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author | andrew <andrew@FreeBSD.org> | 2013-05-19 16:25:09 +0000 |
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committer | andrew <andrew@FreeBSD.org> | 2013-05-19 16:25:09 +0000 |
commit | 0e0a417d2bcaf3630559ef3ff0ba356da3a6f4b4 (patch) | |
tree | 458457d6b04eba723811d3b685e04907205b541e /sys/arm | |
parent | cd30dfafe0c269299f5800713f71069edf694b0d (diff) | |
download | FreeBSD-src-0e0a417d2bcaf3630559ef3ff0ba356da3a6f4b4.zip FreeBSD-src-0e0a417d2bcaf3630559ef3ff0ba356da3a6f4b4.tar.gz |
Add a comment explaining why stack_capture is empty for EABI and clang.
While here add a comment pointing out that, while r11 is not the frame
pointer on EABI as there is no frame pointer, it's value is unused so is
safe.
Diffstat (limited to 'sys/arm')
-rw-r--r-- | sys/arm/arm/stack_machdep.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/sys/arm/arm/stack_machdep.c b/sys/arm/arm/stack_machdep.c index d335934..36a776a 100644 --- a/sys/arm/arm/stack_machdep.c +++ b/sys/arm/arm/stack_machdep.c @@ -36,6 +36,13 @@ __FBSDID("$FreeBSD$"); #include <machine/pcb.h> #include <machine/stack.h> +/* + * This code makes assumptions about the stack layout. These are correct + * when using APCS (the old ABI), but are no longer true with AAPCS and the + * ARM EABI. There is also an issue with clang and llvm when building for + * APCS where it lays out the stack incorrectly. Because of this we disable + * this when building for ARM EABI or when building with clang. + */ static void stack_capture(struct stack *st, u_int32_t *frame) { @@ -61,6 +68,11 @@ stack_save_td(struct stack *st, struct thread *td) if (TD_IS_RUNNING(td)) panic("stack_save_td: running"); + /* + * This register, the frame pointer, is incorrect for the ARM EABI + * as it doesn't have a frame pointer, however it's value is not used + * when building for EABI. + */ frame = (u_int32_t *)td->td_pcb->un_32.pcb32_r11; stack_zero(st); stack_capture(st, frame); |