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| author |   Christopher M. Riedl <cmr@informatik.wtf> | 2019-04-15 22:26:38 -0500 |
|---|---|---|
| committer |   Michael Ellerman <mpe@ellerman.id.au> | 2019-05-03 02:54:57 +1000 |
| commit | 0acb5f64560a052fd66ab37b212a72964847160f (patch) | |
| tree | 51ab809e5bc5f343e540f4496d2c7af8a60e9847 /arch/powerpc/xmon | |
| parent | powerpc/boot: Fix missing check of lseek() return value (diff) | |
| download | linux-dev-0acb5f64560a052fd66ab37b212a72964847160f.tar.xz linux-dev-0acb5f64560a052fd66ab37b212a72964847160f.zip | |
powerpc/xmon: add read-only mode
Operations which write to memory and special purpose registers should be
restricted on systems with integrity guarantees (such as Secure Boot)
and, optionally, to avoid self-destructive behaviors.
Add a config option, XMON_DEFAULT_RO_MODE, to set default xmon behavior.
The kernel cmdline options xmon=ro and xmon=rw override this default.
The following xmon operations are affected:
memops:
disable memmove
disable memset
disable memzcan
memex:
no-op'd mwrite
super_regs:
no-op'd write_spr
bpt_cmds:
disable
proc_call:
disable
Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
Reviewed-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/xmon')
| -rw-r--r-- | arch/powerpc/xmon/xmon.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index e583ed3f6b93..3e7be19aa208 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 bool xmon_is_ro = IS_ENABLED(CONFIG_XMON_DEFAULT_RO_MODE); static unsigned long adrs; static int size = 1; @@ -202,6 +203,8 @@ static void dump_tlb_book3e(void); #define GETWORD(v) (((v)[0] << 24) + ((v)[1] << 16) + ((v)[2] << 8) + (v)[3]) #endif +static const char *xmon_ro_msg = "Operation disabled: xmon in read-only mode\n"; + static char *help_string = "\ Commands:\n\ b show breakpoints\n\ @@ -989,6 +992,10 @@ cmds(struct pt_regs *excp) memlocate(); break; case 'z': + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } memzcan(); break; case 'i': @@ -1042,6 +1049,10 @@ cmds(struct pt_regs *excp) set_lpp_cmd(); break; case 'b': + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } bpt_cmds(); break; case 'C': @@ -1055,6 +1066,10 @@ cmds(struct pt_regs *excp) bootcmds(); break; case 'p': + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } proccall(); break; case 'P': @@ -1777,6 +1792,11 @@ read_spr(int n, unsigned long *vp) static void write_spr(int n, unsigned long val) { + if (xmon_is_ro) { + printf(xmon_ro_msg); + return; + } + if (setjmp(bus_error_jmp) == 0) { catch_spr_faults = 1; sync(); @@ -2016,6 +2036,12 @@ mwrite(unsigned long adrs, void *buf, int size) char *p, *q; n = 0; + + if (xmon_is_ro) { + printf(xmon_ro_msg); + return n; + } + if (setjmp(bus_error_jmp) == 0) { catch_memory_errors = 1; sync(); @@ -2880,9 +2906,17 @@ memops(int cmd) scanhex((void *)&mcount); switch( cmd ){ case 'm': + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } memmove((void *)mdest, (void *)msrc, mcount); break; case 's': + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } memset((void *)mdest, mval, mcount); break; case 'd': @@ -3792,6 +3826,14 @@ 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_is_ro = false; + } else if (strncmp(p, "ro", 2) == 0) { + xmon_init(1); + xmon_on = 1; + xmon_is_ro = true; } else if (strncmp(p, "off", 3) == 0) xmon_on = 0; else |