| Message ID | 20200807004904.72893-1-linux@roeck-us.net (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 9bceb80b3cc483e6763c39a4928402fa82815d3e |
| Headers | show |
| Series | arm64: kaslr: Use standard early random function | expand |
On Thu, Aug 6, 2020 at 5:49 PM Guenter Roeck <linux@roeck-us.net> wrote: > > Use arch_get_random_seed_long_early() instead of arm64 specific functions > to solve the problem. As a side effect of this change, the code no longer > bypasses ARCH_RANDOM, which I consider desirable (after all, ARCH_RANDOM > was disabled for a reason). This patch looks sane to me, but let's see what the arm64 people say in case they have preferences.. Linus
Hi Guenter, On Thu, Aug 06, 2020 at 05:49:04PM -0700, Guenter Roeck wrote: > Commit 585524081ecd ("random: random.h should include archrandom.h, not > the other way around") tries to fix a problem with recursive inclusion > of linux/random.h and arch/archrandom.h for arm64. Unfortunately, this > results in the following compile error if ARCH_RANDOM is disabled. > > arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init': > arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function > '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? > [-Werror=implicit-function-declaration] > if (__early_cpu_has_rndr()) { > ^~~~~~~~~~~~~~~~~~~~ > __early_pfn_to_nid > arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function > '__arm64_rndr' [-Werror=implicit-function-declaration] > if (__arm64_rndr(&raw)) > ^~~~~~~~~~~~ > > Problem is that arch/archrandom.h is only included from linux/random.h if > ARCH_RANDOM is enabled. If not, __arm64_rndr() and __early_cpu_has_rndr() > are undeclared, causing the problem. > > Use arch_get_random_seed_long_early() instead of arm64 specific functions > to solve the problem. As a side effect of this change, the code no longer > bypasses ARCH_RANDOM, which I consider desirable (after all, ARCH_RANDOM > was disabled for a reason). There's no bypass of ARCH_RANDOM; the bits KASLR depends on are empty stubs when ARCH_RANDOM is not selected. I added the common early functions after this code was written. > Reported-by: Qian Cai <cai@lca.pw> > Fixes: 585524081ecd ("random: random.h should include archrandom.h, not the other way around") This is where things broke; there was no need to change kaslr.c's include of <asm/archrandom.h>, since kaslr.c only depends on the RNDR bits defined there./ > Fixes: 2e8e1ea88cbc ("arm64: Use v8.5-RNG entropy for KASLR seed") I don't think this tag is necessary; this commit built and worked fine, and there wasn't any ARCH_RANDOM bypass to speak of. > Cc: Qian Cai <cai@lca.pw> > Cc: Mark Brown <broonie@kernel.org> > Signed-off-by: Guenter Roeck <linux@roeck-us.net> This patch itself looks fine, but as above I think the commit message is misleading w.r.t. bypassing ARCH_RANDOM, and the second fixes tag isn't necessary. With those bits gone: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/kernel/kaslr.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c > index 9ded4237e1c1..b181e0544b79 100644 > --- a/arch/arm64/kernel/kaslr.c > +++ b/arch/arm64/kernel/kaslr.c > @@ -84,6 +84,7 @@ u64 __init kaslr_early_init(u64 dt_phys) > void *fdt; > u64 seed, offset, mask, module_range; > const u8 *cmdline, *str; > + unsigned long raw; > int size; > > /* > @@ -122,15 +123,12 @@ u64 __init kaslr_early_init(u64 dt_phys) > } > > /* > - * Mix in any entropy obtainable architecturally, open coded > - * since this runs extremely early. > + * Mix in any entropy obtainable architecturally if enabled > + * and supported. > */ > - if (__early_cpu_has_rndr()) { > - unsigned long raw; > > - if (__arm64_rndr(&raw)) > - seed ^= raw; > - } > + if (arch_get_random_seed_long_early(&raw)) > + seed ^= raw; > > if (!seed) { > kaslr_status = KASLR_DISABLED_NO_SEED; > -- > 2.17.1 >
On Thu, Aug 06, 2020 at 05:49:04PM -0700, Guenter Roeck wrote: > Use arch_get_random_seed_long_early() instead of arm64 specific functions > to solve the problem. As a side effect of this change, the code no longer > bypasses ARCH_RANDOM, which I consider desirable (after all, ARCH_RANDOM > was disabled for a reason). This should be fine since the entire implementation is still static inline in the header other than the prints in the WARN_ON() which should never be triggered here so it should be fine. Reviewed-by: Mark Brown <broonie@kernel.org> Tested-by: Mark Brown <broonie@kernel.org>
On 8/7/20 3:17 AM, Mark Rutland wrote: > Hi Guenter, > > On Thu, Aug 06, 2020 at 05:49:04PM -0700, Guenter Roeck wrote: >> Commit 585524081ecd ("random: random.h should include archrandom.h, not >> the other way around") tries to fix a problem with recursive inclusion >> of linux/random.h and arch/archrandom.h for arm64. Unfortunately, this >> results in the following compile error if ARCH_RANDOM is disabled. >> >> arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init': >> arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function >> '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? >> [-Werror=implicit-function-declaration] >> if (__early_cpu_has_rndr()) { >> ^~~~~~~~~~~~~~~~~~~~ >> __early_pfn_to_nid >> arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function >> '__arm64_rndr' [-Werror=implicit-function-declaration] >> if (__arm64_rndr(&raw)) >> ^~~~~~~~~~~~ >> >> Problem is that arch/archrandom.h is only included from linux/random.h if >> ARCH_RANDOM is enabled. If not, __arm64_rndr() and __early_cpu_has_rndr() >> are undeclared, causing the problem. >> >> Use arch_get_random_seed_long_early() instead of arm64 specific functions >> to solve the problem. As a side effect of this change, the code no longer >> bypasses ARCH_RANDOM, which I consider desirable (after all, ARCH_RANDOM >> was disabled for a reason). > > There's no bypass of ARCH_RANDOM; the bits KASLR depends on are empty > stubs when ARCH_RANDOM is not selected. I added the common early > functions after this code was written. > >> Reported-by: Qian Cai <cai@lca.pw> >> Fixes: 585524081ecd ("random: random.h should include archrandom.h, not the other way around") > > This is where things broke; there was no need to change kaslr.c's > include of <asm/archrandom.h>, since kaslr.c only depends on the RNDR > bits defined there./ > Problem is that, prior to the above patch, asm/archrandom.h used to include linux/random.h, which resulted in a recursion. That only worked because some other include file had already included linux/random.h in kaslr.c. In v5.7.y, with gcc 7.x and older, that include did not happen, causing a compile failure. In file included from ./arch/arm64/include/asm/archrandom.h:9:0, from arch/arm64/kernel/kaslr.c:14: ./include/linux/random.h: In function ‘arch_get_random_seed_long_early’: ./include/linux/random.h:149:9: error: implicit declaration of function ‘arch_get_random_seed_long’ >> Fixes: 2e8e1ea88cbc ("arm64: Use v8.5-RNG entropy for KASLR seed") > > I don't think this tag is necessary; this commit built and worked fine, > and there wasn't any ARCH_RANDOM bypass to speak of. > >> Cc: Qian Cai <cai@lca.pw> >> Cc: Mark Brown <broonie@kernel.org> >> Signed-off-by: Guenter Roeck <linux@roeck-us.net> > > This patch itself looks fine, but as above I think the commit message is > misleading w.r.t. bypassing ARCH_RANDOM, and the second fixes tag isn't > necessary. > You are correct. I'll change that and resubmit. Thanks, Guenter > With those bits gone: > > Reviewed-by: Mark Rutland <mark.rutland@arm.com> > > Mark. > >> --- >> arch/arm64/kernel/kaslr.c | 12 +++++------- >> 1 file changed, 5 insertions(+), 7 deletions(-) >> >> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c >> index 9ded4237e1c1..b181e0544b79 100644 >> --- a/arch/arm64/kernel/kaslr.c >> +++ b/arch/arm64/kernel/kaslr.c >> @@ -84,6 +84,7 @@ u64 __init kaslr_early_init(u64 dt_phys) >> void *fdt; >> u64 seed, offset, mask, module_range; >> const u8 *cmdline, *str; >> + unsigned long raw; >> int size; >> >> /* >> @@ -122,15 +123,12 @@ u64 __init kaslr_early_init(u64 dt_phys) >> } >> >> /* >> - * Mix in any entropy obtainable architecturally, open coded >> - * since this runs extremely early. >> + * Mix in any entropy obtainable architecturally if enabled >> + * and supported. >> */ >> - if (__early_cpu_has_rndr()) { >> - unsigned long raw; >> >> - if (__arm64_rndr(&raw)) >> - seed ^= raw; >> - } >> + if (arch_get_random_seed_long_early(&raw)) >> + seed ^= raw; >> >> if (!seed) { >> kaslr_status = KASLR_DISABLED_NO_SEED; >> -- >> 2.17.1 >>
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index 9ded4237e1c1..b181e0544b79 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -84,6 +84,7 @@ u64 __init kaslr_early_init(u64 dt_phys) void *fdt; u64 seed, offset, mask, module_range; const u8 *cmdline, *str; + unsigned long raw; int size; /* @@ -122,15 +123,12 @@ u64 __init kaslr_early_init(u64 dt_phys) } /* - * Mix in any entropy obtainable architecturally, open coded - * since this runs extremely early. + * Mix in any entropy obtainable architecturally if enabled + * and supported. */ - if (__early_cpu_has_rndr()) { - unsigned long raw; - if (__arm64_rndr(&raw)) - seed ^= raw; - } + if (arch_get_random_seed_long_early(&raw)) + seed ^= raw; if (!seed) { kaslr_status = KASLR_DISABLED_NO_SEED;
Commit 585524081ecd ("random: random.h should include archrandom.h, not the other way around") tries to fix a problem with recursive inclusion of linux/random.h and arch/archrandom.h for arm64. Unfortunately, this results in the following compile error if ARCH_RANDOM is disabled. arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init': arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? [-Werror=implicit-function-declaration] if (__early_cpu_has_rndr()) { ^~~~~~~~~~~~~~~~~~~~ __early_pfn_to_nid arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function '__arm64_rndr' [-Werror=implicit-function-declaration] if (__arm64_rndr(&raw)) ^~~~~~~~~~~~ Problem is that arch/archrandom.h is only included from linux/random.h if ARCH_RANDOM is enabled. If not, __arm64_rndr() and __early_cpu_has_rndr() are undeclared, causing the problem. Use arch_get_random_seed_long_early() instead of arm64 specific functions to solve the problem. As a side effect of this change, the code no longer bypasses ARCH_RANDOM, which I consider desirable (after all, ARCH_RANDOM was disabled for a reason). Reported-by: Qian Cai <cai@lca.pw> Fixes: 585524081ecd ("random: random.h should include archrandom.h, not the other way around") Fixes: 2e8e1ea88cbc ("arm64: Use v8.5-RNG entropy for KASLR seed") Cc: Qian Cai <cai@lca.pw> Cc: Mark Brown <broonie@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- arch/arm64/kernel/kaslr.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)