From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C3A0C4332F for ; Thu, 24 Nov 2022 06:30:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229668AbiKXGa5 (ORCPT ); Thu, 24 Nov 2022 01:30:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229679AbiKXGax (ORCPT ); Thu, 24 Nov 2022 01:30:53 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F43CDAD28 for ; Wed, 23 Nov 2022 22:30:37 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 19CA561FEF for ; Thu, 24 Nov 2022 06:30:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B513BC433D6; Thu, 24 Nov 2022 06:30:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669271437; bh=LSSfW3Zh2RwJhUxrBUj2wRpVCu4TImcNtfrvTVyJ6T0=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=dIkR6A+6/KlvAkLyhTrsAdN67t8IlIYzfUMxh+erkNGSTZJBOtkPJOLVPEiqCVE0K Qgt4gK9at3st/MI0LmKN+3P2eBTcAxbdLwfGI3Tb7nc2uiGxyD48JXJJRrvFZ8R9aa fPdEwbDplC0tLgctsPvyiAXIdMJP7kjL0uhOsouYke6/go/AJQrD0XSemw/mx7k7ap OFRll7F6TFUhemoSAZgzma0YPPkDKADiaTAHeTxv8AdrO0oi9Go6VFaL6lc5HlWncP YW8olexFs9306wN2rPZc5sI/nkxnkmriuaGuCuIyV/cdJkVhT5fQ2DNELpmj3pS/as MRJm9gOwhYnrA== Date: Thu, 24 Nov 2022 06:30:35 +0000 From: Conor Dooley To: linux-riscv@lists.infradead.org, Deepak Gupta , palmer@dabbelt.com CC: linux-kernel@vger.kernel.org, paul.walmsley@sifive.com, Guo Ren , Jisheng Zhang Subject: Re: [PATCH] riscv: VMAP_STACK overflow detection thread-safe User-Agent: K-9 Mail for Android In-Reply-To: <20221124005006.1788315-1-debug@rivosinc.com> References: <20221124005006.1788315-1-debug@rivosinc.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hey Deepak, Guo Ren s issues aside, there's some process bits here=2E On 24 November 2022 00:50:06 GMT, Deepak Gupta wrot= e: >commit 31da94c25aea835ceac00575a9fd206c5a833fed added support for Please check the documentation for how to format commit references in patc= h text=2E As a reader, a hash requires access to a git tree to do anything with=2E Id show you the format but I am on my phone ;) >CONFIG_VMAP_STACK=2E If overflow is detected, CPU switches to `shadow_sta= ck` >temporarily before switching finally to per-cpu `overflow_stack`=2E > >If two CPUs/harts are racing and end up in over flowing kernel stack, one >or both will end up corrupting each other state because `shadow_stack` is >not per-cpu=2E > >Following are the changes in this patch > > - Defines an asm macro to obtain per-cpu symbols in destination > register=2E > - Computing per-cpu symbol requires a temporary register=2E When stack i= s > out of question, a place is needed to spill a register=2E `thread_info= ` > is good location to have spill register=2E > - In entry=2ES when overflow is detected x31 is spilled into thread_info= =2E > x31 is used as temp reg for asm macro to locate per-cpu overflow stack > >Other relevant disccussion on this >https://lore=2Ekernel=2Eorg/linux-riscv/Y347B0x4VUNOd6V7@xhacker/T/#t Link: foo > >Tested by `echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT` > >[ 286=2E223273] Insufficient stack space to handle exception!/debug/prov= oke-crash/DIRECT >[ 286=2E223878] Task stack: [0xff20000010a98000=2E=2E0xff20000010a9c= 000] >[ 286=2E224411] Overflow stack: [0xff600001f7d98370=2E=2E0xff600001f7d99= 370] >[ 286=2E226057] CPU: 1 PID: 205 Comm: bash Not tainted 6=2E1=2E0-rc2-000= 01-g328a1f96f7b9 #34 >[ 286=2E227139] Hardware name: riscv-virtio,qemu (DT) >[ 286=2E228000] epc : __memset+0x60/0xfc >[ 286=2E229299] ra : recursive_loop+0x48/0xc6 [lkdtm] >[ 286=2E231457] epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff2000= 0010a97e80 >[ 286=2E232207] gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff2000= 0010a97e88 >[ 286=2E233584] t1 : 000000000000002e t2 : 3233206874706564 s0 : ff2000= 0010a982b0 >[ 286=2E234293] s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 000000= 0000000000 >[ 286=2E234998] a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 000000= 0000000000 >[ 286=2E235697] a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007f= ffffffffff >[ 286=2E236384] s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff2000= 0010a9be90 >[ 286=2E237743] s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00ffff= fff0aa3684 >[ 286=2E238691] s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffff= ff8a7cad10 >[ 286=2E239591] s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffff= ff815dbaf4 >[ 286=2E240537] t5 : ffffffff815dbab8 t6 : ff20000010a9bb48 >[ 286=2E241540] status: 0000000200000120 badaddr: ff20000010a97e88 cause= : 000000000000000f >[ 286=2E242979] Kernel panic - not syncing: Kernel stack overflow >[ 286=2E244106] CPU: 1 PID: 205 Comm: bash Not tainted 6=2E1=2E0-rc2-000= 01-g328a1f96f7b9 #34 >[ 286=2E245276] Hardware name: riscv-virtio,qemu (DT) >[ 286=2E245929] Call Trace: >[ 286=2E246954] [] dump_backtrace+0x30/0x38 >[ 286=2E247813] [] show_stack+0x40/0x4c >[ 286=2E248429] [] dump_stack_lvl+0x44/0x5c >[ 286=2E249439] [] dump_stack+0x18/0x20 >[ 286=2E250056] [] panic+0x126/0x2fe >[ 286=2E250642] [] walk_stackframe+0x0/0xf0 >[ 286=2E251357] [] recursive_loop+0x48/0xc6 [lkdtm] >[ 286=2E253321] SMP: stopping secondary CPUs >[ 286=2E256724] ---[ end Kernel panic - not syncing: Kernel stack overfl= ow ]--- For stack traces, especially long ones, please cut out the timestamps=2E >Fixes: 31da94c25aea835ceac00575a9fd206c5a833fed https://gist=2Egithubusercontent=2Ecom/conor-pwbot/8882fc7ef7cd4fe83377457= 4fbf509f5/raw/d360ec7aebfaa6c2d043e9bd87f59745ad6a4c85/desc Please use the correct format for fixes tags=2E >Cc: Guo Ren >Cc: Jisheng Zhang > >Signed-off-by: Deepak Gupta All of the tags need to be in one block, so: Link: Fixes: SoB: Thanks, Conor=2E >--- > arch/riscv/include/asm/asm=2Eh | 11 ++++++ > arch/riscv/include/asm/thread_info=2Eh | 3 ++ > arch/riscv/kernel/asm-offsets=2Ec | 4 +++ > arch/riscv/kernel/entry=2ES | 54 ++++------------------------ > arch/riscv/kernel/traps=2Ec | 12 +------ > 5 files changed, 26 insertions(+), 58 deletions(-) > >diff --git a/arch/riscv/include/asm/asm=2Eh b/arch/riscv/include/asm/asm= =2Eh >index 1b471ff73178=2E=2E373eba843331 100644 >--- a/arch/riscv/include/asm/asm=2Eh >+++ b/arch/riscv/include/asm/asm=2Eh >@@ -69,6 +69,7 @@ >=20 > #ifdef __ASSEMBLY__ >=20 >+#include > /* Common assembly source macros */ >=20 > /* >@@ -80,6 +81,16 @@ > =2Eendr > =2Eendm >=20 >+=2Emacro asm_per_cpu dst sym tmp >+ REG_L \tmp, TASK_TI_CPU_NUM(tp) >+ slli \tmp, \tmp, 0x3 >+ la \dst, __per_cpu_offset >+ add \dst, \dst, \tmp >+ REG_L \tmp, 0(\dst) >+ la \dst, \sym >+ add \dst, \dst, \tmp >+=2Eendm >+ > #endif /* __ASSEMBLY__ */ >=20 > #endif /* _ASM_RISCV_ASM_H */ >diff --git a/arch/riscv/include/asm/thread_info=2Eh b/arch/riscv/include/= asm/thread_info=2Eh >index 67322f878e0d=2E=2E7e17dc07cf11 100644 >--- a/arch/riscv/include/asm/thread_info=2Eh >+++ b/arch/riscv/include/asm/thread_info=2Eh >@@ -65,6 +65,9 @@ struct thread_info { > */ > long kernel_sp; /* Kernel stack pointer */ > long user_sp; /* User stack pointer */ >+#ifdef CONFIG_VMAP_STACK >+ long spill_reg; /* per cpu scratch space to spill a single regis= ter */ >+#endif > int cpu; > }; >=20 >diff --git a/arch/riscv/kernel/asm-offsets=2Ec b/arch/riscv/kernel/asm-of= fsets=2Ec >index df9444397908=2E=2Ebed3c83bfb8f 100644 >--- a/arch/riscv/kernel/asm-offsets=2Ec >+++ b/arch/riscv/kernel/asm-offsets=2Ec >@@ -38,6 +38,10 @@ void asm_offsets(void) > OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info=2Ekernel_sp); > OFFSET(TASK_TI_USER_SP, task_struct, thread_info=2Euser_sp); >=20 >+ OFFSET(TASK_TI_CPU_NUM, task_struct, thread_info=2Ecpu); >+#ifdef CONFIG_VMAP_STACK >+ OFFSET(TASK_TI_SPILL_REG, task_struct, thread_info=2Espill_reg); >+#endif > OFFSET(TASK_THREAD_F0, task_struct, thread=2Efstate=2Ef[0]); > OFFSET(TASK_THREAD_F1, task_struct, thread=2Efstate=2Ef[1]); > OFFSET(TASK_THREAD_F2, task_struct, thread=2Efstate=2Ef[2]); >diff --git a/arch/riscv/kernel/entry=2ES b/arch/riscv/kernel/entry=2ES >index b9eda3fcbd6d=2E=2E12f285cec136 100644 >--- a/arch/riscv/kernel/entry=2ES >+++ b/arch/riscv/kernel/entry=2ES >@@ -10,9 +10,11 @@ > #include > #include > #include >+#include > #include > #include > #include >+#include >=20 > #if !IS_ENABLED(CONFIG_PREEMPTION) > =2Eset resume_kernel, restore_all >@@ -404,54 +406,12 @@ handle_syscall_trace_exit: >=20 > #ifdef CONFIG_VMAP_STACK > handle_kernel_stack_overflow: >- la sp, shadow_stack >- addi sp, sp, SHADOW_OVERFLOW_STACK_SIZE >+ REG_S x31, TASK_TI_SPILL_REG(tp) >+ asm_per_cpu sp, overflow_stack, x31 >+ li x31, OVERFLOW_STACK_SIZE >+ add sp, sp, x31 >+ REG_L x31, TASK_TI_SPILL_REG(tp) >=20 >- //save caller register to shadow stack >- addi sp, sp, -(PT_SIZE_ON_STACK) >- REG_S x1, PT_RA(sp) >- REG_S x5, PT_T0(sp) >- REG_S x6, PT_T1(sp) >- REG_S x7, PT_T2(sp) >- REG_S x10, PT_A0(sp) >- REG_S x11, PT_A1(sp) >- REG_S x12, PT_A2(sp) >- REG_S x13, PT_A3(sp) >- REG_S x14, PT_A4(sp) >- REG_S x15, PT_A5(sp) >- REG_S x16, PT_A6(sp) >- REG_S x17, PT_A7(sp) >- REG_S x28, PT_T3(sp) >- REG_S x29, PT_T4(sp) >- REG_S x30, PT_T5(sp) >- REG_S x31, PT_T6(sp) >- >- la ra, restore_caller_reg >- tail get_overflow_stack >- >-restore_caller_reg: >- //save per-cpu overflow stack >- REG_S a0, -8(sp) >- //restore caller register from shadow_stack >- REG_L x1, PT_RA(sp) >- REG_L x5, PT_T0(sp) >- REG_L x6, PT_T1(sp) >- REG_L x7, PT_T2(sp) >- REG_L x10, PT_A0(sp) >- REG_L x11, PT_A1(sp) >- REG_L x12, PT_A2(sp) >- REG_L x13, PT_A3(sp) >- REG_L x14, PT_A4(sp) >- REG_L x15, PT_A5(sp) >- REG_L x16, PT_A6(sp) >- REG_L x17, PT_A7(sp) >- REG_L x28, PT_T3(sp) >- REG_L x29, PT_T4(sp) >- REG_L x30, PT_T5(sp) >- REG_L x31, PT_T6(sp) >- >- //load per-cpu overflow stack >- REG_L sp, -8(sp) > addi sp, sp, -(PT_SIZE_ON_STACK) >=20 > //save context to overflow stack >diff --git a/arch/riscv/kernel/traps=2Ec b/arch/riscv/kernel/traps=2Ec >index f3e96d60a2ff=2E=2Eeef3a87514c7 100644 >--- a/arch/riscv/kernel/traps=2Ec >+++ b/arch/riscv/kernel/traps=2Ec >@@ -208,18 +208,8 @@ int is_valid_bugaddr(unsigned long pc) > #endif /* CONFIG_GENERIC_BUG */ >=20 > #ifdef CONFIG_VMAP_STACK >-static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], >+DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], > overflow_stack)__aligned(16); >-/* >- * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry=2ES) i= s used >- * to get per-cpu overflow stack(get_overflow_stack)=2E >- */ >-long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)]; >-asmlinkage unsigned long get_overflow_stack(void) >-{ >- return (unsigned long)this_cpu_ptr(overflow_stack) + >- OVERFLOW_STACK_SIZE; >-} >=20 > asmlinkage void handle_bad_stack(struct pt_regs *regs) > {