From: Josh Poimboeuf <jpoim...@kernel.org> Add optional support for user space frame pointer unwinding. If supported, the arch needs to enable CONFIG_HAVE_UNWIND_USER_FP and define ARCH_INIT_USER_FP_FRAME.
By encoding the frame offsets in struct unwind_user_frame, much of this code can also be reused for future unwinder implementations like sframe. Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org> Co-developed-by: Steven Rostedt (Google) <rost...@goodmis.org> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> --- Changes since v12: https://lore.kernel.org/20250701005450.888492...@goodmis.org - Added test when use_fp is true to make sure fp < sp (Jens Remus) - Make sure the address read is word aligned (Linus Torvalds) arch/Kconfig | 4 ++ include/asm-generic/Kbuild | 1 + include/asm-generic/unwind_user.h | 5 +++ include/linux/unwind_user.h | 5 +++ include/linux/unwind_user_types.h | 1 + kernel/unwind/user.c | 65 ++++++++++++++++++++++++++++++- 6 files changed, 79 insertions(+), 2 deletions(-) create mode 100644 include/asm-generic/unwind_user.h diff --git a/arch/Kconfig b/arch/Kconfig index ea59e5d7cc69..8e3fd723bd74 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -438,6 +438,10 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH config UNWIND_USER bool +config HAVE_UNWIND_USER_FP + bool + select UNWIND_USER + config HAVE_PERF_REGS bool help diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild index 8675b7b4ad23..295c94a3ccc1 100644 --- a/include/asm-generic/Kbuild +++ b/include/asm-generic/Kbuild @@ -59,6 +59,7 @@ mandatory-y += tlbflush.h mandatory-y += topology.h mandatory-y += trace_clock.h mandatory-y += uaccess.h +mandatory-y += unwind_user.h mandatory-y += vermagic.h mandatory-y += vga.h mandatory-y += video.h diff --git a/include/asm-generic/unwind_user.h b/include/asm-generic/unwind_user.h new file mode 100644 index 000000000000..b8882b909944 --- /dev/null +++ b/include/asm-generic/unwind_user.h @@ -0,0 +1,5 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_UNWIND_USER_H +#define _ASM_GENERIC_UNWIND_USER_H + +#endif /* _ASM_GENERIC_UNWIND_USER_H */ diff --git a/include/linux/unwind_user.h b/include/linux/unwind_user.h index 1d77bed8de2c..7f7282516bf5 100644 --- a/include/linux/unwind_user.h +++ b/include/linux/unwind_user.h @@ -3,6 +3,11 @@ #define _LINUX_UNWIND_USER_H #include <linux/unwind_user_types.h> +#include <asm/unwind_user.h> + +#ifndef ARCH_INIT_USER_FP_FRAME + #define ARCH_INIT_USER_FP_FRAME +#endif int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries); diff --git a/include/linux/unwind_user_types.h b/include/linux/unwind_user_types.h index 6ed1b4ae74e1..65bd070eb6b0 100644 --- a/include/linux/unwind_user_types.h +++ b/include/linux/unwind_user_types.h @@ -6,6 +6,7 @@ enum unwind_user_type { UNWIND_USER_TYPE_NONE, + UNWIND_USER_TYPE_FP, }; struct unwind_stacktrace { diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c index d0cf3ee2706d..62b3ef37d71b 100644 --- a/kernel/unwind/user.c +++ b/kernel/unwind/user.c @@ -6,13 +6,71 @@ #include <linux/sched.h> #include <linux/sched/task_stack.h> #include <linux/unwind_user.h> +#include <linux/uaccess.h> + +static struct unwind_user_frame fp_frame = { + ARCH_INIT_USER_FP_FRAME +}; + +static inline bool fp_state(struct unwind_user_state *state) +{ + return IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP) && + state->type == UNWIND_USER_TYPE_FP; +} #define for_each_user_frame(state) \ for (unwind_user_start(state); !(state)->done; unwind_user_next(state)) static int unwind_user_next(struct unwind_user_state *state) { - /* no implementation yet */ + struct unwind_user_frame *frame; + unsigned long cfa = 0, fp, ra = 0; + unsigned int shift; + + if (state->done) + return -EINVAL; + + if (fp_state(state)) + frame = &fp_frame; + else + goto done; + + if (frame->use_fp) { + if (state->fp < state->sp) + goto done; + cfa = state->fp; + } else { + cfa = state->sp; + } + + /* Get the Canonical Frame Address (CFA) */ + cfa += frame->cfa_off; + + /* stack going in wrong direction? */ + if (cfa <= state->sp) + goto done; + + /* Make sure that the address is word aligned */ + shift = sizeof(long) == 4 ? 2 : 3; + if ((cfa + frame->ra_off) & ((1 << shift) - 1)) + goto done; + + /* Find the Return Address (RA) */ + if (get_user(ra, (unsigned long *)(cfa + frame->ra_off))) + goto done; + + if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off))) + goto done; + + state->ip = ra; + state->sp = cfa; + if (frame->fp_off) + state->fp = fp; + + return 0; + +done: + state->done = true; return -EINVAL; } @@ -27,7 +85,10 @@ static int unwind_user_start(struct unwind_user_state *state) return -EINVAL; } - state->type = UNWIND_USER_TYPE_NONE; + if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP)) + state->type = UNWIND_USER_TYPE_FP; + else + state->type = UNWIND_USER_TYPE_NONE; state->ip = instruction_pointer(regs); state->sp = user_stack_pointer(regs); -- 2.47.2
