kernel.git/arch/arm64/kernel/kgdb.c, branch linux-4.9.y

arm64: kgdb: Fix single-step exception handling oops

2020-07-22T07:10:45Z

[ Upstream commit 8523c006264df65aac7d77284cc69aac46a6f842 ] After entering kdb due to breakpoint, when we execute 'ss' or 'go' (will delay installing breakpoints, do single-step first), it won't work correctly, and it will enter kdb due to oops. It's because the reason gotten in kdb_stub() is not as expected, and it seems that the ex_vector for single-step should be 0, like what arch powerpc/sh/parisc has implemented. Before the patch: Entering kdb (current=0xffff8000119e2dc0, pid 0) on processor 0 due to Keyboard Entry [0]kdb> bp printk Instruction(i) BP #0 at 0xffff8000101486cc (printk) is enabled addr at ffff8000101486cc, hardtype=0 installed=0 [0]kdb> g / # echo h > /proc/sysrq-trigger Entering kdb (current=0xffff0000fa878040, pid 266) on processor 3 due to Breakpoint @ 0xffff8000101486cc [3]kdb> ss Entering kdb (current=0xffff0000fa878040, pid 266) on processor 3 Oops: (null) due to oops @ 0xffff800010082ab8 CPU: 3 PID: 266 Comm: sh Not tainted 5.7.0-rc4-13839-gf0e5ad491718 #6 Hardware name: linux,dummy-virt (DT) pstate: 00000085 (nzcv daIf -PAN -UAO) pc : el1_irq+0x78/0x180 lr : __handle_sysrq+0x80/0x190 sp : ffff800015003bf0 x29: ffff800015003d20 x28: ffff0000fa878040 x27: 0000000000000000 x26: ffff80001126b1f0 x25: ffff800011b6a0d8 x24: 0000000000000000 x23: 0000000080200005 x22: ffff8000101486cc x21: ffff800015003d30 x20: 0000ffffffffffff x19: ffff8000119f2000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000 x8 : ffff800015003e50 x7 : 0000000000000002 x6 : 00000000380b9990 x5 : ffff8000106e99e8 x4 : ffff0000fadd83c0 x3 : 0000ffffffffffff x2 : ffff800011b6a0d8 x1 : ffff800011b6a000 x0 : ffff80001130c9d8 Call trace: el1_irq+0x78/0x180 printk+0x0/0x84 write_sysrq_trigger+0xb0/0x118 proc_reg_write+0xb4/0xe0 __vfs_write+0x18/0x40 vfs_write+0xb0/0x1b8 ksys_write+0x64/0xf0 __arm64_sys_write+0x14/0x20 el0_svc_common.constprop.2+0xb0/0x168 do_el0_svc+0x20/0x98 el0_sync_handler+0xec/0x1a8 el0_sync+0x140/0x180 [3]kdb> After the patch: Entering kdb (current=0xffff8000119e2dc0, pid 0) on processor 0 due to Keyboard Entry [0]kdb> bp printk Instruction(i) BP #0 at 0xffff8000101486cc (printk) is enabled addr at ffff8000101486cc, hardtype=0 installed=0 [0]kdb> g / # echo h > /proc/sysrq-trigger Entering kdb (current=0xffff0000fa852bc0, pid 268) on processor 0 due to Breakpoint @ 0xffff8000101486cc [0]kdb> g Entering kdb (current=0xffff0000fa852bc0, pid 268) on processor 0 due to Breakpoint @ 0xffff8000101486cc [0]kdb> ss Entering kdb (current=0xffff0000fa852bc0, pid 268) on processor 0 due to SS trap @ 0xffff800010082ab8 [0]kdb> Fixes: 44679a4f142b ("arm64: KGDB: Add step debugging support") Signed-off-by: Wei Li Tested-by: Douglas Anderson Reviewed-by: Douglas Anderson Link: https://lore.kernel.org/r/20200509214159.19680-2-liwei391@huawei.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64: debug: Ensure debug handlers check triggering exception level

2019-04-05T20:29:03Z

commit 6bd288569b50bc89fa5513031086746968f585cb upstream. Debug exception handlers may be called for exceptions generated both by user and kernel code. In many cases, this is checked explicitly, but in other cases things either happen to work by happy accident or they go slightly wrong. For example, executing 'brk #4' from userspace will enter the kprobes code and be ignored, but the instruction will be retried forever in userspace instead of delivering a SIGTRAP. Fix this issue in the most stable-friendly fashion by simply adding explicit checks of the triggering exception level to all of our debug exception handlers. Cc: Reviewed-by: Mark Rutland Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman

arm64: kgdb: handle read-only text / modules

2016-09-23T10:25:01Z

Handle read-only cases when CONFIG_DEBUG_RODATA (4.0) or CONFIG_DEBUG_SET_MODULE_RONX (3.18) are enabled by using aarch64_insn_write() instead of probe_kernel_write() as introduced by commit 2f896d586610 ("arm64: use fixmap for text patching") in 4.0. Fixes: 11d91a770f1f ("arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support") Signed-off-by: AKASHI Takahiro Reviewed-by: Mark Rutland Cc: Will Deacon Cc: Jason Wessel Signed-off-by: Catalin Marinas

arm64: Blacklist non-kprobe-able symbol

2016-07-19T14:03:20Z

Add all function symbols which are called from do_debug_exception under NOKPROBE_SYMBOL, as they can not kprobed. Signed-off-by: Pratyush Anand Acked-by: Masami Hiramatsu Signed-off-by: Catalin Marinas

arm64: kgdb: Match pstate size with gdbserver protocol

2016-06-16T18:20:51Z

Current versions of gdb do not interoperate cleanly with kgdb on arm64 systems because gdb and kgdb do not use the same register description. This patch modifies kgdb to work with recent releases of gdb (>= 7.8.1). Compatibility with gdb (after the patch is applied) is as follows: gdb-7.6 and earlier Ok gdb-7.7 series Works if user provides custom target description gdb-7.8(.0) Works if user provides custom target description gdb-7.8.1 and later Ok When commit 44679a4f142b ("arm64: KGDB: Add step debugging support") was introduced it was paired with a gdb patch that made an incompatible change to the gdbserver protocol. This patch was eventually merged into the gdb sources: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=a4d9ba85ec5597a6a556afe26b712e878374b9dd The change to the protocol was mostly made to simplify big-endian support inside the kernel gdb stub. Unfortunately the gdb project released gdb-7.7.x and gdb-7.8.0 before the protocol incompatibility was identified and reversed: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=bdc144174bcb11e808b4e73089b850cf9620a7ee This leaves us in a position where kgdb still uses the no-longer-used protocol; gdb-7.8.1, which restored the original behaviour, was released on 2014-10-29. I don't believe it is possible to detect/correct the protocol incompatiblity which means the kernel must take a view about which version of the gdb remote protocol is "correct". This patch takes the view that the original/current version of the protocol is correct and that version found in gdb-7.7.x and gdb-7.8.0 is anomalous. Signed-off-by: Daniel Thompson Signed-off-by: Will Deacon

arm64: Fix misspellings in comments.

2016-03-04T18:19:17Z

Signed-off-by: Adam Buchbinder Signed-off-by: Catalin Marinas

arm64/debug: Simplify BRK insn opcode declarations

2015-07-27T10:08:42Z

The way the KGDB_DYN_BRK_INS_BYTEx macros are declared is more complex than it needs to be. Also, the macros are only used in one place, which is arch-specific anyway. This patch refactors the macros to simplify them, and exposes an argument so that we can have a single macro instead of 4. As a side effect, this patch also fixes some anomalous spellings of "KGDB". These changes alter the compile types of some integer constants that are harmless but trigger truncation warnings in gcc when assigning to 32-bit variables. This patch adds an explicit cast for the affected cases. Signed-off-by: Dave Martin Signed-off-by: Will Deacon

arm64/debug: More consistent naming for the BRK ESR template macro

2015-07-27T10:08:42Z

The naming of DBG_ESR_VAL_BRK is inconsistent with the way other similar macros are named. This patch makes the naming more consistent, and appends "64" as a reminder that this ESR pattern only matches from AArch64 state. Signed-off-by: Dave Martin Acked-by: Mark Rutland Acked-by: Catalin Marinas Signed-off-by: Will Deacon

arm64: Fix typos in KGDB macros

2014-09-25T14:35:41Z

Some of the KGDB macros used for generating the BRK instructions had the wrong spelling for DBG and KGDB abbreviations. Signed-off-by: Catalin Marinas

arm64: KGDB: Add step debugging support

2014-02-26T11:16:25Z

Add KGDB software step debugging support for EL1 debug in AArch64 mode. KGDB registers step debug handler with debug monitor. On receiving 'step' command from GDB tool, target enables software step debugging and step address is updated in ELR. Software Step debugging is disabled when 'continue' command is received Signed-off-by: Vijaya Kumar K Reviewed-by: Will Deacon Signed-off-by: Catalin Marinas