Operations which write to memory should be restricted on secure systems and optionally to avoid self-destructive behaviors.
Add a config option, XMON_RO, to control default xmon behavior along with kernel cmdline options xmon=ro and xmon=rw for explicit control. The default is to enable read-only mode. The following xmon operations are affected: memops: disable memmove disable memset memex: no-op'd mwrite super_regs: no-op'd write_spr bpt_cmds: disable proc_call: disable Signed-off-by: cmr <c...@informatik.wtf> --- arch/powerpc/Kconfig.debug | 7 +++++++ arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug index 4e00cb0a5464..33cc01adf4cb 100644 --- a/arch/powerpc/Kconfig.debug +++ b/arch/powerpc/Kconfig.debug @@ -117,6 +117,13 @@ config XMON_DISASSEMBLY to say Y here, unless you're building for a memory-constrained system. +config XMON_RO + bool "Set xmon read-only mode" + depends on XMON + default y + help + Disable state- and memory-altering write operations in xmon. + config DEBUGGER bool depends on KGDB || XMON diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index a0f44f992360..c13ee73cdfd4 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -80,6 +80,7 @@ static int set_indicator_token = RTAS_UNKNOWN_SERVICE; #endif static unsigned long in_xmon __read_mostly = 0; static int xmon_on = IS_ENABLED(CONFIG_XMON_DEFAULT); +static int xmon_ro = IS_ENABLED(CONFIG_XMON_RO); static unsigned long adrs; static int size = 1; @@ -1042,6 +1043,8 @@ cmds(struct pt_regs *excp) set_lpp_cmd(); break; case 'b': + if (xmon_ro == 1) + break; bpt_cmds(); break; case 'C': @@ -1055,6 +1058,8 @@ cmds(struct pt_regs *excp) bootcmds(); break; case 'p': + if (xmon_ro == 1) + break; proccall(); break; case 'P': @@ -1777,6 +1782,9 @@ read_spr(int n, unsigned long *vp) static void write_spr(int n, unsigned long val) { + if (xmon_ro == 1) + return; + if (setjmp(bus_error_jmp) == 0) { catch_spr_faults = 1; sync(); @@ -2016,6 +2024,10 @@ mwrite(unsigned long adrs, void *buf, int size) char *p, *q; n = 0; + + if (xmon_ro == 1) + return n; + if (setjmp(bus_error_jmp) == 0) { catch_memory_errors = 1; sync(); @@ -2884,9 +2896,13 @@ memops(int cmd) scanhex((void *)&mcount); switch( cmd ){ case 'm': + if (xmon_ro == 1) + break; memmove((void *)mdest, (void *)msrc, mcount); break; case 's': + if (xmon_ro == 1) + break; memset((void *)mdest, mval, mcount); break; case 'd': @@ -3796,6 +3812,14 @@ static int __init early_parse_xmon(char *p) } else if (strncmp(p, "on", 2) == 0) { xmon_init(1); xmon_on = 1; + } else if (strncmp(p, "rw", 2) == 0) { + xmon_init(1); + xmon_on = 1; + xmon_ro = 0; + } else if (strncmp(p, "ro", 2) == 0) { + xmon_init(1); + xmon_on = 1; + xmon_ro = 1; } else if (strncmp(p, "off", 3) == 0) xmon_on = 0; else -- 2.21.0