libc: make MINIX assembly code position-independent
While here, simplify ucontext.S . makes libc link without the messy DT_TEXTREL warning. Change-Id: I4656d9068eab5ed2fa1e391242883d5dd9d93644
This commit is contained in:
Antoine Leca
Gerrit Code Review
parent
8e87bd84b4
commit
3a0aa55040
2 changed files with 47 additions and 78 deletions
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@ -6,4 +6,10 @@
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IMPORT(_sigreturn)
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ENTRY(__sigreturn)
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addl $16, %esp
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#ifndef PIC
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jmp _C_LABEL(_sigreturn)
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#else
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PIC_PROLOGUE /* push %ebx, but we do not care */
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pop %eax /* special knowledge of how PIC works: discard pushed EBX */
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jmp PIC_PLT(_C_LABEL(_sigreturn))
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#endif /* PIC */
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@ -1,26 +1,11 @@
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#include <machine/asm.h>
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#include <ucontextoffsets.h>
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#ifdef __ACK__
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.text
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begtext:
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#ifdef __ACK__
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.rom
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#else
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.data
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#endif
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begrom:
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.data
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begdata:
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.bss
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begbss:
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#endif
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IMPORT(getuctx)
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IMPORT(setuctx)
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IMPORT(resumecontext)
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.globl _C_LABEL(__errno)
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/* MCF_MAGIC value from <mcontext.h> */
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#define MCF_MAGIC 0xc0ffee
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@ -43,59 +28,41 @@ ENTRY(getcontext)
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* saving its signal mask, then we can skip the context switch to
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* PM and kernel altogether and only save general-purpose registers. */
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mov (%esp), %ecx /* Save return address:
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* When setcontext or swapcontext is called,
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* we jump to this address and continue
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* running. */
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mov 4(%esp), %edx /* edx = ucp */
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/* Check null pointer */
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cmp $0, %edx /* edx == NULL? */
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jne 3f /* Not null, continue */
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movl $EFAULT, (_C_LABEL(errno))
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PIC_PROLOGUE
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call PIC_PLT(_C_LABEL(__errno))
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PIC_EPILOGUE
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movl $EFAULT, (%eax)
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xor %eax, %eax
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dec %eax /* return -1 */
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ret
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3: /* Check flags */
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push %ecx /* save ecx */
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push %ebx /* save ebx */
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lea UC_FLAGS(%edx), %ebx /* ebx = &(ucp->uc_flags) */
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mov (%ebx), %ecx /* ecx = ucp->uc_flags */
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mov $UCF_IGNFPU, %eax
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or $UCF_IGNSIGM, %eax
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cmp %eax, %ecx /* is UCF_IGNFPU or UCF_IGNSIGM set? */
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pop %ebx /* restore ebx */
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pop %ecx /* restore ecx */
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jz 1f /* Both are set, skip getuctx */
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0:
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push %ecx /* Save ecx */
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mov UC_FLAGS(%edx), %eax /* eax = ucp->uc_flags */
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xor $[UCF_IGNFPU|UCF_IGNSIGM], %eax /* toggle both flags */
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jz 5f /* Both were set, skip getuctx */
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PIC_PROLOGUE
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push %edx
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call _C_LABEL(getuctx) /* getuctx(ucp) */
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call PIC_PLT(_C_LABEL(getuctx)) /* getuctx(ucp) */
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pop %edx /* clean up stack and restore edx */
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pop %ecx /* Restore ecx */
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PIC_EPILOGUE
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1:
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5:
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/* Save the context */
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mov 4(%esp), %edx /* edx = ucp */
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pop %eax /* retaddr */
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mov %eax, PC(%edx) /* Save real RTA in mcp struct */
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pop PC(%edx) /* Save real RTA in mcp struct */
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mov %esp, SP(%edx) /* Save stack pointer (now pointing to ucp) */
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/* Save GP registers */
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/* Save GP registers (except EAX and EDX) */
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mov %ebp, BP(%edx) /* Save EBP */
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mov %esi, SI(%edx) /* Save ESI */
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mov %edi, DI(%edx) /* Save EDI */
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mov %ebx, BX(%edx) /* Save EBX */
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mov %ecx, CX(%edx) /* Save ECX */
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movl $MCF_MAGIC, MAGIC(%edx) /* Set magic value */
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push %eax /* Restore retaddr */
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xor %eax, %eax /* Return 0 */
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2:
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add $4, %esp /* Remove stale (setcontext) RTA */
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jmp *%ecx /* Restore return address */
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jmp *PC(%edx) /* Return return address */
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/* int setcontext(const ucontext_t *ucp)
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@ -115,52 +82,43 @@ ENTRY(setcontext)
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/* Check null pointer */
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cmp $0, %edx /* edx == NULL? */
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jnz 3f /* Not null, continue */
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movl $EFAULT, (_C_LABEL(errno))
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movl $EFAULT, %edx
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0: push %edx /* preserve errno */
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PIC_PROLOGUE
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call PIC_PLT(_C_LABEL(__errno))
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PIC_EPILOGUE
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pop %edx
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movl %edx, (%eax)
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xor %eax, %eax
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dec %eax /* return -1 */
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ret
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3: /* Check flags */
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push %ebx /* save ebx */
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lea MAGIC(%edx), %ebx /* ebx = &(ucp->mc_context.mc_magic) */
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mov (%ebx), %ecx /* ecx = ucp->mc_context.mc_magic */
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pop %ebx /* restore ebx */
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cmp $MCF_MAGIC, %ecx /* is the magic value set (is context valid)?*/
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cmpl $MCF_MAGIC, MAGIC(%edx) /* is the magic value set (is context valid)?*/
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jz 4f /* is set, proceed */
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movl $EINVAL, (_C_LABEL(errno)) /* not set, return error code */
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xor %eax, %eax
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dec %eax /* return -1 */
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ret
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movl $EINVAL, %edx /* not set, return error code */
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jmp 0b
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4: push %ebx /* save ebx */
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lea UC_FLAGS(%edx), %ebx /* ebx = &(ucp->uc_flags) */
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mov (%ebx), %ecx /* ecx = ucp->uc_flags */
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pop %ebx /* restore ebx */
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mov $UCF_IGNFPU, %eax
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or $UCF_IGNSIGM, %eax
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cmp %eax, %ecx /* Are UCF_IGNFPU and UCF_IGNSIGM flags set? */
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jz 1f /* Both are set, so don't bother restoring FPU
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4: mov UC_FLAGS(%edx), %eax /* eax = ucp->uc_flags */
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xor $[UCF_IGNFPU|UCF_IGNSIGM], %eax /* toggle both flags */
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jz 5f /* Both are set, so don't bother restoring FPU
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* state and signal mask */
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0: push %ecx /* Save ecx */
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PIC_PROLOGUE
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push %edx
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call _C_LABEL(setuctx) /* setuctx(ucp) */
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call PIC_PLT(_C_LABEL(setuctx)) /* setuctx(ucp) */
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pop %edx /* Clean up stack and restore edx */
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pop %ecx /* Restore ecx */
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PIC_EPILOGUE
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1: /* Restore the registers */
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mov 4(%esp), %edx /* edx = ucp */
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5: /* Restore the registers (except EAX and EDX) */
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mov CX(%edx), %ecx /* Restore ECX */
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mov BX(%edx), %ebx /* Restore EBX */
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mov DI(%edx), %edi /* Restore EDI */
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mov SI(%edx), %esi /* Restore ESI */
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mov BP(%edx), %ebp /* Restore EBP */
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mov SP(%edx), %esp /* Restore stack pointer */
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2:
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jmp *PC(%edx) /* Push RTA onto stack so we can return to it */
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jmp *PC(%edx) /* Return to RTA */
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/* void ctx_start((void *func)(int arg1, ..., argn), arg1, ..., argn,
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* ucontext_t *ucp)
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@ -168,7 +126,11 @@ ENTRY(setcontext)
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* to ucp on the stack. By setting ESP to ESI, we effectively 'remove' all
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* arguments to `func' from the stack. Finally, a call to resumecontext
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* will start the next context in the linked list (or exit the program if
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* there is no context). */
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* there is no context).
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*
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* Since PIC needs the EBX register, which is pushed on the stack by
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* PIC_PROLOGUE, we need an extra of salsa here.
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*/
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ENTRY(ctx_start)
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/* 0(esp) -> func
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* 4(esp) -> arg1
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@ -178,9 +140,10 @@ ENTRY(ctx_start)
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pop %eax /* eax = func */
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call *%eax /* func(arg1, ..., argn) */
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mov %esi, %esp /* Clean up stack */
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PIC_PROLOGUE /* may push %ebx, but we do not care */
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mov %esi, %esp /* Clean up stack, keep %ebx = &GOT */
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/* ucp is now at the top of the stack again */
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call _C_LABEL(resumecontext) /* resumecontext(ucp) */
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call PIC_PLT(_C_LABEL(resumecontext)) /* resumecontext(ucp) */
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ret /* never reached */
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