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| author | Jean-Philippe Brucker <jean-philippe@linaro.org> | 2020-06-24 14:22:54 +0300 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-06-24 16:24:29 +0300 |
| commit | 2d21889f8b5c50f65f5162bc972b0b1626b97be2 (patch) | |
| tree | 915213b08f6eb048441ed62ab7ee95f45bf336cb | |
| parent | e56404e8e475c91489b2cca57f2c1b2bc5edf6b2 (diff) | |
| download | linux-2d21889f8b5c50f65f5162bc972b0b1626b97be2.tar.xz | |
arm64: Don't insert a BTI instruction at inner labels
Some ftrace features are broken since commit 714a8d02ca4d ("arm64: asm:
Override SYM_FUNC_START when building the kernel with BTI"). For example
the function_graph tracer:
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
[ 36.107016] WARNING: CPU: 0 PID: 115 at kernel/trace/ftrace.c:2691 ftrace_modify_all_code+0xc8/0x14c
When ftrace_modify_graph_caller() attempts to write a branch at
ftrace_graph_call, it finds the "BTI J" instruction inserted by
SYM_INNER_LABEL() instead of a NOP, and aborts.
It turns out we don't currently need the BTI landing pads inserted by
SYM_INNER_LABEL:
* ftrace_call and ftrace_graph_call are only used for runtime patching
of the active tracer. The patched code is not reached from a branch.
* install_el2_stub is reached from a CBZ instruction, which doesn't
change PSTATE.BTYPE.
* __guest_exit is reached from B instructions in the hyp-entry vectors,
which aren't subject to BTI checks either.
Remove the BTI annotation from SYM_INNER_LABEL.
Fixes: 714a8d02ca4d ("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200624112253.1602786-1-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
| -rw-r--r-- | arch/arm64/include/asm/linkage.h | 6 |
1 files changed, 0 insertions, 6 deletions
diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h index 81fefd2a1d02..ba89a9af820a 100644 --- a/arch/arm64/include/asm/linkage.h +++ b/arch/arm64/include/asm/linkage.h @@ -12,7 +12,6 @@ * instead. */ #define BTI_C hint 34 ; -#define BTI_J hint 36 ; /* * When using in-kernel BTI we need to ensure that PCS-conformant assembly @@ -43,11 +42,6 @@ SYM_START(name, SYM_L_WEAK, SYM_A_NONE) \ BTI_C -#define SYM_INNER_LABEL(name, linkage) \ - .type name SYM_T_NONE ASM_NL \ - SYM_ENTRY(name, linkage, SYM_A_NONE) \ - BTI_J - #endif /* |