Enable architectures to handle DWARF expressions in DWARF CFI instructions DW_CFA_def_cfa_expression, DW_CFA_expression, and DW_CFA_val_expression. Limit the maximum expression length to a reasonable size, while enabling architectures to override the limit.
Architectures are supposed to only handle specific known expressions or expression patterns, not to implement a stack-based expression evaluation machinery. Signed-off-by: Jens Remus <[email protected]> --- include/asm-generic/unwind_user_eh_frame.h | 41 +++++++++++++ include/linux/unwind_user_eh_frame_types.h | 37 ++++++++++++ kernel/unwind/eh_frame.c | 70 +++++++++++----------- 3 files changed, 113 insertions(+), 35 deletions(-) create mode 100644 include/linux/unwind_user_eh_frame_types.h diff --git a/include/asm-generic/unwind_user_eh_frame.h b/include/asm-generic/unwind_user_eh_frame.h index e6d207597206..da9bc52a645a 100644 --- a/include/asm-generic/unwind_user_eh_frame.h +++ b/include/asm-generic/unwind_user_eh_frame.h @@ -2,6 +2,8 @@ #ifndef _ASM_GENERIC_UNWIND_USER_EH_FRAME_H #define _ASM_GENERIC_UNWIND_USER_EH_FRAME_H +#include <linux/unwind_user_eh_frame_types.h> + #ifndef EH_FRAME_MAX_CIE_LENGTH #define EH_FRAME_MAX_CIE_LENGTH 128 #endif @@ -10,6 +12,10 @@ #define EH_FRAME_MAX_AUGSTR_LENGTH 16 #endif +#ifndef EH_FRAME_MAX_EXPRESSION_LENGTH +#define EH_FRAME_MAX_EXPRESSION_LENGTH 32 +#endif + #ifndef EH_FRAME_MAX_STATE_STACK #define EH_FRAME_MAX_STATE_STACK 8 #endif @@ -39,5 +45,40 @@ static inline bool eh_frame_reject_sp_rule(void) #define eh_frame_reject_sp_rule eh_frame_reject_sp_rule #endif +#ifndef eh_frame_do_def_cfa_expression +static inline int eh_frame_do_def_cfa_expression(const char *expr, + int size, + unsigned long ip, + struct eh_frame_reg_state *reg_state) +{ + return -EOPNOTSUPP; +} +#define eh_frame_do_def_cfa_expression eh_frame_do_def_cfa_expression +#endif + +#ifndef eh_frame_do_expression +static inline int eh_frame_do_expression(unsigned int reg, + const char *expr, + int size, + unsigned long ip, + struct eh_frame_reg_state *reg_state) +{ + return -EOPNOTSUPP; +} +#define eh_frame_do_expression eh_frame_do_expression +#endif + +#ifndef eh_frame_do_val_expression +static inline int eh_frame_do_val_expression(unsigned int reg, + const char *expr, + int size, + unsigned long ip, + struct eh_frame_reg_state *reg_state) +{ + return -EOPNOTSUPP; +} +#define eh_frame_do_val_expression eh_frame_do_val_expression +#endif + #endif /* _ASM_GENERIC_UNWIND_USER_EH_FRAME_H */ diff --git a/include/linux/unwind_user_eh_frame_types.h b/include/linux/unwind_user_eh_frame_types.h new file mode 100644 index 000000000000..e9f9d1abb76f --- /dev/null +++ b/include/linux/unwind_user_eh_frame_types.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_UNWIND_USER_EH_FRAME_TYPES_H +#define _LINUX_UNWIND_USER_EH_FRAME_TYPES_H + +enum eh_frame_cfa_rule { + CFA_UNDEFINED, /* unrecoverable */ + CFA_REG_OFFSET, /* CFA = reg + offset */ +}; + +enum eh_frame_reg_rule { + REG_UNDEFINED_IMPLICIT, /* reg = reg */ + REG_UNDEFINED_EXPLICIT, /* unrecoverable; RA: outermost frame */ + REG_SAME_VALUE, /* reg = reg; TODO: reset to CIE initial CFI */ + REG_OFFSET, /* reg = *(CFA + offset) */ + REG_VAL_OFFSET, /* reg = CFA + offset */ + REG_REGISTER, /* reg = other_reg */ +}; + +enum eh_frame_reg_index { + FP_IDX, /* frame pointer (FP) */ + RA_IDX, /* return address (RA) */ + NR_REGS +}; + +struct eh_frame_reg_state { + /* CFA recovery rule */ + enum eh_frame_cfa_rule cfa_rule; + unsigned long cfa_regnum; + long cfa_offset; + + /* FP and RA recovery rules (SP uses implicit recovery) */ + enum eh_frame_reg_rule reg_rule[NR_REGS]; + unsigned long reg_regnum[NR_REGS]; + long reg_offset[NR_REGS]; +}; + +#endif /* _LINUX_UNWIND_USER_EH_FRAME_TYPES_H */ diff --git a/kernel/unwind/eh_frame.c b/kernel/unwind/eh_frame.c index 64176242b7d8..f7f1234b0437 100644 --- a/kernel/unwind/eh_frame.c +++ b/kernel/unwind/eh_frame.c @@ -12,45 +12,14 @@ #include <linux/mm.h> #include <linux/string_helpers.h> #include <linux/eh_frame.h> +#include <linux/types.h> #include <linux/unwind_user_types.h> +#include <linux/unwind_user_eh_frame_types.h> #include <asm/unwind_user_eh_frame.h> #include "eh_frame.h" #include "eh_frame_debug.h" -/* Register state for CFI interpreter */ -enum eh_frame_cfa_rule { - CFA_UNDEFINED, /* unrecoverable */ - CFA_REG_OFFSET, /* CFA = reg + offset */ -}; - -enum eh_frame_reg_rule { - REG_UNDEFINED_IMPLICIT, /* reg = reg */ - REG_UNDEFINED_EXPLICIT, /* unrecoverable; RA: outermost frame */ - REG_SAME_VALUE, /* reg = reg; TODO: reset to CIE initial CFI */ - REG_OFFSET, /* reg = *(CFA + offset) */ - REG_VAL_OFFSET, /* reg = CFA + offset */ - REG_REGISTER, /* reg = other_reg */ -}; - -enum eh_frame_reg_index { - FP_IDX, /* frame pointer (FP) */ - RA_IDX, /* return address (RA) */ - NR_REGS -}; - -struct eh_frame_reg_state { - /* CFA recovery rule */ - enum eh_frame_cfa_rule cfa_rule; - unsigned long cfa_regnum; - long cfa_offset; - - /* FP and RA recovery rules (SP uses implicit recovery) */ - enum eh_frame_reg_rule reg_rule[NR_REGS]; - unsigned long reg_regnum[NR_REGS]; - long reg_offset[NR_REGS]; -}; - struct eh_frame_cfi_context { struct eh_frame_reg_state state; struct eh_frame_reg_state stack[EH_FRAME_MAX_STATE_STACK]; @@ -839,6 +808,27 @@ static __always_inline int __do_cfi_insn(struct eh_frame_section *sec, break; } + case DW_CFA_def_cfa_expression: { + unsigned long expr_len; + char expr[EH_FRAME_MAX_EXPRESSION_LENGTH]; + + ret = read_uleb128(&cur, end, &expr_len); + if (ret) + return ret; + + if (cur + expr_len > end) + return -EINVAL; + + if (expr_len > sizeof(expr)) + return -EOPNOTSUPP; + unsafe_copy_from_user(&expr, (void __user *)cur, expr_len, Efault); + ret = eh_frame_do_def_cfa_expression(expr, expr_len, target_ip, &ctx->state); + if (ret) + return ret; + cur += expr_len; + break; + } + case DW_CFA_undefined: { unsigned long reg; int idx; @@ -1005,9 +995,19 @@ static __always_inline int __do_cfi_insn(struct eh_frame_section *sec, if (cur + expr_len > end) return -EINVAL; - if (reg == EH_FRAME_REG_SP || reg == EH_FRAME_REG_FP || reg == EH_FRAME_REG_RA) - return -EOPNOTSUPP; + if (reg == EH_FRAME_REG_SP || reg == EH_FRAME_REG_FP || reg == EH_FRAME_REG_RA) { + char expr[EH_FRAME_MAX_EXPRESSION_LENGTH]; + if (expr_len > sizeof(expr)) + return -EOPNOTSUPP; + unsafe_copy_from_user(&expr, (void __user *)cur, expr_len, Efault); + if (opcode == DW_CFA_expression) + ret = eh_frame_do_expression(reg, expr, expr_len, target_ip, &ctx->state); + else + ret = eh_frame_do_val_expression(reg, expr, expr_len, target_ip, &ctx->state); + if (ret) + return ret; + } cur += expr_len; break; } -- 2.53.0
