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Subject[PATCH v2 3/6] x86, asm: Change the 32-bit sysenter code to use sp0
Date
The ia32 sysenter code loaded the top of the kernel stack into rsp
by loading kernel_stack and then adjusting it. It can be simplified
to just read sp0 directly.

This requires the addition of a new asm-offsets entry for sp0.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
arch/x86/ia32/ia32entry.S | 3 +--
arch/x86/kernel/asm-offsets_64.c | 1 +
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index ed9746340363..719db63b35c4 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -113,8 +113,7 @@ ENTRY(ia32_sysenter_target)
CFI_DEF_CFA rsp,0
CFI_REGISTER rsp,rbp
SWAPGS_UNSAFE_STACK
- movq PER_CPU_VAR(kernel_stack), %rsp
- addq $(KERNEL_STACK_OFFSET),%rsp
+ movq PER_CPU_VAR(init_tss + TSS_sp0), %rsp
/*
* No need to follow this irqs on/off section: the syscall
* disabled irqs, here we enable it straight after entry:
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index fdcbb4d27c9f..5ce6f2da8763 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -81,6 +81,7 @@ int main(void)
#undef ENTRY

OFFSET(TSS_ist, tss_struct, x86_tss.ist);
+ OFFSET(TSS_sp0, tss_struct, x86_tss.sp0);
BLANK();

DEFINE(__NR_syscall_max, sizeof(syscalls_64) - 1);
--
2.1.0


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