From: Christophe Leroy christophe.leroy@c-s.fr
[ Upstream commit fb978ca207743badfe7efd9eebe68bcbb4969f79 ]
Generic implementation fails to remove breakpoints after init when CONFIG_STRICT_KERNEL_RWX is selected:
[ 13.251285] KGDB: BP remove failed: c001c338 [ 13.259587] kgdbts: ERROR PUT: end of test buffer on 'do_fork_test' line 8 expected OK got $E14#aa [ 13.268969] KGDB: re-enter exception: ALL breakpoints killed [ 13.275099] CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-g82bbb913ffd8 #860 [ 13.282836] Call Trace: [ 13.285313] [c60e1ba0] [c0080ef0] kgdb_handle_exception+0x6f4/0x720 (unreliable) [ 13.292618] [c60e1c30] [c000e97c] kgdb_handle_breakpoint+0x3c/0x98 [ 13.298709] [c60e1c40] [c000af54] program_check_exception+0x104/0x700 [ 13.305083] [c60e1c60] [c000e45c] ret_from_except_full+0x0/0x4 [ 13.310845] [c60e1d20] [c02a22ac] run_simple_test+0x2b4/0x2d4 [ 13.316532] [c60e1d30] [c0081698] put_packet+0xb8/0x158 [ 13.321694] [c60e1d60] [c00820b4] gdb_serial_stub+0x230/0xc4c [ 13.327374] [c60e1dc0] [c0080af8] kgdb_handle_exception+0x2fc/0x720 [ 13.333573] [c60e1e50] [c000e928] kgdb_singlestep+0xb4/0xcc [ 13.339068] [c60e1e70] [c000ae1c] single_step_exception+0x90/0xac [ 13.345100] [c60e1e80] [c000e45c] ret_from_except_full+0x0/0x4 [ 13.350865] [c60e1f40] [c000e11c] ret_from_syscall+0x0/0x38 [ 13.356346] Kernel panic - not syncing: Recursive entry to debugger
This patch creates powerpc specific version of kgdb_arch_set_breakpoint() and kgdb_arch_remove_breakpoint() using patch_instruction()
Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs") Signed-off-by: Christophe Leroy christophe.leroy@c-s.fr Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/kgdb.h | 5 +++- arch/powerpc/kernel/kgdb.c | 43 +++++++++++++++++++++++++++------ 2 files changed, 39 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/kgdb.h b/arch/powerpc/include/asm/kgdb.h index 9db24e77b9f4..a9e098a3b881 100644 --- a/arch/powerpc/include/asm/kgdb.h +++ b/arch/powerpc/include/asm/kgdb.h @@ -26,9 +26,12 @@ #define BREAK_INSTR_SIZE 4 #define BUFMAX ((NUMREGBYTES * 2) + 512) #define OUTBUFMAX ((NUMREGBYTES * 2) + 512) + +#define BREAK_INSTR 0x7d821008 /* twge r2, r2 */ + static inline void arch_kgdb_breakpoint(void) { - asm(".long 0x7d821008"); /* twge r2, r2 */ + asm(stringify_in_c(.long BREAK_INSTR)); } #define CACHE_FLUSH_IS_SAFE 1 #define DBG_MAX_REG_NUM 70 diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c index 35e240a0a408..59c578f865aa 100644 --- a/arch/powerpc/kernel/kgdb.c +++ b/arch/powerpc/kernel/kgdb.c @@ -24,6 +24,7 @@ #include <asm/processor.h> #include <asm/machdep.h> #include <asm/debug.h> +#include <asm/code-patching.h> #include <linux/slab.h>
/* @@ -144,7 +145,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs) if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0) return 0;
- if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr)) + if (*(u32 *)regs->nip == BREAK_INSTR) regs->nip += BREAK_INSTR_SIZE;
return 1; @@ -441,16 +442,42 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code, return -1; }
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) +{ + int err; + unsigned int instr; + unsigned int *addr = (unsigned int *)bpt->bpt_addr; + + err = probe_kernel_address(addr, instr); + if (err) + return err; + + err = patch_instruction(addr, BREAK_INSTR); + if (err) + return -EFAULT; + + *(unsigned int *)bpt->saved_instr = instr; + + return 0; +} + +int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) +{ + int err; + unsigned int instr = *(unsigned int *)bpt->saved_instr; + unsigned int *addr = (unsigned int *)bpt->bpt_addr; + + err = patch_instruction(addr, instr); + if (err) + return -EFAULT; + + return 0; +} + /* * Global data */ -struct kgdb_arch arch_kgdb_ops = { -#ifdef __LITTLE_ENDIAN__ - .gdb_bpt_instr = {0x08, 0x10, 0x82, 0x7d}, -#else - .gdb_bpt_instr = {0x7d, 0x82, 0x10, 0x08}, -#endif -}; +struct kgdb_arch arch_kgdb_ops;
static int kgdb_not_implemented(struct pt_regs *regs) {