From d6e2cc56477538255160ed02fdb11b0da60356cc Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 19 Oct 2021 17:02:16 +0100 Subject: arm64: extable: add `type` and `data` fields Subsequent patches will add specialized handlers for fixups, in addition to the simple PC fixup and BPF handlers we have today. In preparation, this patch adds a new `type` field to struct exception_table_entry, and uses this to distinguish the fixup and BPF cases. A `data` field is also added so that subsequent patches can associate data specific to each exception site (e.g. register numbers). Handlers are named ex_handler_*() for consistency, following the exmaple of x86. At the same time, get_ex_fixup() is split out into a helper so that it can be used by other ex_handler_*() functions ins subsequent patches. This patch will increase the size of the exception tables, which will be remedied by subsequent patches removing redundant fixup code. There should be no functional change as a result of this patch. Since each entry is now 12 bytes in size, we must reduce the alignment of each entry from `.align 3` (i.e. 8 bytes) to `.align 2` (i.e. 4 bytes), which is the natrual alignment of the `insn` and `fixup` fields. The current 8-byte alignment is a holdover from when the `insn` and `fixup` fields was 8 bytes, and while not harmful has not been necessary since commit: 6c94f27ac847ff8e ("arm64: switch to relative exception tables") Similarly, RO_EXCEPTION_TABLE_ALIGN is dropped to 4 bytes. Concurrently with this patch, x86's exception table entry format is being updated (similarly to a 12-byte format, with 32-bytes of absolute data). Once both have been merged it should be possible to unify the sorttable logic for the two. Signed-off-by: Mark Rutland Reviewed-by: Ard Biesheuvel Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Catalin Marinas Cc: Daniel Borkmann Cc: James Morse Cc: Jean-Philippe Brucker Cc: Robin Murphy Cc: Will Deacon Link: https://lore.kernel.org/r/20211019160219.5202-11-mark.rutland@arm.com Signed-off-by: Will Deacon --- arch/arm64/mm/extable.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) (limited to 'arch/arm64/mm/extable.c') diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index dba3d59f3eca..c2951b963335 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -6,6 +6,24 @@ #include #include +#include + +typedef bool (*ex_handler_t)(const struct exception_table_entry *, + struct pt_regs *); + +static inline unsigned long +get_ex_fixup(const struct exception_table_entry *ex) +{ + return ((unsigned long)&ex->fixup + ex->fixup); +} + +static bool ex_handler_fixup(const struct exception_table_entry *ex, + struct pt_regs *regs) +{ + regs->pc = get_ex_fixup(ex); + return true; +} + bool fixup_exception(struct pt_regs *regs) { const struct exception_table_entry *ex; @@ -14,9 +32,12 @@ bool fixup_exception(struct pt_regs *regs) if (!ex) return false; - if (in_bpf_jit(regs)) - return arm64_bpf_fixup_exception(ex, regs); + switch (ex->type) { + case EX_TYPE_FIXUP: + return ex_handler_fixup(ex, regs); + case EX_TYPE_BPF: + return ex_handler_bpf(ex, regs); + } - regs->pc = (unsigned long)&ex->fixup + ex->fixup; - return true; + BUG(); } -- cgit v1.2.3