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Subject[PATCH 13/18] x86 vDSO: ia32 sysenter_return
Date

This changes the 64-bit kernel's support for the 32-bit sysenter
instruction to use stored fields rather than constants for the
user-mode return address, as the 32-bit kernel does. This adds a
sysenter_return field to struct thread_info, as 32-bit has. There
is no observable effect from this yet. It makes the assembly code
independent of the 32-bit vDSO mapping address, paving the way for
making the vDSO address vary as it does on the 32-bit kernel.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/x86/ia32/ia32entry.S | 7 +++----
arch/x86/ia32/syscall32.c | 4 ++++
arch/x86/kernel/asm-offsets_64.c | 1 +
include/asm-x86/thread_info_64.h | 3 +++
4 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index df588f0..2499a32 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -12,7 +12,6 @@
#include <asm/ia32_unistd.h>
#include <asm/thread_info.h>
#include <asm/segment.h>
-#include <asm/vsyscall32.h>
#include <asm/irqflags.h>
#include <linux/linkage.h>

@@ -104,7 +103,7 @@ ENTRY(ia32_sysenter_target)
pushfq
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET rflags,0*/
- movl $VSYSCALL32_SYSEXIT, %r10d
+ movl 8*3-THREAD_SIZE+threadinfo_sysenter_return(%rsp), %r10d
CFI_REGISTER rip,r10
pushq $__USER32_CS
CFI_ADJUST_CFA_OFFSET 8
@@ -142,6 +141,8 @@ sysenter_do_call:
andl $~TS_COMPAT,threadinfo_status(%r10)
/* clear IF, that popfq doesn't enable interrupts early */
andl $~0x200,EFLAGS-R11(%rsp)
+ movl RIP-R11(%rsp),%edx /* User %eip */
+ CFI_REGISTER rip,rdx
RESTORE_ARGS 1,24,1,1,1,1
popfq
CFI_ADJUST_CFA_OFFSET -8
@@ -149,8 +150,6 @@ sysenter_do_call:
popq %rcx /* User %esp */
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rsp,rcx
- movl $VSYSCALL32_SYSEXIT,%edx /* User %eip */
- CFI_REGISTER rip,rdx
TRACE_IRQS_ON
swapgs
sti /* sti only takes effect after the next instruction */
diff --git a/arch/x86/ia32/syscall32.c b/arch/x86/ia32/syscall32.c
index 15013ba..2c9c145 100644
--- a/arch/x86/ia32/syscall32.c
+++ b/arch/x86/ia32/syscall32.c
@@ -45,6 +45,10 @@ int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
VM_ALWAYSDUMP,
syscall32_pages);
+ if (ret == 0) {
+ current->mm->context.vdso = (void __user *)VSYSCALL32_BASE;
+ current_thread_info()->sysenter_return = VSYSCALL32_SYSEXIT;
+ }
up_write(&mm->mmap_sem);
return ret;
}
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index d1b6ed9..1f9b0b5 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -47,6 +47,7 @@ int main(void)
ENTRY(addr_limit);
ENTRY(preempt_count);
ENTRY(status);
+ ENTRY(sysenter_return);
BLANK();
#undef ENTRY
#define ENTRY(entry) DEFINE(pda_ ## entry, offsetof(struct x8664_pda, entry))
diff --git a/include/asm-x86/thread_info_64.h b/include/asm-x86/thread_info_64.h
index beae2bf..f81638e 100644
--- a/include/asm-x86/thread_info_64.h
+++ b/include/asm-x86/thread_info_64.h
@@ -33,6 +33,9 @@ struct thread_info {

mm_segment_t addr_limit;
struct restart_block restart_block;
+#ifdef CONFIG_IA32_EMULATION
+ void __user *sysenter_return;
+#endif
};
#endif

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