diff options
Diffstat (limited to 'arch/x86/entry/common.c')
| -rw-r--r-- | arch/x86/entry/common.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 1b2606edc621..88dc5ba14d47 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -363,7 +363,8 @@ __visible void do_int80_syscall_32(struct pt_regs *regs) syscall_return_slowpath(regs); } -__visible void do_fast_syscall_32(struct pt_regs *regs) +/* Returns 0 to return using IRET or 1 to return using SYSRETL. */ +__visible long do_fast_syscall_32(struct pt_regs *regs) { /* * Called using the internal vDSO SYSENTER/SYSCALL32 calling @@ -395,12 +396,28 @@ __visible void do_fast_syscall_32(struct pt_regs *regs) enter_from_user_mode(); #endif prepare_exit_to_usermode(regs); - return; + return 0; /* Keep it simple: use IRET. */ } local_irq_disable(); /* Now this is just like a normal syscall. */ do_int80_syscall_32(regs); - return; + +#ifdef CONFIG_X86_64 + /* + * Opportunistic SYSRETL: if possible, try to return using SYSRETL. + * SYSRETL is available on all 64-bit CPUs, so we don't need to + * bother with SYSEXIT. + * + * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP, + * because the ECX fixup above will ensure that this is essentially + * never the case. + */ + return regs->cs == __USER32_CS && regs->ss == __USER_DS && + regs->ip == landing_pad && + (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0; +#else + return 0; +#endif } #endif |