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Peter Anvin" , Fenghua Yu , Thomas Tai , "Chang S. Bae" , Masami Hiramatsu Subject: [PATCH V4 1/7] x86/traps: Move pt_regs only in fixup_bad_iret() Date: Fri, 18 Mar 2022 22:30:10 +0800 Message-Id: <20220318143016.124387-2-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20220318143016.124387-1-jiangshanlai@gmail.com> References: <20220318143016.124387-1-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan fixup_bad_iret() and sync_regs() have similar arguments and do similar work that copies full or partial pt_regs to a place and switches stack after return. They are quite the same, but fixup_bad_iret() not only copies the pt_regs but also the return address of error_entry() while sync_regs() copies the pt_regs only and the return address of error_entry() was preserved and handled in ASM code. This patch makes fixup_bad_iret() work like sync_regs() and the handling of the return address of error_entry() is moved in ASM code. It removes the need to use the struct bad_iret_stack, simplifies fixup_bad_iret() and makes the ASM error_entry() call fixup_bad_iret() as the same as calling sync_regs() which adds readability because the calling patterns are exactly the same. It is prepared for later patch to do the stack switch after the error_entry() which simplifies the code further. Signed-off-by: Lai Jiangshan --- arch/x86/entry/entry_64.S | 5 ++++- arch/x86/include/asm/traps.h | 2 +- arch/x86/kernel/traps.c | 17 ++++++----------- 3 files changed, 11 insertions(+), 13 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 4faac48ebec5..e9d896717ab4 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1058,9 +1058,12 @@ SYM_CODE_START_LOCAL(error_entry) * Pretend that the exception came from user mode: set up pt_regs * as if we faulted immediately after IRET. */ - mov %rsp, %rdi + popq %r12 /* save return addr in %12 */ + movq %rsp, %rdi /* arg0 = pt_regs pointer */ call fixup_bad_iret mov %rax, %rsp + ENCODE_FRAME_POINTER + pushq %r12 jmp .Lerror_entry_from_usermode_after_swapgs SYM_CODE_END(error_entry) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index 35317c5c551d..47ecfff2c83d 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -13,7 +13,7 @@ #ifdef CONFIG_X86_64 asmlinkage __visible notrace struct pt_regs *sync_regs(struct pt_regs *eregs); asmlinkage __visible notrace -struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s); +struct pt_regs *fixup_bad_iret(struct pt_regs *bad_regs); void __init trap_init(void); asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *eregs); #endif diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 1563fb995005..9fe9cd9d3eeb 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -892,13 +892,8 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r } #endif -struct bad_iret_stack { - void *error_entry_ret; - struct pt_regs regs; -}; - asmlinkage __visible noinstr -struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) +struct pt_regs *fixup_bad_iret(struct pt_regs *bad_regs) { /* * This is called from entry_64.S early in handling a fault @@ -908,19 +903,19 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) * just below the IRET frame) and we want to pretend that the * exception came from the IRET target. */ - struct bad_iret_stack tmp, *new_stack = - (struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; + struct pt_regs tmp, *new_stack = + (struct pt_regs *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; /* Copy the IRET target to the temporary storage. */ - __memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8); + __memcpy(&tmp.ip, (void *)bad_regs->sp, 5*8); /* Copy the remainder of the stack from the current stack. */ - __memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip)); + __memcpy(&tmp, bad_regs, offsetof(struct pt_regs, ip)); /* Update the entry stack */ __memcpy(new_stack, &tmp, sizeof(tmp)); - BUG_ON(!user_mode(&new_stack->regs)); + BUG_ON(!user_mode(new_stack)); return new_stack; } #endif -- 2.19.1.6.gb485710b