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| author | Andy Lutomirski <luto@kernel.org> | 2020-06-26 19:21:13 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-07-01 10:00:26 +0200 |
| commit | ffae641f57476369b4d503402b37ebe489d23395 (patch) | |
| tree | 66ad35049b3c31cf7256e2aa29ddbb1a420d2c8d /arch/x86/xen | |
| parent | x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C (diff) | |
| download | linux-ffae641f57476369b4d503402b37ebe489d23395.tar.xz linux-ffae641f57476369b4d503402b37ebe489d23395.zip | |
x86/entry/64/compat: Fix Xen PV SYSENTER frame setup
The SYSENTER frame setup was nonsense. It worked by accident because the
normal code into which the Xen asm jumped (entry_SYSENTER_32/compat) threw
away SP without touching the stack. entry_SYSENTER_compat was recently
modified such that it relied on having a valid stack pointer, so now the
Xen asm needs to invoke it with a valid stack.
Fix it up like SYSCALL: use the Xen-provided frame and skip the bare
metal prologue.
Fixes: 1c3e5d3f60e2 ("x86/entry: Make entry_64_compat.S objtool clean")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lkml.kernel.org/r/947880c41ade688ff4836f665d0c9fcaa9bd1201.1593191971.git.luto@kernel.org
Diffstat (limited to 'arch/x86/xen')
| -rw-r--r-- | arch/x86/xen/xen-asm_64.S | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S index 5d252aaeade8..e1e1c7eafa60 100644 --- a/arch/x86/xen/xen-asm_64.S +++ b/arch/x86/xen/xen-asm_64.S @@ -161,10 +161,22 @@ SYM_FUNC_END(xen_syscall32_target) /* 32-bit compat sysenter target */ SYM_FUNC_START(xen_sysenter_target) - mov 0*8(%rsp), %rcx - mov 1*8(%rsp), %r11 - mov 5*8(%rsp), %rsp - jmp entry_SYSENTER_compat + /* + * NB: Xen is polite and clears TF from EFLAGS for us. This means + * that we don't need to guard against single step exceptions here. + */ + popq %rcx + popq %r11 + + /* + * Neither Xen nor the kernel really knows what the old SS and + * CS were. The kernel expects __USER32_DS and __USER32_CS, so + * report those values even though Xen will guess its own values. + */ + movq $__USER32_DS, 4*8(%rsp) + movq $__USER32_CS, 1*8(%rsp) + + jmp entry_SYSENTER_compat_after_hwframe SYM_FUNC_END(xen_sysenter_target) #else /* !CONFIG_IA32_EMULATION */ |