syscall_rsp[SYSCALL_KSTACK_RSP] =
+            (uintptr_t)&t->kstack[PAGE_SIZE - sizeof(uint64_t)];
 }
 

kernel/arch/amd64/src/syscall.c

@@ -53 +53 @@
         /* Setup syscall entry address */
         
-        /* This is _mess_ - the 64-bit CS is argument+16,
-         * the SS is argument+8. The order is:
+        /* This is _mess_ - the 64-bit CS is argument + 16,
+         * the SS is argument + 8. The order is:
          * +0(KDATA_DES), +8(UDATA_DES), +16(UTEXT_DES)
          */
         write_msr(AMD_MSR_STAR,
-                  ((uint64_t)(gdtselector(KDATA_DES) | PL_USER)<<48) \
-                  | ((uint64_t)(gdtselector(KTEXT_DES) | PL_KERNEL)<<32));
+            ((uint64_t)(gdtselector(KDATA_DES) | PL_USER) << 48) |
+            ((uint64_t)(gdtselector(KTEXT_DES) | PL_KERNEL) << 32));
         write_msr(AMD_MSR_LSTAR, (uint64_t)syscall_entry);
         /* Mask RFLAGS on syscall 

uspace/lib/libc/arch/amd64/src/fibril.S

@@ -81 +81 @@
         # Set thread local storage
         movq OFFSET_TLS(%rdi), %rdi   # Set arg1 to TLS addr
-        movq $1, %r8
+        movq $1, %rax           # SYS_TLS_SET
         syscall
 

uspace/lib/libc/arch/amd64/src/syscall.S

@@ -29 +29 @@
 .text
         
-.globl __syscall
+.global __syscall
+        
+## Make a system call.
+#
+# @param rdi            First argument.
+# @param rsi            Second argument.
+# @param rdx            Third argument.
+# @param rcx            Fourth argument.
+# @param r8             Fifth argument.
+# @param r9             Sixth argument.
+# @param 8(%rsp)        Syscall number.
+#
+# @return               The return value will be stored in RAX.
+#
+__syscall:
+        #
+        # Move the syscall number into RAX.
+        movslq 8(%rsp), %rax
 
-        
-__syscall:
-        # rcx gets rewritten on syscall
-        movq %rcx, %r9
+        #
+        # Save RCX, the 4th argument, aside because RCX gets rewritten by the
+        # SYSCALL instruction.
+        #
+        movq %rcx, %r10
         syscall
         ret
-        
-.end __syscall
+