SFrame V3 introduces flexible FDEs in addition to the regular FDEs. The key difference is that flexible FDEs encode the CFA, RA, and FP tracking information using two FRE data words, a control word and an offset, or a single padding data word of zero (e.g. to represent FP without RA tracking information).
The control word contains the following information: - reg_p: Whether to use the register contents (reg_p=1) specified by regnum or the CFA (reg_p=0) as base. - deref_p: Whether to dereference. - regnum: A DWARF register number. The offset is added to the base (i.e. CFA or register contents). Then the resulting address may optionally be dereferenced. This enables the following flexible CFA and FP/RA recovery rules: - CFA = register + offset // reg_p=1, deref_p=0 - CFA = *(register + offset) // reg_p=1, deref_p=1 - FP/RA = *(CFA + offset) // reg_p=0, deref_p=0 - FP/RA = register + offset // reg_p=1, deref_p=0 - FP/RA = *(register + offset) // reg_p=1, deref_p=1 Note that for the CFA a rule with reg_p=0 is invalid, as the value of the CFA cannot be described using itself as base. For FP/RA a rule with reg_p=0 and deref_p=0 and regnum=0 is invalid, as it that is equal to the padding data word of zero. Cc: Steven Rostedt <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Andrii Nakryiko <[email protected]> Cc: Indu Bhagat <[email protected]> Cc: "Jose E. Marchesi" <[email protected]> Cc: Beau Belgrave <[email protected]> Cc: Jens Remus <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Florian Weimer <[email protected]> Cc: Sam James <[email protected]> Cc: Kees Cook <[email protected]> Cc: "Carlos O'Donell" <[email protected]> Signed-off-by: Jens Remus <[email protected]> --- Notes (jremus): Changes in v13: - New patch. kernel/unwind/sframe.c | 249 ++++++++++++++++++++++++++++++++--------- kernel/unwind/sframe.h | 5 + 2 files changed, 204 insertions(+), 50 deletions(-) diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c index 4dfc8cf2075e..ebf2a2905c5c 100644 --- a/kernel/unwind/sframe.c +++ b/kernel/unwind/sframe.c @@ -12,6 +12,7 @@ #include <linux/mm.h> #include <linux/string_helpers.h> #include <linux/sframe.h> +#include <asm/unwind_user_sframe.h> #include <linux/unwind_user_types.h> #include "sframe.h" @@ -31,8 +32,11 @@ struct sframe_fde_internal { struct sframe_fre_internal { unsigned int size; u32 ip_off; + u32 cfa_ctl; s32 cfa_off; + u32 ra_ctl; s32 ra_off; + u32 fp_ctl; s32 fp_off; u8 info; }; @@ -189,16 +193,147 @@ static __always_inline int __find_fde(struct sframe_section *sec, s32 : UNSAFE_GET_USER_SIGNED_INC(to, from, size, label), \ s64 : UNSAFE_GET_USER_SIGNED_INC(to, from, size, label)) +static __always_inline int +__read_regular_fre_datawords(struct sframe_section *sec, + struct sframe_fde_internal *fde, + unsigned long cur, + unsigned char dataword_count, + unsigned char dataword_size, + struct sframe_fre_internal *fre) +{ + s32 cfa_off, ra_off, fp_off; + unsigned int cfa_regnum; + + UNSAFE_GET_USER_INC(cfa_off, cur, dataword_size, Efault); + dataword_count--; + + ra_off = sec->ra_off; + if (!ra_off && dataword_count) { + dataword_count--; + UNSAFE_GET_USER_INC(ra_off, cur, dataword_size, Efault); + } + + fp_off = sec->fp_off; + if (!fp_off && dataword_count) { + dataword_count--; + UNSAFE_GET_USER_INC(fp_off, cur, dataword_size, Efault); + } + + if (dataword_count) + return -EFAULT; + + cfa_regnum = + (SFRAME_V3_FRE_CFA_BASE_REG_ID(fre->info) == SFRAME_BASE_REG_FP) ? + SFRAME_REG_FP : SFRAME_REG_SP; + + fre->cfa_ctl = (cfa_regnum << 3) | 1; /* regnum, deref_p=0, reg_p=1 */ + fre->cfa_off = cfa_off; + fre->ra_ctl = ra_off ? 2 : 0; /* regnum=0, deref_p=(ra_off != 0), reg_p=0 */ + fre->ra_off = ra_off; + fre->fp_ctl = fp_off ? 2 : 0; /* regnum=0, deref_p=(fp_off != 0), reg_p=0 */ + fre->fp_off = fp_off; + + return 0; + +Efault: + return -EFAULT; +} + +static __always_inline int +__read_flex_fde_fre_datawords(struct sframe_section *sec, + struct sframe_fde_internal *fde, + unsigned long cur, + unsigned char dataword_count, + unsigned char dataword_size, + struct sframe_fre_internal *fre) +{ + u32 cfa_ctl, ra_ctl, fp_ctl; + s32 cfa_off, ra_off, fp_off; + + if (dataword_count < 2) + return -EFAULT; + UNSAFE_GET_USER_INC(cfa_ctl, cur, dataword_size, Efault); + UNSAFE_GET_USER_INC(cfa_off, cur, dataword_size, Efault); + dataword_count -= 2; + + ra_off = sec->ra_off; + ra_ctl = ra_off ? 2 : 0; /* regnum=0, deref_p=(ra_off != 0), reg_p=0 */ + if (dataword_count >= 2) { + UNSAFE_GET_USER_INC(ra_ctl, cur, dataword_size, Efault); + dataword_count--; + if (ra_ctl) { + UNSAFE_GET_USER_INC(ra_off, cur, dataword_size, Efault); + dataword_count--; + } else { + /* Padding RA location info */ + ra_ctl = ra_off ? 2 : 0; /* re-deduce (see above) */ + } + } + + fp_off = sec->fp_off; + fp_ctl = fp_off ? 2 : 0; /* regnum=0, deref_p=(fp_off != 0), reg_p=0 */ + if (dataword_count >= 2) { + UNSAFE_GET_USER_INC(fp_ctl, cur, dataword_size, Efault); + dataword_count--; + if (fp_ctl) { + UNSAFE_GET_USER_INC(fp_off, cur, dataword_size, Efault); + dataword_count--; + } else { + /* Padding FP location info */ + fp_ctl = fp_off ? 2 : 0; /* re-deduce (see above) */ + } + } + + if (dataword_count) + return -EFAULT; + + fre->cfa_ctl = cfa_ctl; + fre->cfa_off = cfa_off; + fre->ra_ctl = ra_ctl; + fre->ra_off = ra_off; + fre->fp_ctl = fp_ctl; + fre->fp_off = fp_off; + + return 0; + +Efault: + return -EFAULT; +} + +static __always_inline int +__read_fre_datawords(struct sframe_section *sec, + struct sframe_fde_internal *fde, + unsigned long cur, + unsigned char dataword_count, + unsigned char dataword_size, + struct sframe_fre_internal *fre) +{ + unsigned char fde_type = SFRAME_V3_FDE_TYPE(fde->info2); + + switch (fde_type) { + case SFRAME_FDE_TYPE_REGULAR: + return __read_regular_fre_datawords(sec, fde, cur, + dataword_count, + dataword_size, + fre); + case SFRAME_FDE_TYPE_FLEXIBLE: + return __read_flex_fde_fre_datawords(sec, fde, cur, + dataword_count, + dataword_size, + fre); + default: + return -EFAULT; + } +} + static __always_inline int __read_fre(struct sframe_section *sec, struct sframe_fde_internal *fde, unsigned long fre_addr, struct sframe_fre_internal *fre) { - unsigned char fde_type = SFRAME_V3_FDE_TYPE(fde->info2); unsigned char fde_pctype = SFRAME_V3_FDE_PCTYPE(fde->info); unsigned char fre_type = SFRAME_V3_FDE_FRE_TYPE(fde->info); unsigned char dataword_count, dataword_size; - s32 cfa_off, ra_off, fp_off; unsigned long cur = fre_addr; unsigned char addr_size; u32 ip_off; @@ -224,75 +359,88 @@ static __always_inline int __read_fre(struct sframe_section *sec, if (cur + (dataword_count * dataword_size) > sec->fres_end) return -EFAULT; - /* TODO: Support for flexible FDEs not implemented yet. */ - if (fde_type != SFRAME_FDE_TYPE_REGULAR) - return -EFAULT; + fre->size = addr_size + 1 + (dataword_count * dataword_size); + fre->ip_off = ip_off; + fre->info = info; if (!dataword_count) { /* * A FRE without data words indicates RA undefined / * outermost frame. */ - cfa_off = 0; - ra_off = 0; - fp_off = 0; - goto done; - } + fre->cfa_ctl = 0; + fre->cfa_off = 0; + fre->ra_ctl = 0; + fre->ra_off = 0; + fre->fp_ctl = 0; + fre->fp_off = 0; - UNSAFE_GET_USER_INC(cfa_off, cur, dataword_size, Efault); - dataword_count--; - - ra_off = sec->ra_off; - if (!ra_off && dataword_count) { - dataword_count--; - UNSAFE_GET_USER_INC(ra_off, cur, dataword_size, Efault); - } - - fp_off = sec->fp_off; - if (!fp_off && dataword_count) { - dataword_count--; - UNSAFE_GET_USER_INC(fp_off, cur, dataword_size, Efault); + return 0; } - if (dataword_count) - return -EFAULT; - -done: - fre->size = addr_size + 1 + (dataword_count * dataword_size); - fre->ip_off = ip_off; - fre->cfa_off = cfa_off; - fre->ra_off = ra_off; - fre->fp_off = fp_off; - fre->info = info; - - return 0; + return __read_fre_datawords(sec, fde, cur, dataword_count, dataword_size, fre); Efault: return -EFAULT; } -static __always_inline void +static __always_inline int sframe_init_cfa_rule_data(struct unwind_user_cfa_rule_data *cfa_rule_data, - unsigned char fre_info, - s32 offset) + u32 ctlword, s32 offset) { - if (SFRAME_V3_FRE_CFA_BASE_REG_ID(fre_info) == SFRAME_BASE_REG_FP) - cfa_rule_data->rule = UNWIND_USER_CFA_RULE_FP_OFFSET; - else - cfa_rule_data->rule = UNWIND_USER_CFA_RULE_SP_OFFSET; + bool deref_p = SFRAME_V3_FLEX_FDE_CTLWORD_DEREF_P(ctlword); + bool reg_p = SFRAME_V3_FLEX_FDE_CTLWORD_REG_P(ctlword); + + if (reg_p) { + unsigned int regnum = SFRAME_V3_FLEX_FDE_CTLWORD_REGNUM(ctlword); + + switch (regnum) { + case SFRAME_REG_SP: + cfa_rule_data->rule = UNWIND_USER_CFA_RULE_SP_OFFSET; + break; + case SFRAME_REG_FP: + cfa_rule_data->rule = UNWIND_USER_CFA_RULE_FP_OFFSET; + break; + default: + cfa_rule_data->rule = UNWIND_USER_CFA_RULE_REG_OFFSET; + cfa_rule_data->regnum = regnum; + } + } else { + return -EINVAL; + } + + if (deref_p) + cfa_rule_data->rule |= UNWIND_USER_RULE_DEREF; + cfa_rule_data->offset = offset; + + return 0; } static __always_inline void sframe_init_rule_data(struct unwind_user_rule_data *rule_data, - s32 offset) + u32 ctlword, s32 offset) { - if (offset) { - rule_data->rule = UNWIND_USER_RULE_CFA_OFFSET_DEREF; - rule_data->offset = offset; - } else { + bool deref_p = SFRAME_V3_FLEX_FDE_CTLWORD_DEREF_P(ctlword); + bool reg_p = SFRAME_V3_FLEX_FDE_CTLWORD_REG_P(ctlword); + + if (!ctlword && !offset) { rule_data->rule = UNWIND_USER_RULE_RETAIN; + return; + } + if (reg_p) { + unsigned int regnum = SFRAME_V3_FLEX_FDE_CTLWORD_REGNUM(ctlword); + + rule_data->rule = UNWIND_USER_RULE_REG_OFFSET; + rule_data->regnum = regnum; + } else { + rule_data->rule = UNWIND_USER_RULE_CFA_OFFSET; } + + if (deref_p) + rule_data->rule |= UNWIND_USER_RULE_DEREF; + + rule_data->offset = offset; } static __always_inline int __find_fre(struct sframe_section *sec, @@ -344,9 +492,10 @@ static __always_inline int __find_fre(struct sframe_section *sec, return -EINVAL; fre = prev_fre; - sframe_init_cfa_rule_data(&frame->cfa, fre->info, fre->cfa_off); - sframe_init_rule_data(&frame->ra, fre->ra_off); - sframe_init_rule_data(&frame->fp, fre->fp_off); + if (sframe_init_cfa_rule_data(&frame->cfa, fre->cfa_ctl, fre->cfa_off)) + return -EINVAL; + sframe_init_rule_data(&frame->ra, fre->ra_ctl, fre->ra_off); + sframe_init_rule_data(&frame->fp, fre->fp_ctl, fre->fp_off); frame->outermost = SFRAME_V3_FRE_RA_UNDEFINED_P(fre->info); return 0; diff --git a/kernel/unwind/sframe.h b/kernel/unwind/sframe.h index 3fcc15534e5a..5b6112945b6c 100644 --- a/kernel/unwind/sframe.h +++ b/kernel/unwind/sframe.h @@ -66,6 +66,7 @@ struct sframe_fda_v3 { #define SFRAME_V3_AARCH64_FDE_PAUTH_KEY(info) (((info) >> 5) & 0x1) #define SFRAME_FDE_TYPE_REGULAR 0 +#define SFRAME_FDE_TYPE_FLEXIBLE 1 #define SFRAME_V3_FDE_TYPE_MASK 0x0f #define SFRAME_V3_FDE_TYPE(info2) ((info2) & SFRAME_V3_FDE_TYPE_MASK) @@ -79,4 +80,8 @@ struct sframe_fda_v3 { #define SFRAME_V3_AARCH64_FRE_MANGLED_RA_P(info) (((info) >> 7) & 0x1) #define SFRAME_V3_FRE_RA_UNDEFINED_P(info) (SFRAME_V3_FRE_DATAWORD_COUNT(info) == 0) +#define SFRAME_V3_FLEX_FDE_CTLWORD_REGNUM(data) (((data) >> 3) & 0x1f) +#define SFRAME_V3_FLEX_FDE_CTLWORD_DEREF_P(data) (((data) >> 1) & 0x1) +#define SFRAME_V3_FLEX_FDE_CTLWORD_REG_P(data) ((data) & 0x1) + #endif /* _SFRAME_H */ -- 2.51.0
