uce means uncorrectable memory error.
In the sea fault handling process of the kernel, if it is judged that the
RAS error is consumed in the kernel, the current processing is kernel panic
. However, it is not optimal. In some case, the page accessed in kernel is
a user page (such as copy_from_user/get_user), in this case, kill the user
process and isolate the user page with hardware error is a better choice.
This feature provides the option. We implement it to add new extable type
(XXX_UCE_RECOVERY), these new types indicates they can be fixup from
uncorrectable memory error and it is fixuped in do_sea(). If the exception
is fixuped correctly, the kernel can avoid panic.
In copy_from_user, record the exception reason to regs->regs[0] at
ex_handler_fixup_uce_recovery() which is used to check sea fault triggered.
In get_user, the processing of EX_TYPE_UACCESS_ERR_ZERO and
EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY is same and both return -EFAULT.
Signed-off-by: Tong Tiangen <[email protected]>
---
arch/arm64/Kconfig | 10 ++++++++
arch/arm64/include/asm/asm-extable.h | 35 ++++++++++++++++++++++++----
arch/arm64/include/asm/asm-uaccess.h | 16 +++++++++++++
arch/arm64/include/asm/esr.h | 5 ++++
arch/arm64/include/asm/extable.h | 2 +-
arch/arm64/include/asm/uaccess.h | 2 +-
arch/arm64/kernel/probes/kprobes.c | 2 +-
arch/arm64/lib/copy_from_user.S | 11 +++++----
arch/arm64/mm/extable.c | 21 ++++++++++++++++-
arch/arm64/mm/fault.c | 30 +++++++++++++++++++++++-
10 files changed, 119 insertions(+), 15 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 962c84952c98..39f828c5b931 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1681,6 +1681,16 @@ config ARM64_CNP
at runtime, and does not affect PEs that do not implement
this feature.
+config ARM64_UCE_KERNEL_RECOVERY
+ bool "Enable support for uncorrectable memory error(uce) kernel recovery"
+ default y
+ depends on ACPI_APEI_SEA
+ help
+ With ARM v8.2 RAS Extension, SEA are usually triggered when memory
+ error are consumed. In some cases, if the error address is in a
+ user page there is a chance to recover. we can isolate this page
+ and killing process instead of die.
+
endmenu
menu "ARMv8.3 architectural features"
diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
index c39f2437e08e..9debab58c2b2 100644
--- a/arch/arm64/include/asm/asm-extable.h
+++ b/arch/arm64/include/asm/asm-extable.h
@@ -2,11 +2,19 @@
#ifndef __ASM_ASM_EXTABLE_H
#define __ASM_ASM_EXTABLE_H
-#define EX_TYPE_NONE 0
-#define EX_TYPE_FIXUP 1
-#define EX_TYPE_BPF 2
-#define EX_TYPE_UACCESS_ERR_ZERO 3
-#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4
+#define EX_TYPE_NONE 0
+#define EX_TYPE_FIXUP 1
+#define EX_TYPE_BPF 2
+#define EX_TYPE_UACCESS_ERR_ZERO 3
+#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4
+
+/* _UCE_RECOVERY indicates that can fixup from unrecoverable memory errors */
+#define EX_TYPE_FIXUP_UCE_RECOVERY 5
+#define EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY 6
+
+#define IS_EX_TYPE_UCE_RECOVERY(type) \
+ (type == EX_TYPE_FIXUP_UCE_RECOVERY || \
+ type == EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY)
#ifdef __ASSEMBLY__
@@ -27,6 +35,14 @@
__ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
.endm
+/*
+ * Create an exception table entry for `insn`, which will branch to `fixup`
+ * when an unhandled fault(include sea fault) is taken.
+ */
+ .macro _asm_extable_uce_recovery, insn, fixup
+ __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP_UCE_RECOVERY, 0)
+ .endm
+
/*
* Create an exception table entry for `insn` if `fixup` is provided. Otherwise
* do nothing.
@@ -64,6 +80,15 @@
#define EX_DATA_REG(reg, gpr) \
"((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"
+#define _ASM_EXTABLE_UACCESS_ERR_ZERO_UCE_RECOVERY(insn, fixup, err, zero) \
+ __DEFINE_ASM_GPR_NUMS \
+ __ASM_EXTABLE_RAW(#insn, #fixup, \
+ __stringify(EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY), \
+ "(" \
+ EX_DATA_REG(ERR, err) " | " \
+ EX_DATA_REG(ZERO, zero) \
+ ")")
+
#define _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero) \
__DEFINE_ASM_GPR_NUMS \
__ASM_EXTABLE_RAW(#insn, #fixup, \
diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index 0557af834e03..36692ec1fdbb 100644
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -92,4 +92,20 @@ alternative_else_nop_endif
_asm_extable 8888b,\l;
.endm
+
+ .macro user_ldp_uce_recovery l, reg1, reg2, addr, post_inc
+8888: ldtr \reg1, [\addr];
+8889: ldtr \reg2, [\addr, #8];
+ add \addr, \addr, \post_inc;
+
+ _asm_extable_uce_recovery 8888b, \l;
+ _asm_extable_uce_recovery 8889b, \l;
+ .endm
+
+ .macro user_ldst_uce_recovery l, inst, reg, addr, post_inc
+8888: \inst \reg, [\addr];
+ add \addr, \addr, \post_inc;
+
+ _asm_extable_uce_recovery 8888b, \l;
+ .endm
#endif
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index d52a0b269ee8..11fcfc002654 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -330,6 +330,11 @@
#ifndef __ASSEMBLY__
#include <asm/types.h>
+static inline bool esr_is_sea(u32 esr)
+{
+ return (esr & ESR_ELx_FSC) == ESR_ELx_FSC_EXTABT;
+}
+
static inline bool esr_is_data_abort(u32 esr)
{
const u32 ec = ESR_ELx_EC(esr);
diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h
index 72b0e71cc3de..f7835b0f473b 100644
--- a/arch/arm64/include/asm/extable.h
+++ b/arch/arm64/include/asm/extable.h
@@ -45,5 +45,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex,
}
#endif /* !CONFIG_BPF_JIT */
-bool fixup_exception(struct pt_regs *regs);
+bool fixup_exception(struct pt_regs *regs, unsigned int esr);
#endif
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index e8dce0cc5eaa..a229f86e6542 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -236,7 +236,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
asm volatile( \
"1: " load " " reg "1, [%2]\n" \
"2:\n" \
- _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \
+ _ASM_EXTABLE_UACCESS_ERR_ZERO_UCE_RECOVERY(1b, 2b, %w0, %w1) \
: "+r" (err), "=&r" (x) \
: "r" (addr))
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d9dfa82c1f18..16a069e8eec3 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -285,7 +285,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
- if (fixup_exception(regs))
+ if (fixup_exception(regs, fsr))
return 1;
}
return 0;
diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
index 34e317907524..f16104c63dde 100644
--- a/arch/arm64/lib/copy_from_user.S
+++ b/arch/arm64/lib/copy_from_user.S
@@ -21,7 +21,7 @@
*/
.macro ldrb1 reg, ptr, val
- user_ldst 9998f, ldtrb, \reg, \ptr, \val
+ user_ldst_uce_recovery 9998f, ldtrb, \reg, \ptr, \val
.endm
.macro strb1 reg, ptr, val
@@ -29,7 +29,7 @@
.endm
.macro ldrh1 reg, ptr, val
- user_ldst 9997f, ldtrh, \reg, \ptr, \val
+ user_ldst_uce_recovery 9997f, ldtrh, \reg, \ptr, \val
.endm
.macro strh1 reg, ptr, val
@@ -37,7 +37,7 @@
.endm
.macro ldr1 reg, ptr, val
- user_ldst 9997f, ldtr, \reg, \ptr, \val
+ user_ldst_uce_recovery 9997f, ldtr, \reg, \ptr, \val
.endm
.macro str1 reg, ptr, val
@@ -45,7 +45,7 @@
.endm
.macro ldp1 reg1, reg2, ptr, val
- user_ldp 9997f, \reg1, \reg2, \ptr, \val
+ user_ldp_uce_recovery 9997f, \reg1, \reg2, \ptr, \val
.endm
.macro stp1 reg1, reg2, ptr, val
@@ -62,7 +62,8 @@ SYM_FUNC_START(__arch_copy_from_user)
ret
// Exception fixups
-9997: cmp dst, dstin
+9997: cbz x0, 9998f
+ cmp dst, dstin
b.ne 9998f
// Before being absolutely sure we couldn't copy anything, try harder
USER(9998f, ldtrb tmp1w, [srcin])
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index 489455309695..b6b76e839b4b 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -9,6 +9,7 @@
#include <asm/asm-extable.h>
#include <asm/ptrace.h>
+#include <asm/esr.h>
static inline unsigned long
get_ex_fixup(const struct exception_table_entry *ex)
@@ -23,6 +24,18 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex,
return true;
}
+static bool ex_handler_fixup_uce_recovery(const struct exception_table_entry *ex,
+ struct pt_regs *regs, unsigned int esr)
+{
+ if (esr_is_sea(esr))
+ regs->regs[0] = 0;
+ else
+ regs->regs[0] = 1;
+
+ regs->pc = get_ex_fixup(ex);
+ return true;
+}
+
static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
@@ -63,7 +76,7 @@ ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
return true;
}
-bool fixup_exception(struct pt_regs *regs)
+bool fixup_exception(struct pt_regs *regs, unsigned int esr)
{
const struct exception_table_entry *ex;
@@ -71,12 +84,18 @@ bool fixup_exception(struct pt_regs *regs)
if (!ex)
return false;
+ if (esr_is_sea(esr) && !IS_EX_TYPE_UCE_RECOVERY(ex->type))
+ return false;
+
switch (ex->type) {
case EX_TYPE_FIXUP:
return ex_handler_fixup(ex, regs);
+ case EX_TYPE_FIXUP_UCE_RECOVERY:
+ return ex_handler_fixup_uce_recovery(ex, regs, esr);
case EX_TYPE_BPF:
return ex_handler_bpf(ex, regs);
case EX_TYPE_UACCESS_ERR_ZERO:
+ case EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY:
return ex_handler_uaccess_err_zero(ex, regs);
case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
return ex_handler_load_unaligned_zeropad(ex, regs);
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 77341b160aca..47c447554d2a 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -361,7 +361,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr,
* Are we prepared to handle this kernel fault?
* We are almost certainly not prepared to handle instruction faults.
*/
- if (!is_el1_instruction_abort(esr) && fixup_exception(regs))
+ if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr))
return;
if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs),
@@ -695,6 +695,30 @@ static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs)
return 1; /* "fault" */
}
+static bool arm64_process_kernel_sea(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs, int sig, int code)
+{
+ if (!IS_ENABLED(CONFIG_ARM64_UCE_KERNEL_RECOVERY))
+ return false;
+
+ if (user_mode(regs) || !current->mm)
+ return false;
+
+ if (apei_claim_sea(regs) < 0)
+ return false;
+
+ current->thread.fault_address = 0;
+ current->thread.fault_code = esr;
+
+ if (!fixup_exception(regs, esr))
+ return false;
+
+ arm64_force_sig_fault(sig, code, addr,
+ "Uncorrected hardware memory error in kernel-access\n");
+
+ return true;
+}
+
static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs)
{
const struct fault_info *inf;
@@ -720,6 +744,10 @@ static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs)
*/
siaddr = untagged_addr(far);
}
+
+ if (arm64_process_kernel_sea(siaddr, esr, regs, inf->sig, inf->code))
+ return 0;
+
arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
return 0;
--
2.18.0.huawei.25
Hi, Tiangen,
在 2022/3/23 AM11:37, Tong Tiangen 写道:
> uce means uncorrectable memory error.
>
> In the sea fault handling process of the kernel, if it is judged that the
> RAS error is consumed in the kernel, the current processing is kernel panic
> . However, it is not optimal. In some case, the page accessed in kernel is
> a user page (such as copy_from_user/get_user), in this case, kill the user
> process and isolate the user page with hardware error is a better choice.
>
> This feature provides the option. We implement it to add new extable type
> (XXX_UCE_RECOVERY), these new types indicates they can be fixup from
> uncorrectable memory error and it is fixuped in do_sea(). If the exception
> is fixuped correctly, the kernel can avoid panic.
>
> In copy_from_user, record the exception reason to regs->regs[0] at
> ex_handler_fixup_uce_recovery() which is used to check sea fault triggered.
>
> In get_user, the processing of EX_TYPE_UACCESS_ERR_ZERO and
> EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY is same and both return -EFAULT.
>
> Signed-off-by: Tong Tiangen <[email protected]>
> ---
> arch/arm64/Kconfig | 10 ++++++++
> arch/arm64/include/asm/asm-extable.h | 35 ++++++++++++++++++++++++----
> arch/arm64/include/asm/asm-uaccess.h | 16 +++++++++++++
> arch/arm64/include/asm/esr.h | 5 ++++
> arch/arm64/include/asm/extable.h | 2 +-
> arch/arm64/include/asm/uaccess.h | 2 +-
> arch/arm64/kernel/probes/kprobes.c | 2 +-
> arch/arm64/lib/copy_from_user.S | 11 +++++----
> arch/arm64/mm/extable.c | 21 ++++++++++++++++-
> arch/arm64/mm/fault.c | 30 +++++++++++++++++++++++-
> 10 files changed, 119 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 962c84952c98..39f828c5b931 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1681,6 +1681,16 @@ config ARM64_CNP
> at runtime, and does not affect PEs that do not implement
> this feature.
>
> +config ARM64_UCE_KERNEL_RECOVERY
> + bool "Enable support for uncorrectable memory error(uce) kernel recovery"
> + default y
> + depends on ACPI_APEI_SEA
> + help
> + With ARM v8.2 RAS Extension, SEA are usually triggered when memory
> + error are consumed. In some cases, if the error address is in a
> + user page there is a chance to recover. we can isolate this page
> + and killing process instead of die.
> +
> endmenu
>
> menu "ARMv8.3 architectural features"
> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
> index c39f2437e08e..9debab58c2b2 100644
> --- a/arch/arm64/include/asm/asm-extable.h
> +++ b/arch/arm64/include/asm/asm-extable.h
> @@ -2,11 +2,19 @@
> #ifndef __ASM_ASM_EXTABLE_H
> #define __ASM_ASM_EXTABLE_H
>
> -#define EX_TYPE_NONE 0
> -#define EX_TYPE_FIXUP 1
> -#define EX_TYPE_BPF 2
> -#define EX_TYPE_UACCESS_ERR_ZERO 3
> -#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4
> +#define EX_TYPE_NONE 0
> +#define EX_TYPE_FIXUP 1
> +#define EX_TYPE_BPF 2
> +#define EX_TYPE_UACCESS_ERR_ZERO 3
> +#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4
> +
> +/* _UCE_RECOVERY indicates that can fixup from unrecoverable memory errors */
> +#define EX_TYPE_FIXUP_UCE_RECOVERY 5
> +#define EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY 6
> +
> +#define IS_EX_TYPE_UCE_RECOVERY(type) \
> + (type == EX_TYPE_FIXUP_UCE_RECOVERY || \
> + type == EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY)
>
> #ifdef __ASSEMBLY__
>
> @@ -27,6 +35,14 @@
> __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
> .endm
>
> +/*
> + * Create an exception table entry for `insn`, which will branch to `fixup`
> + * when an unhandled fault(include sea fault) is taken.
> + */
> + .macro _asm_extable_uce_recovery, insn, fixup
> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP_UCE_RECOVERY, 0)
> + .endm
> +
> /*
> * Create an exception table entry for `insn` if `fixup` is provided. Otherwise
> * do nothing.
> @@ -64,6 +80,15 @@
> #define EX_DATA_REG(reg, gpr) \
> "((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"
>
> +#define _ASM_EXTABLE_UACCESS_ERR_ZERO_UCE_RECOVERY(insn, fixup, err, zero) \
> + __DEFINE_ASM_GPR_NUMS \
> + __ASM_EXTABLE_RAW(#insn, #fixup, \
> + __stringify(EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY), \
> + "(" \
> + EX_DATA_REG(ERR, err) " | " \
> + EX_DATA_REG(ZERO, zero) \
> + ")")
> +
> #define _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero) \
> __DEFINE_ASM_GPR_NUMS \
> __ASM_EXTABLE_RAW(#insn, #fixup, \
> diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
> index 0557af834e03..36692ec1fdbb 100644
> --- a/arch/arm64/include/asm/asm-uaccess.h
> +++ b/arch/arm64/include/asm/asm-uaccess.h
> @@ -92,4 +92,20 @@ alternative_else_nop_endif
>
> _asm_extable 8888b,\l;
> .endm
> +
> + .macro user_ldp_uce_recovery l, reg1, reg2, addr, post_inc
> +8888: ldtr \reg1, [\addr];
> +8889: ldtr \reg2, [\addr, #8];
> + add \addr, \addr, \post_inc;
> +
> + _asm_extable_uce_recovery 8888b, \l;
> + _asm_extable_uce_recovery 8889b, \l;
> + .endm
> +
> + .macro user_ldst_uce_recovery l, inst, reg, addr, post_inc
> +8888: \inst \reg, [\addr];
> + add \addr, \addr, \post_inc;
> +
> + _asm_extable_uce_recovery 8888b, \l;
> + .endm
> #endif
> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
> index d52a0b269ee8..11fcfc002654 100644
> --- a/arch/arm64/include/asm/esr.h
> +++ b/arch/arm64/include/asm/esr.h
> @@ -330,6 +330,11 @@
> #ifndef __ASSEMBLY__
> #include <asm/types.h>
>
> +static inline bool esr_is_sea(u32 esr)
> +{
> + return (esr & ESR_ELx_FSC) == ESR_ELx_FSC_EXTABT;
> +}
> +
> static inline bool esr_is_data_abort(u32 esr)
> {
> const u32 ec = ESR_ELx_EC(esr);
> diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h
> index 72b0e71cc3de..f7835b0f473b 100644
> --- a/arch/arm64/include/asm/extable.h
> +++ b/arch/arm64/include/asm/extable.h
> @@ -45,5 +45,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex,
> }
> #endif /* !CONFIG_BPF_JIT */
>
> -bool fixup_exception(struct pt_regs *regs);
> +bool fixup_exception(struct pt_regs *regs, unsigned int esr);
> #endif
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index e8dce0cc5eaa..a229f86e6542 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -236,7 +236,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
> asm volatile( \
> "1: " load " " reg "1, [%2]\n" \
> "2:\n" \
> - _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \
> + _ASM_EXTABLE_UACCESS_ERR_ZERO_UCE_RECOVERY(1b, 2b, %w0, %w1) \
> : "+r" (err), "=&r" (x) \
> : "r" (addr))
>
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index d9dfa82c1f18..16a069e8eec3 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -285,7 +285,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
> * In case the user-specified fault handler returned
> * zero, try to fix up.
> */
> - if (fixup_exception(regs))
> + if (fixup_exception(regs, fsr))
> return 1;
> }
> return 0;
> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
> index 34e317907524..f16104c63dde 100644
> --- a/arch/arm64/lib/copy_from_user.S
> +++ b/arch/arm64/lib/copy_from_user.S
> @@ -21,7 +21,7 @@
> */
>
> .macro ldrb1 reg, ptr, val
> - user_ldst 9998f, ldtrb, \reg, \ptr, \val
> + user_ldst_uce_recovery 9998f, ldtrb, \reg, \ptr, \val
> .endm
>
> .macro strb1 reg, ptr, val
> @@ -29,7 +29,7 @@
> .endm
>
> .macro ldrh1 reg, ptr, val
> - user_ldst 9997f, ldtrh, \reg, \ptr, \val
> + user_ldst_uce_recovery 9997f, ldtrh, \reg, \ptr, \val
> .endm
>
> .macro strh1 reg, ptr, val
> @@ -37,7 +37,7 @@
> .endm
>
> .macro ldr1 reg, ptr, val
> - user_ldst 9997f, ldtr, \reg, \ptr, \val
> + user_ldst_uce_recovery 9997f, ldtr, \reg, \ptr, \val
> .endm
>
> .macro str1 reg, ptr, val
> @@ -45,7 +45,7 @@
> .endm
>
> .macro ldp1 reg1, reg2, ptr, val
> - user_ldp 9997f, \reg1, \reg2, \ptr, \val
> + user_ldp_uce_recovery 9997f, \reg1, \reg2, \ptr, \val
> .endm
>
> .macro stp1 reg1, reg2, ptr, val
> @@ -62,7 +62,8 @@ SYM_FUNC_START(__arch_copy_from_user)
> ret
>
> // Exception fixups
> -9997: cmp dst, dstin
> +9997: cbz x0, 9998f
> + cmp dst, dstin
> b.ne 9998f
> // Before being absolutely sure we couldn't copy anything, try harder
> USER(9998f, ldtrb tmp1w, [srcin])
> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
> index 489455309695..b6b76e839b4b 100644
> --- a/arch/arm64/mm/extable.c
> +++ b/arch/arm64/mm/extable.c
> @@ -9,6 +9,7 @@
>
> #include <asm/asm-extable.h>
> #include <asm/ptrace.h>
> +#include <asm/esr.h>
>
> static inline unsigned long
> get_ex_fixup(const struct exception_table_entry *ex)
> @@ -23,6 +24,18 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex,
> return true;
> }
>
> +static bool ex_handler_fixup_uce_recovery(const struct exception_table_entry *ex,
> + struct pt_regs *regs, unsigned int esr)
> +{
> + if (esr_is_sea(esr))
> + regs->regs[0] = 0;
> + else
> + regs->regs[0] = 1;
> +
> + regs->pc = get_ex_fixup(ex);
> + return true;
> +}
> +
> static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
> struct pt_regs *regs)
> {
> @@ -63,7 +76,7 @@ ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
> return true;
> }
>
> -bool fixup_exception(struct pt_regs *regs)
> +bool fixup_exception(struct pt_regs *regs, unsigned int esr)
> {
> const struct exception_table_entry *ex;
>
> @@ -71,12 +84,18 @@ bool fixup_exception(struct pt_regs *regs)
> if (!ex)
> return false;
>
> + if (esr_is_sea(esr) && !IS_EX_TYPE_UCE_RECOVERY(ex->type))
> + return false;
> +
> switch (ex->type) {
> case EX_TYPE_FIXUP:
> return ex_handler_fixup(ex, regs);
> + case EX_TYPE_FIXUP_UCE_RECOVERY:
> + return ex_handler_fixup_uce_recovery(ex, regs, esr);
> case EX_TYPE_BPF:
> return ex_handler_bpf(ex, regs);
> case EX_TYPE_UACCESS_ERR_ZERO:
> + case EX_TYPE_UACCESS_ERR_ZERO_UCE_RECOVERY:
> return ex_handler_uaccess_err_zero(ex, regs);
> case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
> return ex_handler_load_unaligned_zeropad(ex, regs);
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 77341b160aca..47c447554d2a 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -361,7 +361,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr,
> * Are we prepared to handle this kernel fault?
> * We are almost certainly not prepared to handle instruction faults.
> */
> - if (!is_el1_instruction_abort(esr) && fixup_exception(regs))
> + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr))
> return;
>
> if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs),
> @@ -695,6 +695,30 @@ static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs)
> return 1; /* "fault" */
> }
>
> +static bool arm64_process_kernel_sea(unsigned long addr, unsigned int esr,
> + struct pt_regs *regs, int sig, int code)
> +{
> + if (!IS_ENABLED(CONFIG_ARM64_UCE_KERNEL_RECOVERY))
> + return false;
> +
> + if (user_mode(regs) || !current->mm)
> + return false;
> +
> + if (apei_claim_sea(regs) < 0)
> + return false;
> +
> + current->thread.fault_address = 0;
> + current->thread.fault_code = esr;
> +
> + if (!fixup_exception(regs, esr))
> + return false;
> +
> + arm64_force_sig_fault(sig, code, addr,
> + "Uncorrected hardware memory error in kernel-access\n");
> +
> + return true;
> +}
Based on X86 RAS implementation[1], I don't think we shoud use arm64_force_sig_fault to
kill process in this case. Instead, we could return -EFAULT in fixup_exception and left
the rest work in memory_failure.
> Sending a SIGBUS for a copy from user is not the correct semantic.
> System calls should return -EFAULT (or a short count for write(2)).
[1]https://lore.kernel.org/all/[email protected]/T/#m6707a73fc8316690818b6e7eea0329b5925e1f9d
Best Regards,
Shuai